In this section of the book we dig deeper into the major control methods discussed in chapters 1–4. You will be reminded as to whether the control is used to battle nutrient deficiencies, pests or diseases and be given specific instruction on how to use each control. Many solutions listed here can be used for more than one problem.
Outdoors, I use the term “control” to mean the elimination of noticeable damage to plants. Indoors, except in certain predator/prey situations, it means the elimination of the problem.
All of the controls listed here are safe to use for herb or for edible crops. Sprays are washed away by water, including rain, so plan to reapply spray products after rain or any watering that hits the affected areas of the plants. There are no products with hard-to-pronounce ingredients or with names that are a compilation of chemical terms. Most of the solutions use nature-designed chemistry (mostly plant oils) or natural processes to protect your garden.
Integrated Pest Management combines the practice of pest and disease prevention, as well as planning protocols beforehand, with regular horticultural practices. The thinking is to consider pests and disease with every step you take as you garden.
Take into account biological controls first, organic or natural pesticides second and industrial pesticides or chemical controls third. It is important to note that in situations like full-blown mite infestation, the protocols you choose can and should be immediately moved forward to the chemical control phase. The idea is to consider the most beneficial outcome with the least amount of environmental impact. Sometimes that means stage 3 immediately because stages 1 and 2 will drag you into deeper waters.
In nurseries and greenhouses, an IPM chart or binder is often located with work logs or MSDS sheets. You probably don’t need to write out a formal IPM plan especially because most of the meat is usually pest-specific as well as site and control protocol-specific. This book does a lot of that for you so realistically most growers can focus on planning safe and effective strategies to navigate most of the troubles commonly encountered. Practice at this will build a gardener’s skills in dealing with new problems, pests or diseases on the fly.
General IPM checklists usually provide growers with a guide on how to conduct their search for garden issues as well as these specific protocols and counter-measure implementation plans. They all kind of go something like:
Step 1 Observe the environment.
Step 2 If temperature, humidity and irrigation are within range, inspect plants for vectors or symptoms.
Step 3 If you don’t see no pests or symptoms, commence daily duties.
Step 4 If during daily gardening you notice a vector or symptom, then implement IPM procedures accordingly.
The pests, diseases, prevention techniques and control measures are all here in the guide for you to quickly access and use. When going through the motions, please consider Integrated Pest Management as a way to maximize efficiency in identifying problems quickly as well as taking the path of lesser environmental impact.
Always read the label carefully before buying or using any control product. You need to follow the manufacturer’s directions carefully to use these products safely and avoid harming the plants. You also need to identify the ingredients in a product to be sure that it will treat the problem you’re dealing with and will not introduce additional problems you don’t want. Many modern garden products seek to be all-in-one cures for common garden problems, for example, a micronutrient fertilizer that also contains high levels of nitrogen. Others apply more than one control for the same problem, such as a pyrethrum product that also contains rotenone or piperonyl butoxide. If that’s what you need for your situation, fine, but check the label to avoid surprises.
If you are applying any product that you have never used before, including a new homemade recipe, always test it on a few branches of a plant and wait a day or two before applying it to your entire garden.
These are granulated products made from pressed alfalfa hay and the solids remaining after cotton seeds are pressed for oil. They are high in nitrogen and can be added to soil or planting mix as slow-release nitrogen fertilizers.
Look for alfalfa and cottonseed meals at farm animal feed stores and garden centers under many different brands.
Ampelomyces Quisqualis is a hyperparasite that targets a few fungi, but for the purposes of cannabis cultivation, is effective against powdery mildew. It infects mildew colonies, slowing their growth and in some cases eliminates them completely. AQ occurs naturally and is generally endemic to the same places as powdery mildew, minimizing the potential for adverse affects on beneficial organisms. AQ has been extensively tested for agriculture. It has no phytotoxicity and is harmless to humans and beneficial organisms. AQ can be applied on its own but can also be found in several commercially produced organic fungicides.
These products contain a poison such as boric acid, arsenic or sulfluramid and an attractive bait that entices the ants to carry it back to their nest, where it kills both workers and queens.
Ant baits and ant stakes are very safe methods of dealing with the problem because they use minute amounts of poison in a very targeted way.
The ingredients are not released into the general environment. Instead, the target acquires the slow acting poisons. The affected ants have time to interact with a large number of nest mates so the poison affects a large group. Available in many brands, including Grants Ant Stakes, Terro Liquid Borate Ant Bait, Enforcer Ant Bait, Advance® Dual-Choice Bait Station and Drax Liquidator® Ant Bait Station.
In addition to the direct harm caused to soil condition by tunneling and nesting, ants are notorious for “aphid ranching:” Ants can extract nutrients from aphid excretions and a colony will ferociously protect its aphid “stable” from natural predators. Organic ant baits usually contain Borax, a mineral salt of Boric Acid, which slowly kills ants, allowing time for distribution to the entire colony. It is a natural mineral with minimal toxicity to humans.
Aphidoletes aphidimyza is a small fly (2–3 mm long or .7-.11 in) that looks a little like a mosquito. The larvae are bright orange and are attracted to the smell of honeydew. They attack and consume aphids by the score.
Midge larvae paralyze aphids with an injection of biotoxin to the legs, allowing them to bore a hole in the unfortunate aphid’s thorax and suck out the viscera, leaving behind an empty husk. Aphid midges often kill more aphids than they can eat when faced with an especially dense population, making them an excellent control. They’re sold as pupae, which can be placed inside a greenhouse or at the center of a field where they will grow into an adult population and lay eggs among the aphids. Using aphid midges in conjunction with parasitic nematodes is not recommended because the nematodes may target pupae.
Buy them as pupae from companies such as Buglogical, Planet Natural, Hydro-Gardens, Natural Insect Control, Peaceful Valley and EcoSolutions. The pupae hatch into adults, which lay eggs and produce the aphid-destroying larvae. Plan on using about 100 pupae per 100 square feet.
Bacillus pumilus is a naturally occurring bacterium that produces compounds that kill active fungal infections and inhibit further growth. Strain QST 2808 of this bacterium has been patented for use as a biorational fungicide against Fusarium, gray mold and powdery mildew, under the brand name Sonata®. It is most effective when applied as a preventive measure before symptoms appear.
Sonata® is effective for about 10 days after each application. I found that it does not completely eliminate powdery mildew when used alone, but it does work very well in conjunction with Bacillus subtilis fungicides such as Serenade®.
Bacillus subtilis is another naturally occurring fungicidal bacterium. Several strains of this bacterium have been patented for use against Fusarium, gray mold, powdery mildew, Pythium and Verticillium under brand names such as Serenade®, Rhizopro® and Subtilex®. It is most effective when applied as a preventive measure before symptoms appear.
Bacillus subtilis colonizes the soil around plant roots and produces antibiotics that suppress the fungi causing root and stem rot. B. subtilis is used as a seed treatment or soil drench. It works better as a preventative, and will not control a serious damping off infestation after it has begun The Bacillus subtilis strain (QST713) is known by the brand name Serenade, is particularly effective against powdery mildew. It uses three chemical pathways to destroy disease causing pathogens. It stops harmful spores from germinating, disrupts growth of the germ tube and mycelia, and inhibits the growth of the fungus at the leaf surface. It is considered totally safe to humans and animals since the bacteria attacks only fungi. Watch out if you are a fungus. Otherwise you are safe. This bacterium is marketed under several names, including Companion and Serenade.
Bacillus Thuringiensis is a family of bacteria with at least 35 separate strains producing 140 types of spore toxins, the real weapons against pests. Two common BT strains are described here because they contain spore toxins that are active against some common cannabis pests, as well as beetle grubs, fly larvae, and many other soil dwelling insects.
Bacillus thuringiensis (variety israelensis) (Indoors and Outdoors)
This spore toxin exists in the bacteria as a crystalline protein. When a fungus gnat ingests a spore, the protein is dissolved by enzymes in the insect’s digestive tract and destroys the cells of the insect’s digestive system. Once the spores are ingested, insects stop feeding within an hour. They shrivel, blacken, and die. Bacillus thuringiensis Israelensis does not reproduce in pest populations, so it must be reapplied every week to 10 days. The dust is applied to the surface of the soil or rockwool. Bacillus thuringiensis Israelensis is compatible with some other biocontrol agents, including the beneficial nematode Steinernema sp. and the soil mite Hypoaspis miles. It is marketed as Gnatrol and Bactimos.
Bacillus thuringiensis (var. kurstaki) is one of the best solutions for caterpillars. Bacillus thuringiensis kurstaki is a naturally occurring soil bacterium that has been used since the 1930s. It acts selectively, killing caterpillars, but poses no harm to beneficial insects, earthworms, fish, birds, cats, dogs, other mammals, or humans. Bacillus thuringiensis kurstaki renders the caterpillars’ stomachs nonfunctional by multiplying inside the digestive tract, creating sharp, toxic, protein crystals.
Bacillus thuringiensis kurstaki does not attack Lepidoptera eggs, but it works well on caterpillars that are chomping on leaves, especially if they are in the earliest stages of caterpillar life. Once the leaves have been sprayed with Bacillus thuringiensis kurstaki, only caterpillars that eat the treated areas will be affected. Bacillus thuringiensis kurstaki affects insects quickly, causing caterpillars to stop eating soon after they’ve fed on treated plants. Death follows in a day or two. The decaying caterpillar body releases more of the bacteria. Given the lengthy commercial use of this Bacillus thuringiensis strain, there is some concern about caterpillar resistance. There are no known incidences of developed resistance to Bacillus thuringiensis kurstaki among caterpillars. Bacillus thuringiensis kurstaki comes in liquid and wettable powder form. A single application provides permanent protection until it is washed off, so reapply after rain. Bacillus thuringiensis kurstaki breaks down over three to seven days. Since this product works best on young caterpillars, multiple treatments are necessary to eradicate all caterpillars from staggered hatch times. If product instructions call for dilution with water, use non-chlorinated water because chlorine in tap water can destroy the Bacillus thuringiensis kurstaki bacteria, thus rendering the treatment useless. Bacillus thuringiensis kurstaki is widely available in garden stores and through the Internet. Brands include Green Step Caterpillar Control, Dipel Dust, and Bonide BT, Thuricide. Make sure that the ingredient label of any other brand does not list additional chemical pesticides.
Barley straw rafts floating in the water are algaecidal. They are useful in hydroponic systems and reservoirs. This effect is due to hydrogen peroxide produced by a complex series of chemical reactions as the barley decays.
Algae control is a problem for hydroponic growers because it taxes the oxygen resources of the water. Barley straw rafts have been successfully used as an algae control method in large bodies of water like lakes and ponds, however this method is slow and still requires high enough water oxygenation to maintain aerobic decomposition. Barley straw extract can inhibit the growth of algae and is sold as a liquid.
Beauveria bassiana is a fungus that attacks and kills a variety of pests, including aphids, caterpillars, leaf miners, spider mites and whiteflies. Note that many beneficial insects, such as lady beetles, are also susceptible. Products containing Beauveria work by contact but take three to seven days to germinate, penetrate and kill target pests. Infected insects stop eating soon after and die in two to 10 days. The fungus’ reproductive organs emerge from the corpse as a white mat (hence the name white muscardine disease) and produce spores. B. bassiana does best at 90 percent humidity but works well in the grow room humidity range of 40% - 60 %, with daytime temperatures of 70 to 86 F. Spores do not have to be ingested to work. Spray plants thoroughly as soon as you identify an infestation. In addition to killing off existing pests, it prevents infestation or reinfestation. Spray on all surfaces of infested plants and the medium. Once it establishes in a space, it helps to keep infestations from occurring. Commercial products containing B. bassiana include Naturalis H&G®, Mycotrol® and Botanigard®.
Boric acid is one of the best cures for boron deficiencies as well as a common, safe and effective ant poison. It is also effective against cockroaches and termites. It can be sprinkled as a powder or laid down as a barrier wherever pests are seen, but it is usually more effective laced into a bait.
The powder sticks to ants’ exoskeletons as they walk through a perimeter barrier. When the ants clean themselves, they lick it off, and ingest it. The acid activates as it moistens and it eats the ants’ internal organs. Because of its toxicity to ants, it is effective as a food-based pesticide and as a barrier. When ants come in contact with enough of it, it clings to their exoskeletons and desiccates them. Boric acid is safe for bees and birds and it is considered non-hazardous to mammals. Many commercial baits are available, including Drax®, Ant Kil Gel, Borid® and Dr. Moss® Liquid Ant Bait.
You can make your own with these recipes:
Sugar Bait
1 cup sugar
4 teaspoons boric acid
Grease Bait
3 cups water
about 1 cup canned cat food
1 tablespoon boric acid
Mix the ingredients and put small amounts of the solution or cat food mixture in shallow dishes near plants. Keep these baits out of reach of pets and children.
These nutrient supplements contain both calcium and magnesium, suitable for correcting deficiencies in either or both of these minerals. Brands include Botanicare® Cal-Mag Plus®, Sensi- Cal®, MagiCal® and Cal-Max®.
Note that different Cal-Mag products contain different levels of nitrogen, phosphorous and potassium, the big three macronutrients. Check the label on the product you’re thinking of using, and avoid using high-nitrogen products during flowering or high-phosphorous products during vegetative growth.
Magnesium is a secondary nutrient that plays a crucial role in photosynthesis, making magnesium deficiency a potentially lethal issue for cannabis plants. Calcium is another secondary nutrient, but it is immobile, which means the plant requires a constant supply and cannot draw on stores in older leaves. Formulations of calcium and magnesium are available separately, but many growers prefer Cal-mag products, which when added to your nutrition plan can prevent any deficiencies in the first place.
Various compounds such as calcium nitrate (CaNO3) and calcium acetate (CaCH3CO2) are used to correct calcium deficiencies. Calcium nitrate is especially useful as it provides both calcium and nitrogen in readily available forms. It can be purchased at larger garden centers under the Viking fertilizer brand and through scientific supply houses under brand names such as Aldrich and Sigma.
Beware of using calcium nitrate during the flowering stage because it will provide more nitrogen than the plant should have at that stage of growth.
Calcium nitrate is an inorganic salt that contains high levels of calcium and dissolves easily in water, making it an excellent option for addressing calcium deficiency in cannabis plants. It should not be used during flowering as it will boost the nitrogen levels too high.
This is the substance that gives hot peppers their heat. Pepper plants produce capsaicin for its repellent value against insects and other animals that might otherwise eat the plants. It provides similar protection when applied to other plants.
Cayenne pepper contains capsaicin, and it can be sprinkled as a powder to repel ants.
You can make an insecticidal pepper spray with this recipe:
1/2 ounce (15 g) dried or 4 ounces (60 g) fresh peppers (habañero or other very hot pepper)
2 tablespoons (30 mL) of vegetable oil
1/4 teaspoon (1 g) lecithin granules
1/4 teaspoon (1 g) wetting agent
Water to make up one pint (450 ml)
You can also substitute 2 tablespoons (30 mL) of Asian hot pepper oil for peppers. Wear gloves whenever you handle peppers or pepper oil, and avoid touching your eyes or mouth with your gloved hands. Grind the peppers (do not discard the seeds) and oil together in a blender. Add the lecithin granules, wetting agent and water, and mix thoroughly. The mixture can be used immediately but will become stronger if the peppers are allowed to soak. Strain the mixture through cheesecloth or panty hose into a glass jar for storage. Label the jar “Pepper Spray Concentrate.” To use, mix 1 or 2 tablespoons (15–30 mL) of this concentrate with 1 pint of water and spray on plants.
As with all home recipes, test this spray on a few leaves and wait a day to check for damage, before applying it to your whole garden.
Commercial products that contain capsaicin include Hot Pepper Spray®, Bonide® Hot Pepper Wax for ants, aphids, leaf miners, spider mites, thrips and whiteflies), Repellex® Mole, Vole and Gopher Repellent (for gophers and moles), Browseban® and Liquid Fence® (for deer).
Plants use carbon dioxide (CO2) for photosynthesis, and it is present in the atmosphere at 300–400 parts per million (ppm). Growers often use CO2 tanks to increase the levels of this gas to 1,500–2,000 ppm in their grow rooms and greenhouses. These levels are not harmful to most animal life. However, increasing the carbon dioxide level to 10,000 ppm (1%) and holding it at that level for an hour kills most insects, including aphids, spider mites, thrips and whiteflies. Take care to vent the room thoroughly after this treatment, as such high levels of CO2 are hazardous for humans as well.
CO2 is also useful against ants, gophers and moles. Against ants, pour 1 gallon of seltzer water into the anthill, or inject CO2 into the nest from a tank, using a wand. Against gophers or moles, drop 8 to 16 ounces (225 to 450 grams) of dry ice into the tunnel, or deliver a similar amount of CO2 from a tank.
Carbon dioxide is crucial for proper plant development, and increasing it will boost plant vigor and resistance to heat. A CO2 generator is one option for increasing levels, but it will also produce heat, making it impractical for small indoor or greenhouse grows. For a temperature neutral option that allows for slightly more control, compressed CO2 can be used to release CO2 from above and fans can be used to circulate it. The atmosphere usually contains around 400ppm or CO2 and cannabis tends to thrive when that number is between 1,000 and 2,000ppm, but keep in mind that above 3,000ppm CO2 presents a potentially deadly danger to humans.
This is a popular ingredient in gopher and mole repellents. It repels by both taste and smell. The liquid can be smeared on paper and dropped into the gopher’s burrow. Commercial repellents such as Repellex® Mole, Vole and Gopher Repellent, Molemax® and Sweeney’s® Mole & Gopher Repellent may be easier to use.
Chelation is a chemical process whereby nutrient minerals (such as boron, copper, iron, magnesium, manganese, zinc and others) are made more available to plants by combining them with a compound such as citric acid or EDTA (ethylenediaminetetraacetic acid). Many hydroponic micronutrient formulas contain a blend of chelated minerals. Other products contain single metal chelates for treating specific deficiencies. Brands depend on the specific mineral of interest:
Copper: LibrelTM Copper Chelate, YEOMAN® 5% Cu
Iron: Bonide Liquid Iron (also contains Zn and Mn), Plant-Prod® Iron Chelate
Manganese: Growth Product Manganese Chelate, LibrelTM Manganese Chelate
Zinc: YEOMAN® 7% Zn, Nulex® Liquid Zinc
Soil conditioners like humic and fulvic acid will encourage chelation in any grow medium.
This is one of the more modern rat poisons, developed because it is significantly less toxic to humans than it is to rats and mice. Of course all rat poisons should be treated with care and deployed only in tamper-proof bait stations. Commercial baits such as Quintox® and Campaign® are effective.
This form of Vitamin D is lethal to rats and mice that are resistant to anti-coagulants. It’s a one time feeding bait that kills rodents through hypercalcemia, leaving minimal secondary toxicity in their tissues because of its rapid efficacy. It had a low toxicity to birds.
Cinnamon destroys powdery mildew, with an effectiveness rate of 50–70%. It doesn’t eradicate mildew completely, but it keeps the mildew in check. It also potentiates other suppressive sprays so it is good to use cinnamon and sprays in combination with other methods of control. In addition to its fungicidal properties, cinnamon is effective against ants, aphids, fungus gnats, spider mites, thrips and whiteflies.
Mix food grade oil (available at herb shops and natural food stores) at the rate of 1 part to 200 parts water or a bit under 1 teaspoon (5 mL) per quart (950 mL). Or make a tea directly from cinnamon: boil water, turn off the heat and let cool for a few minutes, then add 1 ounce of cinnamon to 1/2 pints water. Let the tea cool to room temperature. Add half a pint of 100 proof grain alcohol or rubbing alcohol and let sit. Strain the cinnamon. The spray is ready to use. A faster method is to add 2 teaspoons (10 mL) cinnamon oil to 1 pint (500 mL) of water and add a dash of castile soap. Rosemary oil and thyme oil are also sometimes combined with cinnamon oil. The solution should consist of no more than 0.75% total oil.
Repel ants with cinnamon powder, either alone or mixed 50/50 with diatomaceous earth. Sprinkle the powder wherever you find ants entering.
Ed Rosenthal’s Zero Tolerance® contains cinnamon oil in both its pesticide and fungicide formulations. Dr. Earth® Pro-ActiveTM Fruit and Vegetable Insect Spray, Cinnacure® and FlowerPharmTM are other brand-name preparations.
Clove oil is used in some botanical fungicides. Eugenol, a component of clove oil, is both a fungicide and a potent contact insecticide. It has virtually no residual activity, although the scent lingers. Eugenol is considered a minimum risk ingredient of pesticides. It has very low risk of damage to the environment or user. It is effective against ants, aphids, caterpillars, Fusarium, gray mold, Pythium, spider mites and thrips.
Ed Rosenthal’s Zero Tolerance® contains clove oil in both its pesticide and fungicide formulations. Dr. Earth® Pro-ActiveTM Fruit and Vegetable Insect Spray, Phyta-Guard EC, GC-Mite®, Natura Bug-A-Tak® and Bioganic® Lawn and Garden Spray are also commercial clove oil preparations.
Compost is rich black material similar to soil, produced by the controlled decomposition of organic materials (vegetable scraps, yard waste, etc.). You can buy it at garden centers, or make your own. It is a rich source of beneficial microbes and micronutrients and provides many benefits to improve overall plant health. The beneficial microbes in compost act as barriers to infection and also destroy pathogenic organisms.
It can be worked into the soil or incorporated into a container planting mix before planting, and it can be prepared as a tea and applied by irrigation or foliar spray. Compost tea requires special care in hydroponic systems. It presents no difficulties as a foliar spray, but it should be added to the nutrient solution only in drip-to-drain systems and should be thoroughly filtered before use.
Some hydroponic shops prepare compost tea on the premises and sell it fresh. They also sell kits under brands such as SoilSoup and Vermicorp to enable home users to make their own. To prepare your own tea, you can use one of these kits, or assemble a bucket, an aquarium air pump (with hose and “bubbler” attached), a nylon stocking and enough compost to fill the bucket about one-quarter full. Buckets larger than 1 gallon (4 L) may require more bubblers for adequate aeration.
Load the compost into the stocking to make a “compost teabag.” Tie the end of the stocking to the bucket handle and put the bag in the bucket. Some compost tea recipes call for molasses. However, this encourages the growth of E. coli and other pathogenic bacteria. Fill the bucket with water and put the air hose and bubbler from the pump at the bottom of the bucket. Run the bubbler to keep the solution aerated for about a day. Switch off the pump and let the tea settle. The liquid in the bucket should be deep brown, with no unpleasant smell. A smell of ammonia or rot means that the tea has become anaerobic and should not be used as a foliar spray.
Compost tea must be used as quickly as possible because it turns anaerobic within a few hours after aeration stops. Strain the liquid through a cheesecloth strainer or filter and apply as a foliar spray or add it to your irrigation water. The used compost can be spread on the surface of the soil around the plants.
Compost and compost tea are “tonics” that promote plant health and help to prevent disease, not specific cures for any pathogen. The effectiveness of these preparations depends greatly on how they’re made, but well-made compost can do a lot to produce healthy plants.
Copper has been used as a fungicide for centuries. However, ingestion of copper is hazardous to humans and pets, and it is not permitted in some states. Spraying it can lead to ingestion, which has health consequences. Don’t use this substance Copper fungicides are implicated in toxicological problems of farm workers who are in contact with them. Cannabis treated with copper is inhale or ingest.
Copper has numerous applications for agriculture, but its most common use for cannabis is the creation of a Bordeaux Mixture, which is comprised of equal parts copper sulfate and calcium oxide from slaked lime and used as a fungicide.
A 2- to 4-inch-wide circular strip of copper reacts chemically with the slug or snail’s slime and repels them with a small electric shock. Use a copper screen, flashing, or strips around the plant or the garden perimeter. Keep the surface of the copper clean for the best reactions. These bands are available commercially for use around the base of pots or around the base of single-stem plants. They are sold under a variety of commercial names but are generally known as “slug rings.”
This natural essential oil acts as a fungicide and insecticide to control aphids, Fusarium, gray mold, powdery mildew, Pythium, Septoria, spider mites, thrips and whiteflies. It can be purchased in a commercial blend with canola oil and a pH buffer as SM-90®.
Copper has numerous applications for agriculture, but its most common use for cannabis is the creation of a Bordeaux Mixture, which is comprised of equal parts copper sulfate and calcium oxide from slaked lime and used as a fungicide.
When cotton is processed the seeds are separated from the fiber and used to produce cottonseed oil, which entails mechanically separating the seeds from their hulls and extracting the oil using solvents or pressing. The kernel meat remaining after extraction is called cottonseed meal and it can be used as an organic fertilizer. The exact levels will vary somewhat, but the N-P-K ratio of cottonseed meal is roughly 7–3-2.
This category doesn’t refer to social customs but rather to ways of cultivating plants that help minimize or eliminate pests. For example, allowing the soil around plants to dry somewhat between waterings helps to control many sorts of soil-borne fungi and also reduces the population of fungus gnats. Watering in the mornings allows the soil to dry out before slugs and snails come out at night.
Growing in containers with pasteurized planting mix (either indoors or out) reduces or eliminates many soil-dwelling fungi and pests.
In outdoor gardens, maintain a favorable environment for beneficial insects and they’ll do a lot of your pest control for you. Indoors, keep grow room humidity under 50% to help prevent gray mold.
Keep light out of hydroponic water systems to prevent growth of algae. Keep your grow room clean and never bring in clothing that has just been outdoors—this helps keep out many pests.
Cultural controls are a key feature of IPM and encompass all the non-chemical crop management practices used to control pests and other plant ailments. Crop rotation, companion planting, thorough sanitation of the grow and surrounding areas are examples.
This material is available at most grocery stores. In addition to its many cooking uses, it repels ants. To apply cream of tartar, first determine where the ants are entering. This usually means following an ant trail back to a crack or other small opening in a wall, baseboard or window. Once the point of entry is found, sprinkle a liberal coating of cream of tartar on and around the opening.
For molds and fungi, ants, aphids, fungus gnats, mites, root aphids, scales, thrips, and whiteflies
D-limonene is an essential oil from the rinds of citrus fruits including oranges, lemons, and limes. It smells like citrus. It is the active ingredient in citrus-scented cleaning products. D-limonene’s mode of action is similar to pyrethrum. It both repels and paralyzes insects. It is available in a variety of formulations to kill and repel ants, hornets, wasps, fleas, and other insects. It is harmful to beneficial insects if sprayed directly on them. It also controls molds and fungi including Pythium, Fusarium and Rhizoctonia. Commercial products include Ortho Home Defense Indoor Insect Killer, Clean Green All Purpose Cleaner, TKO, D’Bug Safer Brand Ant and Roach Killer, Surefire Crawling Insect Killer, and Orange Guard Fire Ant Control.
Diatoms are microscopic sea creatures with hard silica shells. The diatoms of ancient seas left large deposits of a chalky mineral that can be easily crumbled into a white powder: diatomaceous earth. This is available at most garden supply shops. Their fossilized remains are a brittle, white talc-like powder that can be used as either a soil conditioner or a pesticide. It is harmless to humans and is often found in grain, which it is stored with to prevent pests.
Diatomaceous earth contains microscopic fragments of glassy silica that injure and even kill small, soft-bodied animals. Kill fungus gnat larvae and thrips pupae by placing a layer about 1 inch (2.5 cm) deep atop the soil in plant pots. Deter ants, slugs and snails with a thin but unbroken barrier of diatomaceous earth about 3 inches (7 to 8 cm) wide. Mix with boric acid, ground cinnamon or ground cloves to increase its effectiveness. It becomes ineffective when it is wet because the spikes soften.
Basic garden fertilizers are rated by their NPK numbers. These are noted on the label as a series of three numbers such as 15–5-10, 5–1-1, etc., describing the content of the three major macronutrients in the product. The first number always represents the nitrogen (N) content of the fertilizer. The number is the percent of the element in the fertilizer. The second represents the equivalent of the phosphorous compound P2O5. The third is the equivalent of the potassium (K) compound K2O (potash). Thus, a fertilizer with NPK values of 10–5-1 would contain 10% nitrogen, 5% equivalent of P2O5 phosphate and 1% equivalent of the potassium compound potash. For brevity’s sake, they are called N-P-K.
Choose a fertilizer according to the deficiency (if any) that you are trying to treat, and also to the growth stage of the plants. Nitrogen promotes vegetative growth, so it is most needed during the vegetative period. Avoid fertilizers high in nitrogen during the flowering stage. Conversely, phosphorous is most needed during flowering and should be used with care during vegetative growth. Potassium is useful at all stages of a plant’s growth and is added to balance the pH of high-phosphorous fertilizers.
Proper plant nutrition is crucial to maintaining general health. Make sure you factor in the N-P-K ratio of any potential fertilizer or additive and keep an eye out for impacts on pH balance.
Whole fish deemed unsuitable for regular food use (such as menhaden), and the bones and offal from processed fish, are pressed to remove the fish oil. The remains after this pressing are a brown powder (fish meal) and a liquid emulsion (fish emulsion). Both are high in nitrogen and useful organic fertilizers (especially for treating nitrogen deficiencies). They also provide many micronutrients that help prevent deficiencies.
Fish emulsion releases nitrogen to the plant more rapidly, whereas fish meal provides a steady, slow release. Look for brands such as Alaska Fish Emulsion, Fertrell Liquid Fish Emulsion, Down To Earth Fish Meal and Peaceful Valley Fish Meal.
Sometimes the only way to eliminate gophers and moles is by gassing them. Several “smoke bombs” are sold for this purpose, such as Dexol Gopher Gasser and Revenge Rodent Smoke Bomb. These are thick paper cartridges filled with charcoal, sodium nitrate and sometimes sulfur. You light the fuse and put it in the gopher’s burrow. Toxic fumes from the burning cartridge do the rest.
Fumigation usually involves the use of toxic chemicals, but organic fumigation is possible using carbon dioxide. This is often done in sealed environments, like grain or fruit silos, because it leaves no toxic residue on or in the food. However, it can be difficult and dangerous to maintain the required CO2 levels long enough to kill both the insects and their offspring.
Garlic is antifungal and antibacterial. It is used as an ingredient in fungicides and can be prepared as a spray and used every few days. Garlic has several pathways for destroying fungi, including its high sulfur content. Garlic can also be added to other antifungal sprays.
You can make your own garlic spray from a teaspoon of garlic oil in a pint of water with 2 ounces (60 mL) of 100 proof or higher drinking alcohol such as rum or vodka. Use garlic as a preventive. Spray on new growth before there is a sign of infection.
Apply about every 10 days. The odor lingers so it should not be used for two weeks before harvesting. Garlic spray is rinsed from the leaves by rain so it should be reapplied when the storm has passed.
Garlic is a general-purpose insecticide as well as fungicide, so it should be used with caution on outdoor plants. Garlic insecticides kill beneficial insects as well as plant pests like ants, aphids, caterpillars, spider mites, thrips and whiteflies. Brands include Dr. Earth Pro-ActiveTM Fruit and Vegetable Insect Spray, VeggiePharm®, Garlic Barrier®, BioRepel® and Envirepel®.
Garlic is also an ingredient in several commercial deer repellents, such as Deer-Off® and DeerPharm®.
Gliocladium is a genus of soil-dwelling fungi that attack and destroy pathogenic fungi such as Fusarium and Pythium. It is best applied as a soil drench before any symptoms of infection are noticed. Gliocladium fungicides are sold under brands such as Glio-mix®, SoilGard®, Primastop® and Prestop®.
Grapefruit seed extract is sold as a general-purpose disinfectant and can be used to control algae in hydroponic systems. Look for brands such as Citricidal® and Nutribiotic®. Follow label instructions for control of algae, as different brands contain different concentrations of grapefruit seed extract.
The powdered rock left over from quarrying granite (called rock dust, granite dust or stone meal) is a good slow-release source of potassium in soil and container gardening. Depending on the source of the stone, granite dust may also contain a variety of micronutrients, which are listed on the label. It is available through garden shops under brand names including Fishers Creek, Down To Earth and Agrowinn.
Granite dust is made by pulverizing naturally occurring granite stones. The resulting powder is an excellent soil amendment that will provide a steady source of minerals like calcium and will also supplement iron and manganese.
Greensand is not really sand but rather a soft, easily crumbled form of sandstone rock that is usually colored dark green. The green color comes from an iron-potassium silicate mineral called glauconite. As you might expect, greensand is a good slow-release source of potassium and iron when you don’t want to introduce nitrogen as well. Greensand is also a significant source of phosphorous and contains small amounts of many other micronutrients such as copper and manganese. Brands include Fertrell® Jersey Greensand, Gardener’s Supply Company Greensand and various local and store brands.
A naturally occurring sandstone, Greensand contains high levels of iron and potassium because of the presence of glauconite. It is an excellent soil amendment for organic gardening because of its mineral properties, as well as its ability to absorb water in soils with high levels of clay and retain it in sandy soils.
The droppings (guano) of bats and seabirds are harvested commercially and sold as organic fertilizers. Depending on the source, guano is high in nitrogen, phosphorous or both, and is an excellent relatively available fertilizer for treating or preventing deficiencies in these nutrients. Because guano varies widely, always check the NPK value on the label to make sure that a given guano fertilizer meets your needs. Guano is available under many different brands through garden supply shops.
To make the nutrients in guano more readily available to the plants, simmer the guano in water in a slow cooker outside, to avoid a major odor problem. Most of the nutrients will dissolve into the water and will then be available for immediate uptake by the plants. If you are making a large quantity, you may wish to prepare a concentrate to be diluted later. Keep refrigerated. The solution can be used either as a foliar spray or for irrigation.
Gypsum is a natural mineral composed of calcium sulfate (CaSO4). It is useful as a slow-release form of calcium or sulfur that doesn’t affect the soil pH too much. It should not be added to soils with a pH below 5.5 because it interacts with aluminum (Al) in those acidic soils, making the Al soluble and poisonous to the plants. Gypsum is available at garden centers under various local and store brands.
Gypsum can also be used to break up clay soils and is a naturally occurring mineral which, like lime, is high in calcium and can be used to address deficiencies.
Ants, aphids, caterpillars, fungus gnats, gray mold, mealybugs, powdery mildew, scales, spider mites, thrips, and whiteflies
Herbal oils are made from a range of plants, including cinnamon, citronella, clove, coriander, eucalyptus, lavender, lemongrass, mint, oregano, rosemary, and thyme. They can be used close to harvest because they evaporate in five to 10 days and do not leave a residue. These oils are some of Mother Nature’s repellents, and contact insecticides and fungicides that deteriorate the bodies of insects and mites as well as kill molds and fungi. When developing my herbal oil products, oils from plants that were not bothered by mites, ants, aphids, and powdery mildew were selected. By blending together several oils, there is a multi-prong attack: Some oils deteriorate the exoskeleton of the pest, while others destroy the internal tissue, and others the nervous system. Multiple applications of herbal oils break up the life cycle of the pest.
For spider mites spraying three times, three to four days apart, will eliminate them by knocking out hatchlings. Mist plants late in the day or late in the light cycle for indoor gardens. Always spray directly on pests that often reside on the underside of leaves. Store herbal oils in a cool, dark place with the cap firmly sealed. Availability of commercial pesticides and fungicides based on herbal oils has increased. Ed Rosenthal’s Zero Tolerance will eliminate mites as well as a wide range of soft-bodied insects and mold diseases Dr. DoRight’s blends oils as a defense against powdery mildew. Miticides include SNS-217 Spider Mite Control and Rasta Bob’s Death Mite. If the pests are in the soil, use a soil drench product like SNS-203.
Horticultural oils are any of a number of light oils used to control insects such as aphids, fungus gnats, leaf miners, mealybugs, scales, spider mites, thrips and whiteflies. They work by smothering insects, and so they must be applied directly to the target pests. They provide no residual activity. Some horticultural oils are vegetable-based, while others are petroleum-based. Both are effective, but if you wish to avoid petroleum products, be sure to check the label. In any case, petroleum-based oils should not be used on buds, or on leaves that you plan to use for cooking, collecting kief, or making extracts.
These oils need to be distinguished from neem oil, which poisons pests, although, like neem oil, some horticultural oils such as cottonseed oil, jojoba and sesame have fungicidal properties. They can be used in combination with other spray ingredients listed here. The oils are mixed at about 1–2% concentrations. A 1% solution is about 1 teaspoon per pint (5 mL per 500 mL), 3 tablespoons per gallon (40 mL per 4 L) and 1 quart in 25 gallons. Add a wetting agent or castile soap to help the ingredients mix.
Oil sprays should be used only on the leaves, not the buds. Use weekly on new growth. Horticultural oils are classified as “dormant” oils, which are used on plants during the winter season, and “summer” oils, which are used on growing plants. Summer oils tend to be lighter and more highly refined. Some oils can be used for either purpose. Marijuana gardens need only summer oils, and dormant oils can harm growing plants. So check the label on any horticultural oil you’re thinking of using in your garden to verify that it is rated for use on growing plants. Some suitable brands include Dr. Earth Pro-ActiveTM Fruit and Vegetable Insect Spray, GC-Mite®, OrganocideTM, Control Solutions Ultra Fine Oil and Green Light Horticultural Oil.
Hydrogen peroxide HP, chemical formula H2O2) is a contact disinfectant that leaves no residue. Use it to control algae, gray mold, Pythium and powdery mildew, fungus gnats and spider mites.. Hp can be used daily with no adverse effects on the plants: it produces only oxygen and water vapor as it works.
Household hp sold in drugstores has a concentration of 3%. Garden shops sell 10% hp. ZeroTol® contains 27% hydrogen dioxide and 5% peroxyacetic acid, with an activity equivalent to about 40% hp. It is considered hazardous because it can cause skin burn similar to that caused by concentrated acids.
HP is a great prophylactic treatment because it kills any spores and organisms with which it comes in contact, whether on table and wall surfaces, or on the plants themselves. It is used to sterilize equipment and spaces and can be used in combination with other treatments.
To treat plants with drugstore grade 3% hp, use 4 1/2 tablespoons (70 mL) and fill to make a pint (500 mL) of solution, or a quart of hp to 3 quarts of water.
With horticultural grade 10% hp, use about 4 teaspoons per pint (20 mL per 500 mL) and 10 ounces per gallon (300 mL per 4 liters).
With ZeroTol use about 2 teaspoons per pint (10 mL per 500 mL) and 5 tablespoons per gallon (75 mL per 4 liters).
Hydroponic supply companies stock a variety of products that are intended to supply the many micronutrients (as opposed to nitrogen, phosphorous and potassium, the macronutrients) that plants need. They are useful for treating or preventing various micronutrient deficiencies, including copper, molybdenum and iron deficiencies. Brands include BetterGrowHydro Micro-Mix, General Hydroponics FloraMicro and Bio-Genesis® Mineral Matrix Micro-Nutrient Supplement.
Note that some micronutrient products contain macronutrient fertilizers as well. There’s nothing inherently wrong with that, as long as you use a product that is balanced to provide the appropriate levels of nitrogen, phosphorous and potassium for the plants’ current stage of growth. Likewise, if you’re trying to treat a specific micronutrient deficiency, you’ll want to be sure that the product you’re using contains that nutrient. Always check the labels on nutrient products to make sure you know what you’re getting.
Iron phosphate is one of the best organic means of eliminating slugs and snails. Once they eat a small amount of iron phosphate, the pests stop feeding and soon die. It is harmless to plants and pets, unlike poisons such as metaldehyde. Iron phosphate comes in small white pellets. Sprinkle it liberally in a perimeter pattern around your garden, as well as in shrubbery, ground cover and other places where slugs and snails like to hide during the day. Sprinkle it over larger areas and across snail/slug paths. It is safe for humans and pets. Brands include Sluggo® and Escar-go®.
Use these products to correct iron deficiencies. Most contain chelated iron, iron sulfate or iron oxides. Brands include Glorious GardensTM Iron Sulfate, Bonide® Iron Sulfate, Monterey Dr. Iron, Phyto-Plus® Iron 5% and Biomin® Iron.
Kelp is a family of seaweeds. Certain types can be harvested and prepared as liquid or granular plant supplements. These concentrates contain a wide range of vitamins, minerals and macro- and micronutrients. They are especially useful for treating potassium and copper deficiencies. Brands include Kelp Help Liquid Kelp Concentrate, Gardens Alive® Liquid Kelp Spray, Bonide® Organic SeaGreen® Kelp Extract Concentrate and Tidal Organics Kelp Meal.
The green lacewing is a very useful beneficial insect. It takes its name from the adult stage, which looks like a small, green fly with fine lacy wings. The larval stage looks something like a grub or caterpillar, with an alligator-like mouth that makes it easy to distinguish from plant eaters. Both the adult and larval stages are ferocious predators of aphids, small caterpillars, whiteflies and any other small insects they can catch.
Photo by Brian Valentine
The main drawback to lacewings is that you can’t use them with other beneficial insects: the lacewings and their larvae are such fierce predators that they will eat other beneficials, or even each other if food is scarce.
Use lacewings in greenhouses and outdoor gardens but not in grow rooms. Outdoors, the adults will tend to fly away once they emerge from the larval stage.
Main species of interest are Chrysopa rufilabris and Chrysopa carnea. Buy them as either larvae or eggs from companies such as Bio Ag, Gardens Alive, Rincon-Vitova, Planet Natural, Natural Insect Control and American Insectaries. Plan on using about 1,000 eggs or 200 larvae for every 100 square feet (9 square meters).
As cute as lady beetles may be, both the adults and larvae are voracious pest predators. Like lacewings, lady beetles are also best suited to greenhouse and outdoor gardens. They tend to make suicide dives at the hot lights, so you’ll end up with dead insects all over your grow space. Though if you buy them as adults, they’re even more likely to fly away outdoors.
Photo by Mark Plonsky
Choose the species depending on your pest. Hippodamia convergens attacks aphids, while Cryptolaemus montrouzieri and Ryzobius lophanthae devour mealybugs and scale. Buy them as adults or larvae from companies such as Bio Ag, Gardens Alive, Rincon-Vitova, Planet Natural, The Ladybug Company, Ladybug Farms and EcoSolutions. Plan on using about 150 adults or larvae for every 100 square feet (9 square meters).
H. convergens, the common Lady beetle, lays eggs are cream or yellow in color and about one millimeter long. The eggs are laid in clusters on leaves, near prey. The number of eggs laid and their fertility depends on food abundance, ranging from 20 to 1000. When they hatch, the newborns are less than 1 millimeter in length. They immediately search for food. The mothers lay infertile eggs for the hatchlings to eat as their first food. The larvae look a lot like crocodiles. They molt three times into four instars, growing to 1 centimeter in a month. Then they spin a cocoon attached to a leaf and pupate for three days to two weeks depending on species and temperature. The pupae are often brightly colored yellow and orange. Newly emerged adults look for food and sex.
Lime is a general term for several calcium or calcium-magnesium compounds. All are highly alkaline and can be used to adjust soil pH upward or to correct calcium and magnesium deficiencies. All of these release calcium/magnesium slowly into the soil.
Calcitic lime will provide only calcium, but the use of dolomitic lime will also provide a magnesium boost. Lime also helps remediate acidic soil by introducing carbonates.
All forms of lime suitable for gardening can be found in large garden centers and through online garden supply shops. These different varieties of lime include:
Magnesium sulfate (MgSO4) is one of the fastest methods of correcting magnesium and sulfur deficiencies. Apply a solution of 1 teaspoon of Epsom salts per gallon of water (5 mL per 4 liters) in hydroponic reservoirs or as a foliar spray to treat deficiencies and in planting mixes. After the first treatment, treat with one-quarter dose with each watering or change of reservoir. It is sold in most large drugstores as Epsom salts.
Many pests can be effectively controlled by physically removing and destroying them. Often these methods can prevent or eliminate minor infestations, and they supplement other controls in more severe infestations. Some of the more common methods include:
Air filtration: Fungal spores and small insect pests such as aphids, spider mites and whiteflies can enter a grow space through the air intake. A fine dust filter keeps these pests out.
Boiling water: Pour boiling water into anthills to destroy these pests. Do not use this method within about 3 feet (1 m) of the plants, however, as it may damage their roots. Add ground cinnamon or clove to improve efficacy.
Bug zappers: Flying insects such as egg-laying moths are attracted to the blue light and electrocuted on the charged grid.
Handpicking and Shaking: Slugs, snails, caterpillars and similar large pests can be picked off the plants by hand whenever they’re spotted. Crush them or drop them in a bucket of soapy water to drown them. Look for snails and slugs in the early morning hours, as they hide from light during the day. Shake them off the plants.
Physical barriers: Water moats prevent ants from crossing. For example, put plant containers on blocks in a wide pan and fill the pan with water. Use old vegetable cans as cutworm barriers at the bases of plants. Wrap plants in steel wool to discourage rats. Use copper tape or wire to keep out slugs and snails.
Vacuuming: An ordinary vacuum cleaner can help control ants, aphids, caterpillars, spider mites (and their webs) and whiteflies. Use the vacuum hose and brush attachment, or a handheld vacuum cleaner such as a Dustbuster, to suck them out of the plants. Don’t get the hose close enough to suck leaves or buds in, as this may damage them.
Water spray: Remove and drown aphids, mites, ants and caterpillars by knocking them off the plants with a strong stream of water from a hose.
Wiping: Remove mealybugs and scale using a cotton swab moistened with rubbing alcohol.
Milk kills powdery mildew so well that rose growers all over the world have adopted it for their fungicidal sprays. It is used by home gardeners and commercial growers for many other crops as well. Use 1 part milk to 9 parts water. I’ve used only 1% milk, but some recipes call for either whole or skim milk and use up to 1 part in 5 milk. Some recipes add garlic or cinnamon to the mix. When using more than 30% milk, a benign mold is reported to grow on top of the leaves. This mold is harmless to the plant but not good for smokers, so if you notice such growth after using a milk spray, just reduce the concentration of milk in subsequent sprays.
To enhance effectiveness add 1 teaspoon potassium bicarbonate to the mix.
Use a milk spray at the first sign of infection. Then protect the new growth weekly.
The minute pirate bug (Orius sp.) is small, only 1/8 to 1/10 of an inch (1.5 millimeters) long, so it picks appropriately sized victims. Thrips and spider mites are its preferred food, but it also enjoys sucking the sweet flesh of small aphids, insect eggs, an occasional caterpillar, or anything else it can catch. Once the thrips population is under control, pirate bugs survive on aphids, mites, scales, whiteflies, and other biological controls, and each other. The minute pirate bug is a true bug: Its mouth is modified into a sharp hollow beak through which it slurps its dinner. The bug catches its prey, holds it with its two front legs, and uses its beak to pierce the exoskeleton. Then it sucks the victim’s flesh through its built-in straw Buy them as adults from companies such as Planet Natural, Rincon-Vitova, Bioplanet and Natural Insect Control. Plan on using about 50 adults for every 100 square feet (9 square meters).
Photo by Tom Murray
Mycorrhizae literally means “fungus-roots” and defines the beneficial symbiotic relationship between specialized soil fungi (Mycorrhizal fungi) and plant roots. A garden of microbes grows along a plant’s root surfaces. Mycorrhizal fungi extract nutrients and transport them to the root. There are two types of these beneficial soil fungi: endomycorrhizae actually penetrate the plant’s root cells, while ectomycorrhiza form sheaths at the root tip.
Mycorrhizal inoculants are best applied at the beginning of the season. The goal is to establish and maintain a healthy colony. Once established, the colony should be self-perpetuation
Plants with mycorrhizal roots are better fed, more drought resistant, and have a higher resistance to pathogenic infections. Another benefit provided is the filling of their environmental niche in the ecosystem, taking resources that otherwise may be available to pathogenic fungi. The fungi attach to the plant’s roots, feeding on the plant’s carbohydrates. In return, the fungi supply the plant with moisture, nitrogen, phosphorus, copper, calcium, magnesium, zinc, and iron, which the fungus collects and makes available to the plant.
Custom-blended mycorrhizal mixes can be added to your soil to encourage healthy root growth. Mycorrhizal products include MycoApply®, RootersTM Mycorrhizae Super Pack, Plant SuccessTM, MycoGrowTM and SoilMoistTM, among others. Benefits include:
Products available are:
Neem oil is pressed from the seed of the neem tree (Azadirachta indica), native to Southeast Asia but now cultivated worldwide. It is an effective killer of ants, aphids, fungus gnats, gray mold, leaf miners, mealybugs, powdery mildew, scale, Septoria, thrips and whiteflies. The crude oil has both insecticidal and fungicidal properties and contains at least 70 components. One group of these is the azadirachtins, which are said to account for 90% of the oil’s insecticidal activity. Other compounds including meliantriol, nimbin, nimbidin and salannin also have fungicidal qualities. Neem oil has low mammalian toxicity. In fact it is sometimes used as a toothpaste ingredient in India, and neem twigs are chewed and used as toothbrushes. It degrades rapidly once it is applied so it is safe for the environment, including nontarget species and beneficial insects.
Neem oil protects plants from fungus in several ways. First, it has fungicidal properties on contact as it disrupts the organism’s metabolism. Second, it forms a barrier between the plant and the invading fungus. Third, it inhibits spore germination. It has translinear action, that is, it is absorbed by the leaf and moves around using the leaf’s circulatory system. It can also be used as a systemic. Neem oil products are effective as foliar sprays and may also be added to soil or grow media in the irrigation water (1 teaspoon neem oil per quart, or 5 mL per liter). When applied in this way, neem products are taken up by the plant’s roots and distributed throughout the plant. As a foliar spray, neem oil should be diluted with water and a dash of wetting agent to a 1–2% solution. This solution should be used within eight hours. The fungicidal and insecticidal effects are more potent when applied by spray, but the systemic neem lasts longer. For fungicidal applications, neem oil is best used before the plant or the garden exhibits a major infection. Used in this way, it prevents the spores from germinating.
A few brands use cold-pressed or steam-pressed extract of the neem seed. These contain all of the oils found in the seed. Brands include Dyna-Gro, Monterey, Southern Organix, and United Industries.
Azadirachtin and some other components can be removed from the oil with alcohol. The oil that remains after this treatment is called Clarified Hydrophobic Extract of Neem Oil. This gives three main classes of neem garden products:
Water soluble neem products are also available. Neem cake remains after all of the oil has been extracted from the seed. It still contains insecticidal, nematicidal, and fungicidal properties, and high percentages of N-P-K and micronutrients. In India it is used as a fertilizer. It is applied at the rate of about an ounce per square foot, applied either as a mulch or mixed into the soil
Neem oil should not be applied for three weeks before harvesting.
States have various rules regarding use of neem and its derivatives. Make sure to use only approved formulations.
Nitrate (NO3) is the form of nitrogen most readily available to plants. Many nitrate salts, such as calcium nitrate (Ca[NO3]2) and potassium nitrate (KNO3), provide a quick shot of soluble nitrogen for treating nitrogen deficiencies. Brands include Champion, SQM Hydroponica and Ultrasol.
Several different species of wasp act as parasites on garden pests. These wasps are nonsocial, stingless to humans and so tiny that once you release them you may never see them again. The entire life cycle of parasitoid wasps revolves around the host pests. They lay their eggs in eggs, larvae or adult pests (depending on species), and the larval wasp then consumes the pest from within. Adult wasps often eat pests as well, depending on the species.
Photo by Brian Valentine
Choose the species depending on your pest:
The most successful biocontrol organism for the control of whiteflies in greenhouses is a tiny golden parasitic wasp called Encarsia formosa. Its preferred host is the greenhouse whitefly. A particular race, Nile Delta, attacks all major whitefly species so identifying the whitefly strain is not necessary. Adult wasps use sight and smell to find whiteflies. They lay eggs inside the whitefly larvae, preferably during their second instar. Whitefly larvae turn black as the wasp develops inside the body. After 15 to 25 days, the adult wasps emerge. It is most effective against the greenhouse whitefly and not as effective against the silverleaf or sweet potato whitefly. Three other parasitic wasp species, Encarsia luteola, Eretmocerus californicus, and Eretmocerus eremicus are commercially available for control of these species.
Buy them as pupae from companies such as Buglogical, Hydro-Gardens, IPM Labs, Natural Insect Control, Planet Natural and Rincon-Vitova. Plan on using about 100 pupae for every 100 square feet (9 square meters). Some pests may require multiple applications for full control.
pH-Up and pH-Down are generic terms for alkaline and acid pH adjustors, respectively. They are used to adjust water pH in indoor gardens and may come as either a powder or liquid. The active ingredient is usually potassium hydroxide (KOH) or potash (K2CO3) in pH-Up, or phosphoric acid (H3PO4) in pH-Down. Brands include General Hydroponics, GroWell, Growth Technology and many others.
Most fungi can grow only within a certain pH range. An alkaline solution with a pH of 8 makes the environment inhospitable for the fungus and stops its growth. Making up such a solution with pH-Down and applying it as a foliar spray is one of the simplest means of controlling foliar fungi such as gray mold and powdery mildew. It can be used on critically infected plants.
Many cannabis ailments are caused or exacerbated by improper pH and some pests are sensitive to the pH balance of a host as well, making regular monitoring and maintenance of your growing medium’s pH a crucial control.
Potassium bicarbonate (KHCO3) is used in the food industry but is also useful as a fungicide against Fusarium, gray mold, powdery mildew and Septoria leaf spot. It is a wettable powder that raises the pH of the environment surrounding the fungi. Potassium bicarbonate is better than sodium bicarbonate (baking soda) because potassium is one of the macronutrients used by plants. It can be used to cure bad infections and weekly to prevent new ones. Potassium bicarbonate is also useful against potassium deficiencies.
Studies show that potassium bicarbonate is more effective as a fungicide when used with an oil and a wetting agent. Use 1 teaspoon (5 mL) of potassium bicarbonate, a teaspoon of oil and a small amount of wetting agent in a pint (500 mL) of water, or 3 tablespoons (45 mL) each potassium bicarbonate and oil and wetting agent as directed in a gallon (3.8 liters) of water. It is also available commercially in Ed Rosenthal’s Zero Tolerance® fungicide, Armicarb100®, Kaligreen®, FirstStep®, Remedy®, Milstop® and other brands. Spray weekly as needed.
Potassium sulfate (K2SO4), potassium silicate (K2SiO3) and potassium phosphate (K3PO4) are highly soluble salts that can be used to supplement a plant’s potassium needs without introducing nitrogen (or phosphorous, in the case of the sulfate and silicate). Potassium sulfate is also sometimes called SOP (sulfate of potash). Brands include Champion, Pro-Tekt, Hydro-Gardens, Planet Natural and AllganicTM Potassium.
Deer avoid areas that smell of predators such as coyotes. Repellents based on predator urine exploit this behavior. Dog urine and even human urine can also be used, especially if the humans are meat eaters. Stale, strong urine is most effective.
Rather than applying these repellents directly to marijuana plants, create a barrier by applying them to other plants that grow around your garden. Another method is to string a rope or cord around the garden and tie cloth strips to the cord every 3 feet. Apply the repellent to the cloth strips to deter deer. Look for these repellents under brands such as CoyotePee® and Deer Busters® Coyote Urine.
Set a mite to catch a mite. Predatory mites breed rapidly (especially indoors) and eat fungus gnats, spider mites and thrips. Look for species such as Amblyseius, Galendromus, Hypoaspis, Neoseiulus and Phytoseiulus.
Plan on using about 30 to 50 adults per plant, or 300 per 100 square feet (9 square meters). Note that while predator mites do reproduce quickly, they can’t play catch-up with a rampant spider mite infestation. If your infestation is already out of control, then use a non-persistent insecticide to reduce the spider mite population before releasing predator mites.
Buy predatory mites as adults from companies such as Buglogical, Planet Natural, Hydro-Gardens, Natural Insect Control, Peaceful Valley and EcoSolutions.
These are microscopic creatures that live in soil and attack pests that spend their larval stages in soil, such as thrips and fungus gnats. Look for species such as Steinernema and Heterorhabditis. They can live for months in soil, so they can be applied as a preventive as well as to control existing infestations.
Unlike many beneficials, predatory nematodes are bought in bulk either as spray solutions or in sponges that you soak in water, then apply the water as a spray or soil drench. There are name brands such as NemaShieldTM and Scanmask. Buy from companies such as Buglogical, Planet Natural, Worm’s Way, Hydro-Gardens, Natural Insect Control and Peaceful Valley. Coverage rates vary, so apply according to the manufacturer’s directions.
This is a bacterial genus that contains several fungicidal species. Note that different Pseudomonas species are effective against different pathogens, so check the label to make sure that the one you’re buying controls the diseases you’re targeting. Pseudomonas products such as BioReleaf®, Blight-Ban® and Bac-Pack® control fungi such as gray mold, Fusarium and Pythium.
In combination with garlic and capsaicin, rotten eggs are a potent deer repellent. Look for brands such as Deer-Off®. Apply as recommended by the manufacturer.
Pyrethrum is a broad-spectrum natural insecticide, derived from a plant in the chrysanthemum family. It acts on contact and so must be sprayed directly on the target pests. It is effective against ants, aphids, caterpillars, fungus gnats, leaf miners, mealybugs, scale, spider mites, thrips and whiteflies. Note that pyrethrum is also toxic to many beneficial insects, fish and reptiles.
Pyrethrum is an organic insecticide, but some formulations include a synergistic additive, piperonyl butoxide, a powerful enzyme that interferes with insects’ ability to filter out toxins.
Including it in the formula helps the pyrethrum stay in the insect’s body longer but it is not considered safe for use with cannabis.
Pyrethrum is the natural extraction, but there are also synthetic versions called pyrethroids.
Pyrethroids use the same pathways, are effective, and low in toxicity. Mammals’ metabolic processes quickly dismantle the pyrethroid’s toxic effects, although high doses given to rats have produced some damage. Pyrethroids are synthetic compounds and are not considered organic and are not permitted in some areas.
Pyrethrum and pyrethroids do not persist in the environment and are quickly broken down by UV light and high temperatures so they do not cause any long-term contamination of soil or surfaces.
Use pyrethrum by spraying it directly on pests. Pyrethrum works by interfering with arthropod nervous systems, disrupting the neurotransmitters. They are paralyzed and die.
Pyrethrum kills ants quickly, so the ant foragers often don’t have a chance to bring it back to the colony. This makes it less appropriate when the goal is to affect the total nest population.
Pyrethrum teas poured into colonies or mounds are fairly successful clearing out ants that are immediate problems. Use the pesticide as a drench to kill insect larvae in the soil. Follow manufacturer’s instructions but use half strength two times a few days.
Pyrethrum formulations range from powders to sprays and are available under many different brand names, including Safer Yard and Garden Insect Spray, Planet Natural® Pyrethrum Powder and PyGanic Crop Protection.
Most states permit pyrethrum, but not with additives, many of which may be outlawed.
This is a class of compounds that act as broad-spectrum disinfectants. They are effective against many algae and many fungal pathogens, including gray mold, Fusarium and Pythium. Use these products for general disinfection of tools and hard surfaces, but do not use them directly on or around edible (or smokeable) plants. Physan 20® and Prontech® are popular quaternary amine preparations for horticultural use.
Rock phosphate is a naturally occurring phosphate mineral. Used as a soil amendment, it releases phosphorous slowly and helps to prevent phosphorous deficiency. It is available in garden centers under brands such as Montana Natural, Peace of Mind and Espoma Organic Traditions.
Be careful to distinguish between rock phosphate and so-called superphosphate or triple phosphate. Rock phosphate is suitable for organic gardening, but the other two are prepared by treating rock phosphate with powerful acids to make a product that releases phosphorous much more quickly. Rock phosphate that has been processed in this way is no longer acceptable in organic gardens. It may release phosphorous too quickly for sustained vegetative growth.
Rosemary will protect against insects
Rotenone is one of the more toxic natural insecticides. It is a broad-spectrum insecticide that is also toxic to fish, small amphibians and even mammals, including humans. to a lesser degree. It acts by disrupting metabolism at the cellular level. Rotenone kills most chewing insects (including beneficials), but there are less-toxic alternatives.
Rotenone is banned from food crops, including cannabis, in some states, although it breaks down naturally in the environment over 7–10 days.
Rotenone is sometimes used as an adjuvant in combination with pyrethrum. Avoid products that contain rotenone Avoid products that contain rotenone.
This bacterium produces an insect toxin, spinosyns, which are a new class of organic insecticides, when it is cultured in a nutrient broth. They are effective against ants, caterpillars, leaf miners, spider mites, thrips, and other arthropods: In combination Spinosyn A and Spinosyn D., act by highly exciting the insects’ nervous system to the point of dysfunction. Mortality is assessed at 100 percent. This combination acts when ingested and on contact. It does not affect nontarget insects, such as beneficials. However, it is toxic to bees, so use outdoors with caution. It acts quickly; insects die within one to two days, but it must be eaten by them to be effective. It does not persist in the environment and breaks down into carbon, hydrogen, oxygen, and nitrogen when exposed to sunlight and microbes. It is marketed under the active ingredient name spinosad. Spinosad Brands include Monterey Garden Insect Spray, Captain Jack’s Deadbug Brew, Conserve SC, and Entrust.
The oil pressed from sesame seeds has both insecticidal and fungicidal properties. It is effective against aphids, fungus gnats, gray mold, leaf miners, mealybugs, powdery mildew, scales, Septoria, spider mites, thrips and whiteflies. Sesame seed oil has both fungicidal and insecticidal properties. Sesame oil smothers insects by clogging their spiracles, the breathing holes along their body, and creates an unfavorable environment for fungi to take hold. You can also make your own using sesame oil from a health food or gourmet shop. Mix it 1% (1 teaspoon per pint or 5 mL per 500mL) with water and a small amount of lecithin and a wetting agent. It is available under brand names such as Organocide® (a blend of sesame oil and fish oil) and Green Light® Bioganic® Home and Garden (a mixture of sesame, clove, thyme, soybean and wintergreen oils).
Silica is not known to be essential for plant growth. However, when it is available to them, plants absorb it through their roots. The plants park the silica in the cell wall as well as internally in the cell. They also use it to form protective sheaths near the leaf surface.
Farmers used to protect plants from fungal diseases using sprays made from extracts of plants with high silica content such as the horsetail plant (Equisetum arvense), which contains 15 to 40 percent natural silica. In controlled experiments, plants with high silica content were protected against powdery mildew. Silica is alkaline so one of its modes of action may be to create a no-grow environment for the fungus.
Plants grown with ample amounts of soluble silica grow thicker cell walls, which results in stronger stems. It helps resist fungal and insect attacks. It also positively affects the plants’ sensitivity to absorption and translocation of several macro- and micronutrients. It acts as a “toughening agent,” increasing the plant’s ability to survive stressful situations such as drought, high salinity and nutrient imbalance.
Hydroponically grown plants with soluble silicon added to the water solution had reduced incidence and severity of powdery mildew in several trials. They also had increased yields and produced thicker, whiter, healthier root systems. Foliar silicon sprays also protect against powdery mildew.
Sources of silica include:
Colloidal silver is a suspension of very fine silver particles. It has a long history as a general-purpose disinfectant, including use as an algaecide in pools and hydroponic systems. Used according to label directions, it will not harm marijuana plants. Several commercial brands are available, including Regal Pool Chemicals Silver Algaecide, Haviland Silver Algaecide and Silver Algaedyne®.
However, when sprayed on plants daily during early flowering it often causes hermaphroditism.
Insecticidal soaps are mild soap solutions that damage the exoskeletons of soft-bodied insects (such as aphids, mealybugs, scales, spider mites, thrips and whiteflies) and cause them to dehydrate. They work by direct contact and so must be sprayed directly on the target pest.
You can make your own pesticidal soap solutions by mixing a few drops of a mild soap (the author prefers Dr. Bronner’s Peppermint® castile soap) in a pint of water. However, some soaps can be toxic to plants, so always test a new soap by spraying it on a small area of one plant and waiting a day or two to check for damage. Commercial insecticidal soaps include Neudorff’s Insecticidal Soap, Concern Insect Killing Soap, Monterey Quick, Safer Insecticidal Soap and M-Pede®. Soaps are also sold as algaecides under brands such as Schultz Garden Safe® Moss and Algae Killer and DeMoss®.
Sodium bicarbonate (NaHCO3), baking soda, has the same mode of action as potassium bicarbonate and is effective against the same diseases. It is often used by gardeners instead of potassium bicarbonate because it is readily available in most kitchens. However, it is not as effective as potassium bicarbonate and leaves sodium in the soil when it breaks down. Although I haven’t heard of any cases where there was so much sodium buildup that it affected plant growth, it is prudent to use potassium bicarbonate.
For the purposes of cannabis cultivation it serves as a foliar treatment for powdery mildew that will change the pH of the leaf surface from roughly 7 to 8, making it inhospitably alkaline for most fungi including powdery mildew.
There is no problem with using baking soda at the first sight of powdery mildew. It works and has been used by finicky rose growers for more than 70 years. Use 1 teaspoon (5 mL) of potassium bicarbonate, a teaspoon of oil and a few drops of wetting agent or castile soap in a pint of water (500 mL), or 3 tablespoons (40 mL) each potassium bicarbonate and oil and a wetting agent or 1/2 teaspoon liquid castile soap in a gallon of water (3.8 L). Spray weekly.
Streptomyces Griseoviridis is an actinomycete, a member of a curious group of organisms that fall in between fungi and bacteria based on gross morphology, but are truly bacteria. It colonizes the surfaces of plant roots. It produces metabolites that inhibit the growth of Fusarium, Botrytis, Rhizoctonia, and Pythium, and enhances the host plant’s growth. S. griseoviridis prefers humid, soil, a wide range of soil pH levels, and temperature between 50°F and 68°F. It is also compatible with other growing additives, such as rooting hormones, and does not seem to affect other beneficial organisms. S. griseoviridis is available as spores and mycelial fragments in a powder. It grows a protective sheath around roots protecting them from attacks by pathogens. It also forms a bond with the roots that results in increased vigor and stress resistance. Use it to treat seeds, as a root dip, or soil drench. It is marketed as Mycostop.
For damping off, gray mold, powdery mildew, root rot, Verticillium wilt, and other pathogenic root fungi
Streptomyces lydicus is a naturally occurring common soil bacterium normally present in healthy “living” soil. When it is inoculated to improve poor soils and planting mixes, it provides protection against pathogenic fungi. It grows on the tips of plant roots, attacking pathogenic fungi. It can also be used as a foliar spray to treat powdery mildew and gray mold. S. lydicus grows well in normal garden temperatures and pH levels. The bacterium spreads along the plant’s roots as they grow into the rhizosphere, which is the area around the root. This shields plant roots from pathogens. The bacterium releases an enzyme which weakens the fungus’ cell wall as well as releases fungicides that inhibit the pathogen’s growth. Use in early growth so it establishes early. S. lydicus does hinder mycorrhizal fungi growth. Hydrate the powdered bacteria by mixing it into soil mix. To use as a drench or foliar spray, mix it in water. It is safe for use around insects, other animals, and people. In hydroponic or sterile systems, introducing S. lydicus restores its natural presence on plants. In soil systems, adding Streptomyces lydicus elevates colony levels for increased benefit. It is available under the brand name Actinovate.
These bacteria produce fungicidal agents effective against gray mold, Fusarium, and Pythium. Brands such as MycoStop®, RootGuard® and Microgrow® contain Streptomyces formulations. These products are usually applied as a soil drench before symptoms appear.
Sulfur has been used to control gray mold, powdery mildew and Septoria for centuries. Several foliar sprays containing sulfur are available, such as Thiocal® and Safer® Defender Fungicide, but they may cause leaf damage. Check such products on a few branches and wait a day or two to check for problems before applying to your entire garden. The preferred delivery method for most marijuana growers is vaporization. Sulfur vaporizers use powdered elemental sulfur (also called garden sulfur), such as Thiolux Jet or Yellowstone Brand Hi-Purity Prill, heated in a container above a 60-watt lightbulb. The vapors condense into a fine film of very low pH sulfur granules on the leaf surfaces. The low pH environment inhibits fungal growth. Sulfur candles are available at some garden centers and work in a similar way.
Note that sulfur vaporizers produce a strong smell of sulfur. Air out your grow space after using a sulfur vaporizer. Sulfur should not be used with oils or when the temperature is over 85°F (29°C).
Check state regulations to make sure that use of sulfur is legal in your state.
In addition to its fungicidal properties, garden sulfur is useful for lowering the pH of alkaline soils and for correcting sulfur deficiencies.
Trichoderma is a genus of parasitic predatory fungi that develops a symbiotic relationship with roots. By wrapping itself around the roots it presents a physical barrier to pathogens. The fungi provide the roots with needed nutrients and use the root’s exudates for nourishment. This increases plant resistance and vigor. The fungi also attack pathogens in the environment and use them for nourishment, too.
Several trichoderma species, such as T. harzianum, provide protection against fungal diseases including Fusarium, gray mold, Pythium, Septoria and Verticillium. PlantShield® and RootShield® use a particularly effective patented strain of T. harzianum: strain KRL-AG2, developed at Cornell University. Look for other brands also such as Trichodex®, Bio-Fungus® and BioTrek®. These products are applied as a soil drench for Fusarium, Pythium and Verticillium or as a foliar spray for gray mold and Septoria.
Urea is not an organic fertilizer, but it is one of the best relatively available nitrogen sources. Because urea is so high in nitrogen (NPK 45–0-0), follow the label directions carefully to avoid nutrient burn. Brands include Espoma Quick Solutions Urea and many local and store brands.
For bacteria, damping off, fungi, all molds, powdery mildew, and root rot. UVC light is considered deadly to life and kills the spores and tissues of powdery mildew, Pythium spp., Botrytis, and other fungal pathogens.
There are three ways that it is used.
First, there are water sterilizers that kill pathogens in the water supply. As the water passes around the UVC fixture, microorganisms receive fatal rays. The fixtures can also be used to clean inline water in recirculating hydroponic systems after filtration. Place the fixtures in the ventilation systems of growing rooms to kill fungi and bacteria spores before they enter the growing space. In closed areas use systems designed for sterilization in restaurants. The light is fatal to all airborne organisms passing through it. Some brands of lights are Big Blue, Turbo Twist, and Air Probe Sanitizer. Hand-held UVC wands and automated systems are used to prevent fungal infections. They kill powdery mildew spores on leaf surfaces. The light passes over each plant for only a second each day. This is enough to keep the plants fungus- free. Aeon UVC Systems is the only company manufacturing for the garden industry.
Vinegar is toxic to powdery mildew. Use it at the rate of 1 tablespoon per quart (15 mL per liter) of water. Some gardeners recommend alternating vinegar with potassium bicarbonate and milk.
Wasps in the Trichogramma genus are also known as chalcid wasps. These small parasitic members\ of the order Hymenoptera are effective against many species of Lepidoptera. They lay their own eggs inside moth or butterfly eggs, which hatch into larvae that feed off the contents of caterpillar eggs. The eggs hatch and go through growth and metamorphosis inside the Lepidoptera egg, emerging as adult wasps rather than caterpillars. They solve caterpillar problems without the introduction of any chemicals, natural or otherwise. As such, Trichogramma has become one of the most popular biocontrol measures by farmers and gardeners around the world. These wasps are so tiny, about 0.5 millimeter from one tip of the wing to the other, that you may not even see them. Adults have pear shaped wings with a single vein and fringed edges. The best use of Trichogramma is to release them when either moths or caterpillars are first sighted in the garden. Depending on the size and location, multiple weekly releases may be needed over a three to six week period. A good rule of thumb for each release is about one wasp per square foot.
Trichogramma are available commercially. Its pupae are glued to small paper or cardboard squares, which are placed in the garden. The wasps hatch and breed without any further effort on the part of the gardener.
This is a broad class of compounds that break the surface tension of water. This prevents water solutions from beading up on plant surfaces and helps them penetrate into soil. Castile soap (the author prefers Dr. Bronner’s Peppermint®) can be used as a wetting agent. Commercial brands for organic gardening include Coco-Wet, ThermXTM 70®, Phyto Plus® Foliar FriendTM, Natural Wet® and RainGrow SuperflowTM.
Zinc phosphide (Zn3P2) is an old rat poison now seeing a resurgence in popularity. It is fast-acting and more specific than some other poisons because it has a strong garlic odor that attracts rodents but repels most other animals. It is sold in baits under brands such as Nu-Kil®, ErazeTM Rodent Pellets, Prozap® Zinc Phosphide Oat Bait and ZP Rodent Bait AG. As with all rat poisons, zinc phosphide baits should be deployed in tamper-proof bait stations in accordance with the manufacturer’s instructions.
Zinc sulfate (ZnSO4) and zinc oxide (ZnO) provide supplemental zinc in cases of zinc deficiency. Brands include Spectrum Chemical, BLU-MIN® Liquid Zinc Sulfate and NutraSul Plus 18% Zinc-Sulfur Fertilizer. It is also available in combination with Fe and Mn.