BUILD HEALTHY SOIL by applying compost, mulch, and natural fertilizers. See Chapter 2 for details on soil building.Q What steps should I take to begin growing my vegetables organically?
A First, stop using chemical pesticides and fungicides. When you garden organically, you won’t ever use those products, and even approved “organic” pesticides will be your last resort. There are lots of effective pest-control methods that don’t involve spraying, but you can also try homemade sprays using such ingredients as baking soda and dishwashing liquid. These may solve all, or nearly all, your pest problems. More and more organic products are available at garden centers these days, so this switchover is a lot easier than it once was.
Keep in mind, though, that there also are homemade remedies that will eliminate problems, and there are effective preventive steps to take long before you bring out a sprayer. The following tips and techniques are a key part of avoiding pest and disease problems in an organic garden, but read on in this chapter for more options.
BUILD HEALTHY SOIL by applying compost, mulch, and natural fertilizers. See Chapter 2 for details on soil building.
ASK EXPERTS as well as friends and neighbors who garden which pests and diseases pose the biggest problems in your area. Find out how they control these problems organically.
WALK THROUGH YOUR GARDEN DAILY — or every other day at minimum — to check for pests as well as signs of diseases or other problems. Catching problems early allows you to step in and correct a problem before it becomes severe.
KEEP PLANTS WELL WATERED AND FERTILIZE REGULARLY if you suspect your soil is not yet up to par. Plants that are healthy and growing vigorously are far less subject to problems than ones that are struggling.
SEE ALSO: For homemade spray, page 145.
Q What are some easy organic controls that are good to use for most crops?
A The smart way to deal with pest problems is to avoid allowing pest or disease organisms to invade your crops in the first place. Here are some techniques to try:
PLANT RESISTANT AND TOLERANT CROPS. Crops with built-in resistance or tolerance to disease stack the deck in your favor. You’ll see these characteristics listed in descriptions on seed packets and catalogs.
INSPECT TRANSPLANTS CAREFULLY at the garden center. Don’t buy any that have insect infestations or obvious signs of disease. Stocky, healthy-looking plants are your best bet for producing bumper crops.
USE ROW COVERS. These prevent pests from ever reaching your crops so you don’t have to spray at all.
USE CUTWORM COLLARS WITH TRANSPLANTS. These prevent cutworms from cutting down transplants altogether.
PICK OFF AND DISPOSE OF DISEASED LEAVES during daily inspection tours. Signs of disease include spotting or yellowing.
ENCOURAGE BENEFICIAL INSECT by planting some annuals and perennials with daisylike flowers.
DON’T WORK IN THE GARDEN WHEN PLANT LEAVES ARE WET. Wet conditions make it easy for you to transport fungus spores and other disease-causing organisms from plant to plant on your hands and clothes.
HANDLE PLANTS CAREFULLY. Bruised leaves and torn stems give pests and diseases easy access to plants.
SEE ALSO: For information on how to use row covers, page 135; for details about cutworm collars, page 157; for suggestions for beneficial insects, pages 138–139.
Q As I walk around my garden every day, what should I look for specifically?
A During daily inspection tours, start by looking at your plants as a whole. Are they stunted, wilted, or deformed? Have seedlings fallen over or disappeared? Have branches died? Also look closely for such symptoms as webby stem tips, curled or blackened growth, and leaves that have spots or are distorted, sticky, curled, tunneled, or chewed. All are common pest or disease symptoms. Be sure to check out the undersides of leaves and inside flower blossoms, both of which are places pests commonly hide. Don’t forget to examine the soil around the plants, since pests such as cucumber beetles frequently hide there as well.
Aphids
Leafminer tunneling
SEE ALSO: To find out what’s causing the problem and how to handle it, pages 146–162.
Q If purchased sprays aren’t the only thing organic gardeners use to control pests, what other techniques are effective?
A There are several levels of acceptable organic controls, and purchased or homemade sprays usually are the last resort when dealing with an insect or disease problem.
CULTURAL CONTROLS are the first line of defense against pests and diseases. These include techniques like growing resistant or tolerant crops and keeping plants healthy and well watered. Cleaning up and discarding diseased plants is another cultural control that reduces the problems you’ll encounter in future years.
BIOLOGICAL CONTROLS are another type of very effective controls. Birds, along with beneficial insects that feast on pests, are two examples of biological controls. You also can purchase biological controls, including Bacillus thuringiensis (Bt), a popular microbial insecticide that infects and kills many types of caterpillars, beetles, and other pests. Spinosad is another, relatively new biological control that is effective against caterpillars, thrips, and a variety of other insects. It is also the active ingredient in new organic fire-ant baits.
PHYSICAL CONTROLS include floating row covers, cutworm collars, and other barriers that block insects from reaching plants or discourage them from feeding, such as kaolin clay (a natural mineral substance used in a wide variety of products, including toothpaste) and wood ashes. Blasting aphids and other small pests off plants with a stream of water also is an effective physical control. Handpicking, trapping, and pulling and destroying infested or infected plants or plant parts are other effective physical-control options.
The easiest way to handpick insects is to tap them into a bucket or large-mouthed jar of soapy water, where they’ll sink to the bottom and drown. For best results, do your handpicking in the early morning when insects are still a bit cold. They move more slowly then, making them easier to catch.
For fast-moving bugs, try a different strategy. It may come as something of a surprise, but a small, cordless, handheld vacuum cleaner is a great tool for sucking up speedy pests. Just suck them up, then dump them into a bucket of soapy water.
Q My neighbor covers some of the beds in his garden with what look like white sheets. He calls them floating row covers. What are they for?
A Floating row covers are sheets of lightweight, spun-bonded polyester or polypropylene that gardeners use to protect crops from pest damage as well as from cold injury. The covers are available in two different weights: lightweight for use as an insect barrier and heavyweight that provides frost protection to about 28°F/-2.2°C. (You can also double up lighter-weight covers to protect plants from the cold; each sheet provides 2 to 4 degrees of protection.) The fabric allows sun, water, and air to reach plants, but at the same time, floating row covers are one of the most effective tools for preventing damage from such leaf-chewing pests as flea beetles and caterpillars. They’re also handy for sheltering any type of vegetable crop if the weather gets a little too nippy. They provide protection from wind, thereby maintaining seedbed moisture and also helping prevent the soil from crusting, so seedlings can emerge more easily. You can buy row covers in various widths and lengths; one common size is 6' x 9'/1.8 x 2.7 m, which covers a 3'-4'/.9 to 1.2 m-wide bed, or you can buy rolls up to 50'/15.2 m long and cut them to fit as needed.
Q How do I install row covers, and what else do I need to know to use them?
A Installing row covers is easy: Simply lay the covers over the garden bed (do this on a windless day if possible). If you’re using only a single layer of lightweight row cover, you can lay it directly over the plants; for double layers or heavier-weight frost-protection covers, it’s a good idea to install hoops to keep the covers up off the plants. To prevent insects from crawling under the covers to reach your plants, bury the edges of the cover with a mound of soil all the way around the outside of the bed. Or use wire staples (sold for this purpose) to hold down the edges. For best results with staples, fold over the edge of the row cover and pierce both layers. Keep in mind that row covers prevent pollinating insects such as bees from reaching crops, so if you’re growing plants that aren’t self-pollinating, you’ll need to remove the row covers once flowers appear. Also, weeds thrive in the protected conditions under row covers, so you will have to take off the covers regularly to weed.
Soil secures row cover edges
Q Insects give me the creeps. I’d like to get rid of all the bugs in my garden, but I’ve heard that’s not a good idea. Why not?
A Lots of people share your dislike of creepy crawly things, but if you want a successful garden, it’s important to tolerate insects, even if you can’t learn to like them. Entomologists estimate that about 90 percent of insects are beneficial. The best-known beneficial insects are lady beetles, which feed on pests like aphids and spider mites, and honeybees, which pollinate crops and are essential if your melons are going to produce fruit without your intervention, for example.
Widespread spraying kills these beneficial insects right along with the pests. Insects that prey on caterpillars and grubs include yellow jackets, hornets, ground beetles, tachinid flies, and many true bugs. Dragonflies aren’t usually mistaken for garden pests, but here’s a good reason to encourage them to visit your yard: They eat mouthfuls of gnats and mosquitoes as they fly! So try to focus on the good things insects can do in your yard and garden, and design your garden to encourage them to stay around.
Don’t worry that insects will overtake your garden. The more types of insects you encourage in your garden, the better the chances that beneficial species will keep the pests in check. You’ll still want to monitor populations of pest insects in your garden by walking along the rows and looking for problems. Once you spot a problem — aphids or spider mites that have built up on a particular crop, for example — check to see if lady beetles or other beneficials are moving in to dispatch them. If not, take steps to correct the problem.
SEE ALSO: For more on defensive steps to take, pages 146–162.
One of the most effective controls for aphids and spider mites is to simply blast them off your plants with a hose. Pests like aphids appear first in the garden, but it takes populations of beneficial predators a bit longer to build up and take care of these pests. Blasting pests off plants with water may seem like a stopgap measure, but by the time the pests have regrouped, the predators will be in place and able to keep them under control.
Q How do I attract so-called beneficial insects to my garden?
A Try these tactics to encourage “beneficials” to make your garden their home:
ALLOW SOME WEEDS. Leave a weedy patch alongside your garden, or leave a few weeds along the rows. These provide shelter and an alternative food source for beneficials.
PLANT SOME FLOWERS. Including companion plants that provide nectar and pollen is a great way to encourage beneficial insects.
CONSIDER PERMANENT PATHWAYS. Beneficials can hide in mulched pathways or nearby mulched flower beds during times when you are harvesting or spraying in the vegetable garden.
MAKE A BUG BATH. Insects need water, too! Fill a shallow dish with stones and water to give beneficials a safe place to drink.
“Bug bath” for beneficial insects
BENEFICIAL INSECTS ATTACK PESTS in a variety of ways. Some adults attack and eat pests directly, while others simply lay their eggs on insect pests and let their larvae do the damage after they hatch.
Braconid wasps are one example of this latter lifecycle: The adult wasps feed on nectar, not insects. However, when it’s time for them to lay eggs, they’ll seek out tomato horn-worms for depositing their eggs. The braconid larvae feed on the hornworm, and then emerge and spin cocoons on the outside of the worm. If, during one of your garden-inspection tours, you see a large green caterpillar, usually on a tomato plant, covered with tiny white cocoons that look like grains of rice, don’t kill it! Move it off the tomato plant and then leave it be. From the little cocoons will emerge adult wasps that will attack other caterpillars.
Some gardeners practice a technique known as companion planting, and grow flowers not only to beautify their yards, but also to attract beneficial insects whose larvae attack pests. Aster-family plants (Asteraceae) like daisies, asters, and yarrows (Achillea spp.) are a rich source of nectar for adult braconid wasps and many other beneficial insects. Members of the mint family (Lamiaceae), such as mints (Mentha spp.) and catmints (Nepeta spp.), also are good choices, as are plants in the carrot family (Apiaceae), including dill (Anethum graveolens), fennel (Foeniculum vulgare), and parsley (Petroselinum crispum).
Q Is using a “bug zapper” a good way to keep insects under control in my garden?
A Actually, bug zappers (light traps that use an ultraviolet light) kill as many beneficial insects as they do pests, so they’re not a very effective way to control pests. If you’re growing sweet corn, though, a light trap located out in the corn patch helps control adults of corn ear-worms, European corn borers, and fall armyworms. To minimize damage to beneficials, put the light trap on a timer and run it between 11:00 P.M. and 3:00 A.M.
Q Are there any creatures besides beneficial insects that help control insect pests?
A Insect-eating birds are beneficial, and bats are tremendous insect consumers. A full-size toad can gobble about three thousand slugs and other insects a month, and frogs make good garden hunters as well. Even in suburban neighborhoods, a backyard water garden can attract or support frogs and toads. Be sure to soaking area incorporate a shallow soaking area, no more than a couple inches deep so toads have access to water. Soaking areas can be freestanding, away from a conventional pond. Just dig out a shallow depression, cover it with a piece of rubber pond liner, then hide the liner with a layer of rounded river rock. Your soaking area will provide a safe watering hole for birds, beneficials, and other wildlife, including toads. Be sure to flush it out with a hose and replace the water every few days. Other beneficial creatures to encourage are spiders and snakes.
River rocks cover pond liner
While crows have been known to walk along corn rows, pulling up seedlings and eating the seeds, for the most part birds are beneficial garden visitors. When they have babies to feed, bluebirds, wrens, and other songbirds consume a tremendous number of insects (admittedly, pest and beneficial alike). So make an effort to attract birds to your yard. Install a birdbath, and give it a weekly cleaning; use an electric de-icer to keep the water unfrozen all winter long. If you’ve had insect pest problems in a particular bed, you may want to leave that bed unmulched for a few weeks after harvest and lightly turn the soil to bring up larvae and pupae for the birds to eat. Plant native shrubs and trees to provide food and nesting sites. Since birds such as chickadees spend their time in winter feeding on aphid eggs and other “potential” insects, you may want to institute a program to encourage them to stay year-round.
Q What kinds of safe, organically acceptable insecticides do garden centers offer?
A Organically acceptable chemical controls are the last resort, the final line of defense for organic gardeners. These include soap sprays, along with stronger pesticides derived from plants or other naturally occurring substances. Look for products that say “organic” on the label. Neem, pyrethrins, rotenone, and spinosad (technically a biological control) are some of the botanical insecticides you’ll find. Products may contain more than one organically acceptable pesticide. There also are organic fungicides, including various sulfur sprays and dusts, as well as products that contain Bacillus subtilis. While organic sprays and dusts tend to be less harmful to the environment than synthetic controls, they should be used as a last resort only after other controls fail.
Q Why are organic controls better than regular garden sprays?
A One reason is that they biodegrade quickly. Pyrethrins, for example, are persistent for only a few hours in sunlight when temperatures are above 50°F/10°C. Neem lasts 3 to 7 days on plants and a few weeks in the soil. Rotenone is effective against a wide spectrum of insects, including caterpillars, flies, and beetles. It has a short lifetime in the environment, but it is extremely toxic to fish. Keep in mind that all of these pesticides are toxic to beneficial insects such as lady beetles, and even though they are organically acceptable, you should follow label directions very carefully when using them. Also label your pesticide sprayer so you don’t mistakenly use it to apply fertilizer.
Q How do soap sprays kill insects? I’ve heard that they can damage plants, too.
A Available at garden centers, soap sprays (nontoxic to humans) are very effective for killing slow-moving, soft-bodied pests like aphids, spider mites, white-flies, and thrips. They’re not very effective for controlling hard-bodied pests like beetles. To make a soap spray more effective, add ½ cup/118.3 ml rubbing or isopropyl alcohol to 1 quart/.95 l of spray.
Soap sprays can cause the leaves of some plants to turn brown, especially if the weather is hot and/or humid. For this reason, it’s best to spray on an overcast day and avoid using soap sprays when temperatures exceed 80°F/26.6°C. To determine which of your crops could be damaged, mix up a batch of soap spray and spray it on a leaf or two of each crop you are growing. (Be sure to mark the leaves you have sprayed with yarn, string, or ribbon.) Check for damage after 2 days, and make a list of the crops that the spray damaged. Store this list with your spraying equipment so you know what plants to not spray. Still, if you need to spray a crop that may be damaged by your soap spray, try this trick: 3 hours after spraying, hose off the plant’s leaves. The soap will have taken care of the pests, and removing the remnants of the spray helps avoid the damage.
Q Are there organic spray products besides insecticidal soap?
A Horticultural oil, long used to control a wide variety of pests in orchards and on woody ornamentals during the dormant season, also can play a role in the food garden. Look for highly refined oils (viscosity of 60 or more), and read the label very carefully to determine the growing season dilution. (You’ll see that there’s a separate dilution for use on dormant plants in wintertime, when the spray can be stronger.) To make horticultural oil more effective, after diluting it, add a squirt of liquid dish soap.
Since oil sprays can be poisonous to plants, before spraying be sure to test oil sprays on a leaf of your plant, then wait 24 hours before spraying. Horticultural oils are effective for killing aphids, spider mites, caterpillars, and other soft-bodied pests. They also prevent some fungus diseases, yet they don’t persist very long in the environment and are relatively harmless to beneficials.
Horticultural oils are a petroleum product, but newer oil sprays depend on plant oils to control pests. Some also are useful for controlling powdery mildew and other plant diseases. Clove, mint, rosemary, and cinnamon oils have all demonstrated insecticidal properties: Formulations of these oils, alone and in combination, are available from companies that sell organic gardening products.
Q Is there a homemade spray I can use to fight insect pests?
A Soap-and-oil spray is the easiest homemade spray to make and is very effective for controlling a wide range of pests. Start by mixing a concentrate solution to keep on hand by combining 1 cup/.24 L of vegetable oil and 1 tablespoon/14.8 ml of liquid dish soap. To dilute this mixture to use in your garden, combine 2 teaspoons/9.86 ml of the concentrate with 1 cup/.24 L of water. Put the mixture in a hand sprayer and spray it on infested plants. Be sure to wet both tops and undersides of leaves.
Q What products can be used to control diseases?
A Farmers and gardeners have used sulfur and copper sprays to fight plant diseases for a century or more. Many products that contain sulfur and copper are acceptable for organic gardens, but check out some of the newer disease control products, too. Fungicidal soaps are one option, as well as sprays based on potassium bicarbonate as the active ingredient. There are even products that harness the fungus-fighting power of a naturally occurring soil bacterium called Bacillus subtilis.
Q If I see a pest or damage in the garden, how do I decide what to do about it?
A First, don’t simply assume that a nearby insect did the damage, unless you see it feeding. The insect or insects you see may be innocent or may be beneficials that have already dispatched the pest. Use the pages that follow to identify what’s attacking your plants. It’s helpful to have a garden insect guide handy, too, so you can identify any unfamiliar insects you encounter.
SEE ALSO: For garden insect guide suggestions, Appendix.
Q The leaves and/or stem tips of my vegetable plants are curled up and distorted. What’s causing this problem?
A Several pests, along with one disease, can cause curled or distorted leaves. Some of them are listed below.
Aphids are tiny pear-shaped insects found in dense clusters. They may be white, green, black, gray, or pink; they excrete sticky honeydew on leaves. Leafhoppers are wedge-shaped insects that jump and fly in all directions when startled. Their nymphs lack wings.
Aphid
CONTROLS: Blast aphids and leafhopper nymphs with a strong stream of water; attract beneficial insects; use insecticidal soap. As a last resort, spray neem or pyrethrins.
Leafhopper
Leafhoppers spread this disease, which causes curled, stunted leaves and dwarf plants. Pull up any infected plants you see, for there is no cure.
Both the ½"/6.35 mm-long light green to brown adults and the yellow-green nymphs suck plant juices and cause leaves, stems, flowers, and fruit to become distorted and drop. Several other closely related insects cause this problem.
Tarnished plant bug
CONTROLS: Cover plants with floating row covers (hand pollinate flowers, as necessary); attract beneficial insects. As a last resort, Tarnished plant bug spray insecticidal soap or pyrethrins.
Look closely for webbing on the stem tips and for clusters of tiny (1/50"/.5 mm) eight-legged mites.
Spider mite
CONTROLS: Wash mites off plants with water; spray insecticidal soap. Use neem as a last resort.
Q Light green patches developed on my squash and pumpkin plants; then the leaves and stem tips died. What caused that?
A Squash bugs have been feeding on your plants. Both the adults (½"/12.7 mm-long brown-black insects) and the whitish green juveniles suck plant juices. Infested plants won’t produce fruit.
Squash bug
CONTROLS: Handpick the insects from underneath the leaves or lay boards on garden rows to trap them: The insects will hide under the boards and can be handpicked. Floating row covers will keep these pests away from plants, but you’ll need to hand-pollinate the flowers to get fruit. As a last resort, spray squash bugs with insecticidal soap, pyrethrins, or neem.
Q There are spots on the leaves of my vegetable plants. What could have caused them?
A Lots of small yellow spots are one of the early signs of a spider mite infestation, so look closely for webs to identify these tiny pests. Several other pests and diseases can cause this problem, including tarnished plant bugs, whose feeding eventually results in wilted leaves and stem tips. Other causes can include any of the following:
These pests rasp leaves and cause silver streaks or speckling on the leaves and flowers. In severe cases, they can stunt plants. CONTROLS: Encourage beneficial insects; spray insecticidal soap, pyrethrin, neem, or spinosad.
Thrips
This fungal disease causes yellow or white spots on the tops of leaves and orange ones beneath the foliage. CONTROLS: Ensure good air circulation by spacing out crops; do not wet leaves when watering plants; dust plants with sulfur powder as a preventive or to keep a mild infection in check.
Many different plant diseases begin as spots on the leaves. One example is downy mildew, which causes yellow spots on the tops of the leaves and corresponding cottony blotches on the undersides that are white, gray, or tan. Unfortunately, it can be difficult to identify which specific disease is infecting your plants.
CONTROLS: One way to avoid many foliage diseases is to plant resistant or tolerant cultivars. Picking off afflicted leaves or pruning off infected growth are other effective tactics. Pruning to increase air circulation can reduce problems with many diseases. But if plants become moderately to severely infected, pull them up and be sure to dispose of them in the trash, not the compost pile.
SEE ALSO: For information about spider mite infestation, page 147; for tarnished plant bugs, page 148.
Q Ugh! There are great big holes in the leaves of my plants! What do I do about them?
A Large holes in leaves — or leaves that have been eaten away altogether — are one of the most common signs of a pest invasion. Here are some of the possible culprits:
If you see slimy or shiny trails on the leaves, slugs or snails are the culprits. These pests hide under mulch, rocks, and other objects during the daytime and feed at night. They pose the biggest problem in wet weather.
CONTROLS: Trap these pests under boards, cabbage leaves, flowerpots, or other objects, then scrape them into a bucket of soapy water to dispatch them. Or lure them to containers filled with stale beer: Set containers with the lip at soil level so that slugs and snails are lured in and drown. Surrounding plants with a band of wood ashes discourages them as well, as long as you renew it frequently. Attracting birds, toads, and other beneficial animals to the garden also helps control slugs. Organic slug and snail bait also is available. The active ingredient is iron phosphate and Sluggo is one brand name to look for.
slug
Various caterpillars feast on vegetable foliage, chewing large holes in leaves or devouring leaves completely.
CONTROLS: All caterpillars can be controlled by hand-picking or by spraying with Bacillus thuringiensis (Bt). Attracting beneficial insects will decrease problems with caterpillars, and if you see any that seem to be sick (they’ll be sluggish or yellowish in color, or have ricelike cocoons on them), leave them alone and let the disease or the parasitic wasp spread to other caterpillars. Spinosad is also effective against caterpillars.
If you see ¼"/6.35 mm-long yellow and black beetles — either spotted or striped — cucumber beetles are eating your veggies. Both feed on a wide variety of vegetables, and both carry various diseases that cause plants to wilt and die suddenly.
Striped cucumber beetle
CONTROL: Use floating row covers on seedlings, and hand-pollinate crops such as squash and melons that need it to produce fruit. Apply parasitic nematodes to the soil to control the beetles’ larvae, and spray pyrethrin or rotenone to control the adults. Kaolin clay is also effective against cucumber beetles. Be sure to clean up the remains of crops and dispose of them in the trash, since these pests overwinter in them.
Various animal pests can also chew leaves and plant parts, so don’t overlook them. Deer may eat entire plants, but they also can browse off the tops of your vegetables. Crows have been known to pull up seedlings and consume them, and rabbits are eager to chomp away at all manner of vegetable plants.
CONTROLS: See pages 163-167 for information on controlling these pests.
Q My bean plants have holes chewed in them, but the damage has a lacy look, since most of the leaf veins are still there. What insect could be causing such damage?
A Mexican bean beetles are oval, yellow-brown pests that are ¼"/.64 cm long and have black spots on their hard wing covers. (Bean beetles look somewhat similar to lady beetles.) Both the adults and the bristly orange-yellow larvae feed from underneath the leaves, chewing holes and leaving a skeletonized pattern. The adults lay clusters of yellow-orange eggs shaped Mexican bean beetle like grains of rice.
Mexican bean beetle
CONTROLS: Avoid the main generation of beetles by growing early-season bush beans; grow beans under floating row covers until the plants are large enough to tolerate any damage. Plant soybeans nearby to attract the beetles, then destroy the plants once they’re infested; handpick adults and larvae daily and drop them in a jar of soapy water; attract beneficial insects. As a last resort, spray every week with insecticidal soap or neem, or rotenone. Kaolin clay is also effective against these beetles.
Q The leaves on my eggplants and other vegetables are just covered with tiny holes. What pest might have caused them?
A Look closely, and you’ll see tiny, shiny black beetles that hop away whenever you disturb them. These are flea beetles, and they chew holes in leaves. They also spread diseases.
Flea beetles
CONTROL: Use floating row covers to protect seedlings and transplants early in the season. For later infestations, spray with spinosad; kaolin clay is also effective against flea beetles.
BACILLUS THURINGIENSIS, or Bt, is a safe and effective control for caterpillars and beetle larvae, yet it doesn’t harm beneficials. Unlike conventional insecticides, it is a toxin that is produced by a bacterium. Several subspecies are available, some for caterpillar control and others for beetle larvae, so read labels and make sure the one you purchase will control the pests that are eating your plants. Bt is available in several formulations: liquid concentrate, a powder that is mixed with water before spraying, and in dust or granular form.
Applying Bt correctly is a must if it is going to work properly, because the pests need to eat it as they munch on plant leaves. Spray it on both upper and lower leaf surfaces, and make sure to coat the stems. Be aware that it doesn’t persist for long in the environment and degrades especially quickly in sunlight. Bt is most effective on young larvae and won’t kill adults, so apply it as soon as you see caterpillars or beetle larvae. Reapply every 7 days to manage persistent populations of pests. Keep in mind that it will kill all caterpillars, including those of butterflies, so spray infested plants only, and never apply it to plants where butterfly larvae are feeding.
Q My seedlings fell over, but the tops still look okay. Can I prop them back up?
A Unfortunately, your seedlings are probably done for. If you take a close look at the base of the damaged seedlings, you’ll discover what caused the problem:
If the base of the seedlings look dark, sunken, and/or soft and rotted, the problem is damping-off, a fungal disease.
CONTROL: For seedlings indoors, to prevent damping-off, disinfect pots with a 10 percent bleach solution (1 part bleach, 9 parts water). Also, use pasteurized seed-starting mix, water seedlings from the bottom, and run a small fan continuously to circulate air. Spray seedlings with compost tea once the first true leaves emerge.
If the problem is out in the garden, you’ll want to take a different approach, since eliminating the fungus that causes damping-off isn’t practical, and healthy soil contains loads of microorganisms that help control it. Improve soil drainage by working compost into the soil, check the soil temperature before you sow, and don’t sow too early, when the soil is still too cool. Also, don’t sow the seeds too deeply, because the longer the germinating seedlings are underground, the more susceptible they are. To be sure air can circulate, don’t sow seeds too thickly. Finally, water plants in the morning so they dry out by nightfall, and try to keep the soil evenly moist but not sopping wet.
These chubby, 1"/2.5 cm-long brown or gray caterpillars live in the soil. Cutworms chew through the base of seedlings and transplants and also can eat them entirely. CONTROLS: When transplanting, slip a cutworm collar over each seedling as you plant it. To make cutworm collars, cut 2"–3"/5–7.6 cm-long sections of cardboard tubing (toilet paper or paper-towel tubes are perfect). Push the collars into the soil around each plant; they’ll provide protection until the plant is large enough that it’s no longer of interest to the cutworms. Another cutworm control is to mix bran cereal with Btk (Bacillus thuringiensis var. kurstaki) and spread it around all the transplants. Or spread parasitic nematodes a week before transplanting. These are available from companies specializing in organic controls.
Cutworm collar
Q My transplants disappeared overnight! Where could they have gone?
A A variety of pests play this unkind trick! Cutworms can eat seedlings and transplants entirely, instead of just cutting them down. Slugs and snails also can be quite voracious: Look for their slimy or silvery trails to see if these pests are the culprit. Armyworms are another pest that will consume plants entirely. They feed at night (as do cutworms, slugs, and snails) and hide in leaf litter or under rocks during the day. Look for greenish brown caterpillars with white stripes running along Armyworm their backs.
Armyworm
CONTROLS: To help control any of these pests, take steps to attract beneficial insects, as well as toads and frogs to your landscape. Spray armyworms with Btk (Bacillus thuringiensis var. kurstaki). Use kaolin clay to discourage adults from laying eggs on target plants.
SEE ALSO: For more slug and snail controls, page 151.
Q My squash plants died! First one branch seemed to wilt, then the entire plant wilted and died really quickly — almost overnight. What happened?
A Both insects and diseases can cause this problem:
These caterpillars tunnel into the stems of squash plants and eat out the centers of the stems, causing plants to wilt suddenly. The adults are greenish brown moths with red abdomens, but it’s the white larvae, which have brown heads, that cause the damage.
Squash vine borer
CONTROLS: Cover plants with floating row covers, but uncover them when flowers appear so bees can reach them or hand-pollinate. Heap a shovelful of soil over leaf nodes at various intervals along the vines, and then water them to encourage root formation. Look for entry hole(s) at the base of the stem with frass (chewed plant material) coming out of the hole. Slit the vine lengthwise and carefully pull open the stem to reveal the borer. Crush borers as you find them. Close up the vine and cover the slit with about 1"/2.5 cm of moist soil. Water the spot with compost tea for a few weeks to encourage roots to form. You can also look for borers with a flashlight at night: Hold it next to the stems and look for silhouettes of the pests in the stems. Pierce them with a hatpin. Repeat this activity every 2 or 3 days until you don’t see any borers.
If you don’t see an insect, suspect a wilt disease such as bacterial, fusarium, or verticillium wilt. These disease organisms gum up the internal transport system of the plants, blocking the flow of water to the top of the plant and causing it to collapse.
CONTROL: If you suspect a wilt disease, plant resistant cultivars in the future. Pull up afflicted plants and dispose of them in the garbage, not the compost pile.
Q My cabbage plants started wilting during the middle of the day, but watering didn’t seem to help them. Now they’re really stunted looking. What should I do?
A You’ll probably have to give up and try again. Here’s what could be causing the problem:
Cabbage maggots (fly larvae) bore into the roots of cabbage, broccoli, and other cabbage-family plants. The damage they do to roots causes plants to wilt at midday, but their feeding also makes it easy for disease organisms to attack as well.
CONTROLS: Pull up and discard the roots of cabbage-family plants; don’t add them to compost. Use floating row covers to prevent adults from laying eggs on transplants, and be sure to secure the edges of the covers with soil to keep adults out; spread parasitic nematodes along the row up to a week before planting. To stop females from laying eggs around the base of transplant stems, cut 5"/12.7 cm-wide circles or squares out of tar paper, scraps of rubber pond liner, or foam rubber. Make a slit to the center of the circle and cut a very small opening to accommodate the plant’s stem. Place these barriers around seedling stems.
Cabbage maggot fly barrier
This fungus disease can cause these symptoms as well. Pull up an afflicted plant, and you’ll find a gnarled mass of roots.
CONTROLS: Pull and destroy infected plants and discard them in the trash, not on the compost heap. To prevent this disease, raise the soil pH to 7.2, because the fungus that causes it requires neutral to acid conditions.
Q Whenever I walk past my vegetable garden, clouds of tiny white insects fly up. Will they eventually cause a problem?
A What you have in your garden are probably white-flies, tiny insects with white wings that hide under leaves and fly up when disturbed. They suck plant sap and also excrete sticky honeydew, which supports the growth of sooty mold on the leaves. These insects also can spread viral diseases. Eventually their feeding will weaken plants.
CONTROLS: Inspect plants carefully at garden centers, since whiteflies are often carried home on purchased plants; attract beneficial insects; spray with insecticidal soap or neem.
Q I don’t see any insects on my leaves, but the leaves look like they’ve been dusted with talcum powder. What causes that?
A Leaves that are dusted with white or gray are infected with powdery mildew, which also can cause distorted growth. Unlike many fungal diseases, which pose the biggest problem in cool, damp weather, powdery mildew is at its height in the garden when days are hot and nights are cool.
CONTROLS: Pick off individual leaves that are infected, prune to improve air circulation, or spray with sulfur. Ordinary baking soda (sodium bicarbonate) is effective as well but is best applied beginning 2 weeks before symptoms appear. Dilute 1 teaspoon/4.9 ml baking soda in 1 quart/.95 L of water. (Commercially available bicarbonate, potassium bicarbonate, is also used for this purpose.) Surprisingly, milk is another option you may want to try. Add 1-2 tablespoons/14.8-29.6 ml of milk to 1 cup/.24 L of water and spray on foliage; milk is best applied before symptoms appear as well.
Q Something big is eating my vegetables! Whatever it is takes big chomping bites out of leaves or takes off entire tops of plants. I never see what it is, though, so how can I control a pest that I don’t see?
A Most animal pests feed in very early morning or late in the evening, and it can be difficult to tell just what is damaging your crops. Look carefully during those times of day to see if you see pests like rabbits, groundhogs, deer, or birds feeding. Look for signs that each animal leaves, such as footprints, feces, and feeding patterns — deer chomp away at plants from the top, rabbits from the bottom, for example. Birds can peck at fruits and vegetables and will pull up seedlings, and larger pests can make plants disappear entirely, so it’s important to figure out what you’re dealing with.
Q I’ve got deer and rabbits eating me out of house and home! What should I do?
A For all land-bound pests, including rabbits and deer, fencing is the best option. The best time to erect a fence, though, is before the animals learn that you’re cultivating tasty produce. Other controls give varying results. Some gardeners swear by them; others say they don’t work at all. Pests faced with hunger and overpopulation are much more determined than ones that aren’t, so deterrents will be less effective on desperate creatures. Nevertheless, try some of the following:
HANG BAGS OF FRAGRANT, HEAVILY PERFUMED SOAP on stakes throughout your garden. (Place some close to the ground if you are trying to deter rabbits.) Leave paper wrappers in place and drill a hole through the bar. Mist the soap with water in early evening, just before deer begin to feed. Soap will keep pests at bay until they become accustomed to the fragrance.
HANG BAGS OF HUMAN HAIR (you can collect this at beauty shops). Renew them frequently.
COMBINE 2½ GALLONS/9.5 L OF WATER WITH SIX EGGS (don’t include shells, which will clog the sprayer), then spray the mixture around the perimeter of your garden. Humans won’t be able to detect the smell of the rotting eggs, but deer will. Reapply after a rainfall.
SPRINKLE A MIX of half bone meal and half blood meal around plants (both of these substances are available at garden centers). Renew after a rainfall.
LIGHTS OR SPRINKLERS that are activated by motion detectors also have been effective at controlling deer.
CAGING INDIVIDUAL PLANTS or sections of your garden is quite effective. Try lightweight wood frames covered with chicken wire.
SEE ALSO: For information on fencing, page 166.
Q What about trapping pests? I have resident rabbits and groundhogs, but I don’t want to kill them.
A You can use Havahart traps to capture pests and move them to another area, but in most cases other individuals will move in to the now-empty territory. Your relocated captives also won’t necessarily fare well at their release site, so this often isn’t a humane alternative to wildlife control. They’re likely to be killed or driven away by other animals that already have laid claim to the territory. Finally, it’s important to have a plan in mind in the event that you trap an unexpected pest, such as a raccoon, which might be rabid, or a skunk, which can be a trial to transport. If you do choose to move wildlife, make sure it is legal in your area, and release animals at least 1 mile/1.6 km away from your house — farther is better. For a long-term solution, fencing is more effective.
Q What kind of fence will keep all the local critters out of my garden?
A In a smaller garden — 60'×40'/18.3×12.2 m — a 3'/.9 m-tall fence will keep deer at bay, since they don’t like to jump into a confined area. Ordinary snow fencing works fine for this purpose. If your garden is larger, for a single fence to be effective, it needs to be 8'/2.4 m tall to prevent deer from jumping over it. Or consider installing two shorter fences, which actually are quite effective because deer find it difficult to jump both fences. Try a 4'/1.2 m-tall chicken-wire or wire mesh fence with a single strand of electric fencing located 2½'/.76 m off the ground and 3 feet (.9 m) outside the first fence. (To prevent raccoons, use a three-strand electric fence, with strands separated 3"–4"/7.6–10.2 cm, and the lowest strand 3"/7.5 cm off the ground.) Electrified-netting portable fence, which comes in a roll with posts installed in the netting, is another easy solution for keeping a wide range of critters at bay. They’re also easy to take down at the end of the season for garden cleanup.
Garden fence with underground extentsion
Since rabbits and groundhogs tend to dig under fences, install the fence with an underground extension as shown, or dig a trench around the base of an existing fence and line it with chicken wire. Bend the lower edge of the chicken wire out at a 90-degree angle. You can also reinforce an ordinary picket fence with chicken wire if rabbits are your primary pests: Attach a 2'-3'/.6 or .9 m-wide section to the base of the fence, and ideally, use it to line a trench dug along the base of the fence.
Q How can I stop birds from uprooting seedlings? Obviously, a fence isn’t going to be effective.
A Covering plants with floating row covers or lightweight plastic netting is an effective way to keep birds away from your crops. Scare tactics work as well. Try suspending unwanted CDs, aluminum pie plates, or any other shiny materials that move in the breeze. For best effect, change their locations frequently. Moving a scarecrow around the garden also can be effective (and fun!). Rubber snakes, owl decoys, and bird-scaring balloons also help control pests.