As organic fruit growers dealing with a whole-systems (holistic or ecosystem) approach, we need to integrate many pest management strategies into our overall orchard management plan. We place the emphasis of our prevention and pest control programs on beneficial organisms and cultural practices. Organic pesticides are also key elements in the program, after we have done everything else we can.
Fruits and fruit trees are valuable sources of food and/or habitat for many different pests. Mammals, large and small, feed on the fruits, twigs, buds, bark, and roots of the trees. Many bird species feed on fruits, and woodpeckers and sapsuckers damage the trunks. Insect and mite pests attack fruits, leaves, stems, and trunks, and certain nematodes can damage roots. Fortunately, careful planning and management can control most of these pests.
Moose are common and sometimes devastating pests for orchardists in northern latitudes across much of North America. From personal experience, I know that a single moose can destroy a remarkable number of fruit trees in a very short time. Deer are also serious orchard pests in many areas of North America.
Fruit growers have tried using repellant sprays made from rotten eggs or pepper, soap bars, bags of human hair, skunk and coyote urine, and many other repellant materials. The fact is that none of the materials works particularly well for more than a few days, and none will protect an orchard from hungry moose or deer. Noisemakers and visual scare devices have fared no better. Moose and whitetail deer have proven remarkably adaptable and quickly lose their fear of such things.
Large herbivores are best managed using exclusion fences. Many different types of fences are used for protecting orchards, and most work fairly well. At the high end, a New Zealand–style electrified fence made up of strands of high-tensile wire spaced about 10 inches apart and 8 to 12 feet tall works well for moose but is not reliable for deer. Single-strand fences, in general, are not effective against deer, which push through or under fences readily, even if the strands are electrified or made of barbed wire.
Some growers have used a double-row fence made up of two short (5 to 6 feet high) fences spaced about 4 feet apart. The theory is that deer are good at jumping heights but not particularly good at jumping long distances and hesitate to jump into the narrow space between the two fences. One creative Pennsylvania orchardist installed a single short fence, then placed short-legged dogs bred to herd reindeer in the orchard. The dogs could not run fast enough to catch or hurt the deer, but they were still effective at keeping the deer out.
The most effective means of excluding large herbivores is to use a fence that has about a 4-by-4-inch or smaller mesh along the bottom 5 feet, with wider mesh or single wires spaced 12 inches apart composing the rest of the fence to a height of at least 8 feet.
Mesh and single wire fence. The 4-inch-square mesh is 5 feet high with single-strand wires above spaced about 10 to 12 inches apart to a height of 8 feet.
Double fence. The mesh fences are 5 to 6 feet high, spaced about 3 to 5 feet apart.
New Zealand electrified fence. The fence is 8 to 10 feet tall with every other wire electrified, starting with the bottom wire.
Keeping the mesh portion of the fence firmly on the ground provides the best deer control, but it also excludes foxes, coyotes, and other predators that feed on mice and voles that can attack your trees. An alternative is to keep the fence at ground level around the perimeter but leave a few small (1 foot square) openings in the fence for the predators to pass through and install a second barrier fence just inside or outside the opening to block the taller and longer deer. A similar design is often used for schoolyard fences to allow people to pass through but block bicycles and other vehicles. Keep the opening just large enough for a coyote or fox to squeeze through. Deer fawns are small and remarkably adept at crawling through or under fences. Figure 11.1 shows typical orchard fence designs.
Inexpensive nylon mesh fences resembling tall plastic chicken wire are marketed as deer fencing for orchards and gardens. While they are not as durable as metal fencing, they are less expensive and for several years proved surprisingly effective in protecting fruit plots from whitetail deer on one of my research farms. How well they work against moose is questionable. These fences are probably best used for home orchards or to provide temporary protection in larger orchards.
If raccoons or porcupines are a problem in your orchard, use a fence with small mesh and add electrified wires at the top, angled outward. Electricity can be produced using solar panels, although this strategy is not always effective during winter at high latitudes with very short days.
Regardless of the fence you choose, make sure the posts and corners are strong enough to support it. Keep the fence tight, especially at the bottom. Watch out for low spots, particularly where the fence crosses over gullies or water. An Alaska fruit grower that I worked with suffered damage to his crops when a moose calf fell into a bog at the edge of his nursery and swam under the fence where it crossed the bog. Once inside the fence, the calf was unable to find its way out again and survived by eating the fruit trees and bushes. The fence did keep out the cow moose, however.
Rodents and rabbits can cause serious damage to an orchard by girdling trunks or feeding on roots. Because they are small, exclusion is generally not an option. Even if you use a small mesh fence to the ground, rabbits and other pests can tunnel under the fence. These pests can be managed in several ways.
Traps. Hand trapping is effective against pocket gophers and other larger, burrowing rodents. Trapping has generally proven more successful than using poisoned baits, as the pests learn to recognize the baits and avoid them. Anchor the traps firmly to the ground to prevent dogs and other predators from carrying away the trap after a gopher has been caught. Check the traps at least three times a week, from spring through fall.
Bare ground. Maintain bare ground within the tree rows using weed barrier fabrics, organic mulches, thermal weeding, organic herbicides, mechanical cultivation, and hand weeding. If this strategy does not fit into your orchard management plan, you can keep in-row cover crops and alley crops mowed short, particularly going into and through the winter. During the growing season, mow alternate rows every two weeks to reduce rodent habitat. If you blow mulch into the rows or grow in-row cover crops, plan an aggressive rodent control program.
Mice guards. Install wire mesh mice guards around fruit tree trunks to a height of at least 3 feet (these pests can use snow as an elevator to reach quite high up on trunks). Use galvanized hardware cloth with about 1⁄4-inch mesh. Bury the bottom of the guard several inches in the ground and make it large enough in diameter so as not to girdle the trees. Use easy-to-remove fasteners to hold the edges of the hardware cloth together to allow easy removal of the tree guard for pruning and other trunk maintenance. Figure 11.2 shows such guards.
Wire mesh guards prevent rodents and rabbits from damaging tree trunks.
Good sanitation. Remove all plant debris in and around the orchard and compost, burn, or bury it. Don’t keep brush piles or piles of wood or other materials. Harvest ripe fruits promptly. In barns and sheds, keep seeds and other plant materials that are attractive to rodents in sealed, plastic containers.
Cats and dogs. Cats and terrier-breed dogs have well-earned reputations as mousers and can also aid in managing gopher populations in small orchards. Consider keeping several neutered or spayed cats and dogs in your orchard.
Raptors and owls. Install raptor and owl perches and owl nesting boxes in and around your orchard. Providing habitat for these predators will help manage mammal and bird pests.
Insect-eating birds are great beneficials. Some birds, however, can damage large amounts of fruit, often taking only a few pecks at a fruit but rendering it unfit for consumption. Bird damage is usually most serious in small orchards, where a few birds can destroy a relatively large percentage of the fruit. In large orchards, there is simply too much fruit for the birds to damage more than a very small percentage. As with deer, visual scare devices and noisemakers (including bird distress calls) work only for a very short time.
Site selection. If possible, avoid planting your orchard near woodlots that provide nesting and perching areas for birds.
Bird netting. For small orchards, install fine mesh bird netting over the trees and bushes. Put out the netting just before the fruits ripen, and keep the netting taut to prevent birds from becoming entangled. Mount the net so that it can easily be moved aside during harvest. Remove the netting immediately after the harvest is done.
Perches and nest boxes. Install raptor and owl perches in and around the orchard. To reduce predation on beneficial birds, keep the raptor and owl perches away from nesting boxes and other nesting areas. Install owl nesting boxes around the perimeter of the orchard near the owl perches. Face the boxes away from the nesting areas of beneficial birds, as we will discuss later in this chapter.
Many insects, mites, and nematodes feed on fruit crops, and several cause severe and widespread problems in North America. Plum curculio, apple maggot, and codling moth are the three most serious pests.
In natural ecosystems, we usually see balances of plant pests and predators that feed on those pests. Many serious pest outbreaks can be traced to the introduction of exotic insects, mites, or nematodes that have no predators or diseases in the new areas to control their numbers. There are exceptions, of course. Plum curculio, long a limiting factor in organic fruit production, is native to North America. Growing crops in large monocultures can also upset the balance in favor of the pests.
Conventional fruit growers rely heavily on a wide variety of insecticides, miticides, and nematicides to manage pests in their crops. Although organic growers have gained a few powerful pest control products in recent years, using cultural practices to develop an orchard ecosystem with a balance of pests and predators is still the best pest control strategy. Unlike with diseases, we have few fruit varieties that are resistant to pests.
The orchard floor management practices we discussed in chapter 9 play important roles in managing insects, mites, and nematodes, mostly by providing habitat for beneficial organisms. Because pest and disease pressures vary from one growing region to another, you will need to tailor those practices to your specific location.
Pest management is highly complex in all but the smallest orchards. Cultural practices must be integrated to reduce pest populations while protecting and enhancing beneficial populations. Tree nutrition, orchard floor management, pruning and training, use of insectary crops, pheromones to monitor (and sometimes reduce) pest populations, pest repellants, and pesticides all play roles in an effective orchard pest management program.
As with disease management programs, scouting is extremely important in any orchard pest management program. During the growing season, spend at least 3 days per week in your orchard looking for signs of pests or the damage they leave behind. Useful scouting tools include a jeweler’s magnifying loupe, a white sheet of poster board or a commercial beater tray, and a short stick. The loupe is helpful in locating and identifying mites, thrips, and other small organisms. By holding the poster board or beater tray under a branch and tapping on the branch with a stick, you can collect many pests that would otherwise be hard to spot.
A very helpful way to monitor apple maggot populations is to hang red, apple-shaped spheres smeared with petroleum jelly or other sticky material from the trees. Both yellow and white sticky cards placed throughout the orchard are valuable for monitoring pest and beneficial populations. Commercially manufactured cards are available from orchard and nursery supply companies, or you can easily make your own from poster board. Cut the board into 4- to 6-inch square cards. Attach a string for hanging the cards from the trees, and coat the cards with petroleum jelly, or spray them with vegetable cooking oil. Likewise, pheromone-baited sticky traps can be used to monitor populations of codling moth, Oriental fruit moth, and other insects. We’ll discuss these steps as they are used with specific pests. Figure 11.3 shows typical traps for monitoring insect pests.
Red sticky spheres are commercially available and are useful in monitoring for apple maggot.
White, blue, and yellow sticky cards can easily be made and are also commercially available. They attract a wide assortment of insects.
Pheromone traps come in various sizes and shapes. Tent traps are very common and are used to monitor codling moth, Oriental fruit moth, and other pests. Pheromone baits attract insects to the traps.
As for the rodent and disease control programs, maintain a clean farmscape to manage pests. Remove and destroy or compost crop wastes promptly. Burn heavily pest-infested plant residues. If prunings cannot be removed from the orchard, use a flail mower to chop them into small pieces as soon after pruning as possible.
Beneficial insects, mites, nematodes, birds, and bats play vital roles in organic pest control programs. If beneficials are wiped out, a pest population can explode in a matter of days or weeks.
Managing natives. While you can purchase and release beneficial insects, mites, and nematodes, the best strategy is to manage those beneficials that occur naturally in your area. The huge advantage is that they are adapted to the climate and can provide abundant, long-lived populations.
Begin by learning to identify beneficial organisms that are native to your area. Integrated pest management specialists and entomologists at universities and state and provincial agricultural organizations can supply this information, much of which is readily available online. Particularly good guides and programs are available from Cornell University in New York, Pennsylvania State University, Washington State University, and the University of Kentucky. Common beneficials include green lacewings, ladybird beetles (ladybugs), big-eyed bugs, damsel bugs, parasitic wasps, and predatory mites.
Using the resources mentioned above, learn to identify beneficials in your area, and conduct a survey on your site to determine which beneficials are present and how large the populations are. Repeat this survey each year at the same time to monitor your pest management program.
Releasing beneficials. If you plan to release beneficials in your orchard, the most effective will be beneficials that are native to your area but not to your site. Nonnative beneficials might be useful in certain circumstances, but they seldom produce long-lived populations and must be released on a regular basis. Be very cautious in releasing nonnative organisms, as they often disperse out of the orchard and you do not want to accidentally introduce another exotic pest into the ecosystem.
Growing insectary crops. In chapter 9 (see page 306), we discussed the use of insectary crops. Insectary crops provide food, shelter, and egg-laying sites for beneficial insect and mite adults and/or juveniles. Pollen, nectar from flowers, and exudates from the glands on plant stems and leaves are important food sources for certain beneficial insects during at least part of their life cycles.
In many cases, insectary crops support prey for the beneficials. The prey might be the same pests that attack your fruit crops, related species, or an unrelated and innocuous insect or mite. The important point to remember is that without prey to survive on, predators and parasites will either die or move out of the orchard to areas where prey are available. In conventional orchards, fruit growers often try to eradicate a pest using insecticides or miticides. In organic systems, the goal is to maintain pest populations that are too low to cause significant damage to your crops but large enough to support healthy populations of predators and parasites.
Common insectary crops include dill, chamomile, hairy vetch, spearmint, Queen Anne’s lace, buckwheat, yarrow, white clover, cowpea, cosmos, and other species. Some grasses, particularly those that have glandular leaves, can also provide habitat for beneficials. In some cases, you might be able to include herbal or ornamental crops in the insectary planting for cash flow or personal use. Using a mix of plants that flower throughout the summer can help support bees that you can use to pollinate your orchard in spring.
One strategy for an organic orchard is to maintain a planting of insectary crops within 50 feet of all trees. This might be accomplished by including insectary crops in alleyways, in in-row plantings using the “sandwich system” described in chapter 9, or in non-tree rows throughout the planting.
Don’t forget that many animals feed on insects, chief among them being birds and bats. Start by finding out which species of birds and bats in your area feed on insects that might become pests in your orchard. Learn about the nesting habits and living requirements for these beneficial birds and bats, and design nesting facilities and perching sites to support them in and around your orchard.
If you live in an area where bluebirds live, for example, consider installing nesting boxes on the fence line around your orchard. About 80 percent of a bluebird’s diet is insects. Be aware, however, that the other 20 percent comes from berries and fruits from small trees and bushes. You want to maintain enough of a bird population to help control insects without seriously damaging your fruit.
Swallows feed almost exclusively on flying insects, often over fields and water. They construct nests under building eaves, in barn lofts, in culverts, and in cliff pockets. Chickadees eat seeds and berries, but much of their diet, even in winter, consists of insect adults, larvae, and egg cases. Wrens are aggressive birds that subsist almost entirely on insects. While wrens can be valuable assets in an orchard, however, they also attack the eggs of other cavity-nesting birds, such as bluebirds. Give some thought as to how well the different species of birds in your area will work together in your orchard before building nesting boxes and other facilities to support them. Remember to supply sources of clean water for your bird and insect beneficials. Birdhouse plans for many species of North American birds are available online.
Chickens have long been used in orchards and gardens to control insect pests. They eat adults and larvae and are especially valuable in scratching up and eating pupae in the soil, including apple maggot. Unfortunately, organic certification programs generally do not allow livestock, including chickens, in a fruit planting within a certain timeframe before harvest. The reason is to reduce the likelihood of human pathogens contaminating the fruits. Organically certified tree fruit growers will need to remove the chickens from the orchard at least 90 days before harvest, and bush fruit growers will need to do so 120 days before harvest. In such situations, consider placing chickens in the orchard immediately after harvest to help reduce the number of overwintering pests. Use pens and fences to manage the chickens and protect them from predators.
Many bat species live on insects. The little brown bat, for example, is native to the northern United States and Canada as far north as the Yukon. Bats can consume half their body weight each day in insects, and lactating females can eat more than their body weight in insects daily. Little brown bats are often found near streams, ponds, and lakes because part of their diet comes from aquatic insects. Forty-four other species of bats are native to North America and are extremely important to agriculture, partially by pollinating certain crops but also by consuming night-flying insects.
Find out which bats are found in your area and consider constructing shelters for them around the orchard but away from storage buildings and other areas where people work. This separation will reduce human/bat interactions and keep the bats’ strong-smelling feces away from areas where people congregate. Note that bat populations in North America are presently threatened by a serious disease called white nose syndrome (WNS) that was first observed here in about 2006.
Even with the best cultural practices, most commercial organic fruit growers need insecticides to produce marketable crops. While relatively few organic insecticides are registered, several new materials have become available in recent years. The following materials are allowed in certified organic orchards under the U.S. National Organic Plan and are generally allowed under other certification programs. If you are a certified organic grower, be sure that the products you use are approved by your certification organization.
Use even these organic insecticides with great care and follow label directions carefully to minimize damage to beneficial organisms. Organic certification programs usually require that you use all available cultural practices to control pests before applying a pesticide, and that you document this in your orchard records.
Horticultural oils have been used to protect crops for more than 150 years, and many different types are available. They may be produced from petroleum, fish, or plants. Heavier oils are applied to dormant trees and bushes while lighter-weight oils (summer oils or superior oils) can be applied to foliage and fruit during the growing season.
In general, oils smother pests and eggs and have been especially valuable in controlling mites and scales. Oils have also proven effective in controlling aphids, caterpillars, leafminers, and psyllids. Highly refined petroleum oil has proven very effective in controlling powdery mildew on cherries and peaches. Be sure that the product you use is certified for organic production and labeled for your crop.
Oils can be phytotoxic, particularly when applied with sulfur. Avoid applying oils when the humidity is high and temperatures are above 80°F (27°C). Use large volumes of water (200 gallons per acre or more), and set your sprayer equipment to produce fine droplets. Make sure the oil has an emulsifier to allow it to mix with water, use constant agitation when spraying, and follow label directions very carefully.
Horticultural oils are generally safe for mammals and birds when used carefully and according to label directions. They can be toxic to beneficial mites and result in pest mite outbreaks when used incorrectly. In an orchard, an application of dormant crop oil just as buds swell in spring is very effective in controlling mites and scales when the beneficial organisms are not yet in the trees. To avoid phytotoxicity, be careful not to apply too soon before or after sulfur sprays.
Insecticidal soaps are made from potassium or ammonium salts of fatty acids and are applied to plants to control insect and mite pests. The soaps act by smothering pests or damaging their cuticles (outer layers) and allowing the pests to dry up and die.
Insecticidal soaps work best against small, soft-bodied insects like aphids, mealybugs, thrips, whiteflies, and mites. Soaps are also toxic to caterpillars and leafhoppers but generally do not provide an effective level of control against them, especially against older, larger larvae. These products have little impact on hard-bodied insects, including pest and beneficial beetles and syrphid flies, and do not usually harm bumblebees. They have a very low level of toxicity to mammals and birds, although the soaps are irritating to the skin and eyes. Ammonium-based soaps are sometimes touted as being repellent to deer and rabbits, but do not count on them to protect your trees or bushes against these pests.
Although pesticidal soaps are very useful, they have definite limitations and must be used as part of a system that integrates other pest controls. Their effectiveness is rather low, perhaps 40 to 50 percent, against small, soft-bodied pests. Soaps kill only pests that are contacted directly by the soap solution and in relatively large amounts. Once the soap solution dries on the plant, it has no effect on pests. You need to spray thoroughly to ensure the upper and lower surfaces of branches, leaves, and fruits are covered. This means using large amounts of soap solution, usually at about 2 percent concentrations.
Hard water makes soaps ineffective. If your water is hard, you may need to treat the water to soften it. Some products are available that can be added directly to the water to improve insecticidal soap effectiveness. Follow label directions carefully. Soap sprays work best when they dry slowly, such as on cool, cloudy days, or in the evening.
The soaps can be phytotoxic if used too frequently or at concentrations that are too great. Similar soap products have been developed as organic herbicides, as we discussed in chapter 9 (see page 297). Fruit crops generally tolerate pesticidal soap applications well, but fruit can be damaged if large amounts of spray collect at the bottoms of fruits. Soaps are also highly unpalatable and have offensive odors. Be sure your fruits are free of soap residue before using or marketing them.
Microbial insecticides include assorted strains of Bacillus thuringiensis and Beauveria bassiana.
Bacillus thuringiensis (Bt) is found naturally in soil and on plants, and many different subspecies or strains exist, some of which attack insects. It is very important to know that not all strains attack all insects. Some strains are effective against caterpillars (moth and butterfly), while others attack beetles or whiteflies. These products are generally nontoxic to mammals or birds, although a very small percentage of people are allergic to B. thuringiensis in large concentrations, and the bacteria can enter the human body through wounds or contact with mucous membranes.
Bacillus thuringiensis products work only after an insect ingests them. A crystalline protein produced by the bacteria attaches to the gut of the insect, perforating the gut wall. The insects often stop feeding rather quickly after ingesting the bacterium but may take several more days to die. Bacillus thuringiensis products have a short lifespan in orchards and typically do not remain effective for more than a few days after being applied to crops. Be sure that the product you use is certified for organic programs (there are some genetically engineered Bt products available), and be sure your product is labeled for the specific pest you are trying to control. Resistance to B. thuringiensis has been found in some populations of diamondback moth and Colorado potato beetle, probably due to overuse of these bacterial insecticides. Use Bt products in rotation with other pesticides in an integrated and diverse pest management program.
Beauveria bassiana is a soilborne fungus that is found worldwide and that attacks some insects. Two strains are commonly used to control pests and are made using fermentation to produce spores that are applied to plants in sprays.
Pests for which B. bassiana products are registered include ants, aphids, caterpillars, grasshoppers, mealybugs, thrips, weevils, and whiteflies. Infection usually occurs when the spray contacts an insect or the insect contacts the spores left on plant surfaces after the spray dries. The spores germinate on the host body and penetrate the cuticle, killing the pest in 3 to 5 days. The infected bodies produce more spores that can infect additional pests.
Beauveria bassiana products work best in cool, cloudy, moist conditions at temperatures below about 80°F (27°C). They are likely to be of more use to growers in moderate climates than in warmer regions. Apply the product only when the pest is present, and target young pests early in an infestation. The effectiveness of B. bassiana products has been variable, with more research studies showing poor pest control than showing fair or good control. Beauveria bassiana does not discriminate against pests and beneficials. Avoid spraying B. bassiana products when pollinators are active in your fruit crops.
Spinosad is a patented product that is derived from the fermentation of the very rare actinomycete bacterium Saccharopolysora spinosa. This product is a broad-spectrum pesticide that is useful against many insects. The material works mostly as an ingested poison, although insects directly contacted by the spray can also be affected. Essentially, the toxin causes the nervous system to maintain a high state of agitation until the insect dies from exhaustion.
Spinosad has very low levels of toxicity for mammals, is slightly toxic to birds, and is highly toxic to bees. Spinosad persists for several days on leaf and fruit surfaces and is most effective against caterpillars and beetles that feed on the leaves. Its control of aphids, whiteflies, and thrips has been mixed. Beneficials are generally not affected much by the material once the spray has dried.
Spinosad can persist for months in water and soil that is not exposed to sunlight. It is moderately toxic to fish and aquatic invertebrates and should not be allowed to contaminate surface waters. While spinosad is a breakthrough for controlling leaf rollers and other orchard caterpillars and plant-eating beetles, it is not a silver bullet. Resistance can build up when the material is overused, so make it part of an integrated program, and rotate it with other pesticides such as neem products and Bacillus thuringiensis. Several commercial products containing spinosad are available. Ensure the products you use are registered for your crops, pests, and area.
Neem products are derived from seeds of the neem tree, Azadirachta indica, as discussed in chapter 10. Neem products have been used as pesticides for centuries, although serious research on them only began in the 1920s in India and spread to other countries in about 1959. There are three basic types of neem products: azadirachtin-based, neem oils, and neem oil soaps.
Neem oil is produced by crushing the seeds and extracting active ingredients using water or alcohol. The extraction and processing methods that are used affect the oil’s effectiveness as a pesticide, meaning not all neem products are created equal. Although azadirachtin was thought to be the primary pesticidal compound, it now appears likely that other chemicals in the neem seeds also help protect crops. These compounds act like hormones in insects, preventing juveniles from maturing into adults. They also reduce insect feeding and egg-laying on treated plants.
In fruit crops, neem products have effectively controlled aphids (including rosy apple and wooly apple aphids), leafhoppers, spotted tentiform leafminer, and tarnished plant bug. It has partially controlled white apple leafhopper, caterpillars, and mites. It has not performed well against beetles, psyllids, and scales. Mixing azadirachtin-based and neem oil products has sometimes produced better results than using the materials alone. Mixing neem oil and neem oil soap products can cause phytotoxicity.
Pyrethrum products are derived from the dried flower heads of several species of pyrethrum daisies. They are effective against a wide range of insects and paralyze the insects by attacking their nervous systems. Pyrethrums are especially known for knocking down insects quickly. Unfortunately, the insects are not killed quickly and can recover from the paralysis if the pyrethrum dose is too low.
Pyrethrums are also quickly broken down by sunlight, water, and soil, meaning they have very short life spans in an orchard. To be effective, the spray must actually contact the pest. Synthetic pyrethroids have a much longer active period and are more effective pesticides but cannot be used in organic programs. Many pyrethrum products are on the market. Be sure you purchase those approved for organic use. Pyrethrum has provided fair to good control against green peach aphid and good control of western grape leafhopper but poor control of other orchard pests in limited tests.
Surround represents a breakthrough approach to pest management called particle film technology. It is not, however, a silver bullet and must be used as part of an integrated system. Made from an edible clay (kaolin) that is used in processed foods, toothpaste, cosmetics, medications, porcelain, and paper, this material is also valuable in orchard pest and disease management. The product consists of very finely ground kaolin clay that is applied to orchard crops as a spray, with the wettable powder suspended in water. Once dry, the kaolin forms a thin, white film over the leaves, fruit, and wood. Although nontoxic, the film prevents some pests from recognizing the host plants. Other pests appear to be repelled by the film. Note that Surround is a special formulation of kaolin. Simply spraying raw kaolin on fruit trees can, reportedly, damage or kill them.
Surround has reportedly done a good job of controlling leaf rollers and leafhoppers and has partially controlled apple maggot, codling moth, plum curculio, thrips, and stinkbugs. Weekly sprays usually begin at petal fall and continue for about 8 weeks. Prebloom sprays are also useful in managing several pests, as discussed later in this chapter. The kaolin is not applied during bloom. If necessary, the sprays can be continued until harvest, although the fruits must then be washed to remove the white film. During the growing season, the film washes and rubs off the trees, making it necessary to apply it frequently in wet and windy climates. Fruit specialists in high-rainfall areas of the southeastern United States report problems keeping enough kaolin on the trees to be effective in controlling pests.
The added benefits of Surround include improved photosynthesis (probably by deflecting sunlight and cooling the leaves) and improved coloring on some apples. The kaolin film appears to reduce symptoms of fire blight, sooty blotch, and flyspeck. It is compatible with most organic pesticides, but do not tank-mix it with sulfur or Bordeaux mix.
Many insects and mites feed on orchard crops. Most cause minor damage and are easily controlled. In order to develop an effective pest management program, you need to know which pests are found in your area. As for diseases, Cooperative Extension and Ministry of Agriculture offices often publish regional guides for fruit growers. Many of these guides are now available on the Internet for regions across the United States and Canada. The following section includes the more serious and common orchard pests found in North America.
Sucking pests include insects and mites that feed directly on the liquid contents of leaf and fruit cells. Typical orchard sucking pests include aphids, leafhoppers, scales, and mites. Because they feed on sap from inside the cells, ingestion-type insecticides are generally ineffective in controlling these pests. Beneficial organisms play important roles in controlling many sucking pests.
In North America, the most common and serious aphid pests include:
Aphids are among the most common horticultural pests and affect an enormous range of plants, including orchard crops. Of the more than 4,000 known aphid species, about 250 attack agricultural crops and at least 12 can cause moderate to serious damage to pome and stone fruits in North America. All are soft-bodied insects that feed by sucking the phloem contents out of leaves, young shoots, developing fruits, and other tender tissues. Some aphids also feed on plant roots. Feeding causes leaves, young fruit, and sometimes shoots to become deformed. Leaves curl up around the aphids, making them hard to reach with pesticides.
The aphids excrete honeydew that covers leaves and fruits with a sticky coat and often becomes black as sooty mold grows on the honeydew. The aphids’ feeding weakens the trees and makes the crops more susceptible to other pests and diseases. Aphids also serve as disease vectors and can infect orchard crops with viruses.
Being soft-bodied, aphids are relatively easy to control, but they need to be managed with diligence and accurate timing to prevent large populations from building up. The key is to manage the aphids from the start of the growing season, before the crop is damaged. Start by applying horticultural oils (usually heavier, dormant oil formulations) at the beginning of bud swell through the emergence of green tips on the buds. Follow up, if necessary, with a pesticide as new leaves and flowers emerge. Neem products, insecticidal soaps, and Surround are often recommended to control aphids. Surround is applied after petal fall to control aphids. The timing of the sprays will depend on the pest and the product used. Follow label directions carefully. Aphids have many natural enemies, including ladybird beetles and green lacewings. Protect these beneficials and provide habitats for them in your orchard by planting insectary crops.
Apple mealybug, Comstock mealybug, and grape mealybug somewhat resemble aphids in size and habit. They have sucking mouthparts and feed on juices from the phloem, causing stippling of the leaves. Although heavy infestations can weaken trees, the economic damage comes from the mealybug’s excretions, which drip onto the fruits, creating russetted patches. The pests can also enter into the calyx ends of fruits, infecting the fruits with rot pathogens.
The pests overwinter as eggs or larvae on host plants or litter on the orchard floor. All pome and stone fruits can be attacked, as well as many other species of plants. You can use aphid control programs to effectively combat mealybugs. Parasites and predators are important parts of the management program.
Several species of leafhoppers, including potato leafhopper, rose leafhopper, and white apple leafhopper, attack pome and stone fruit crops. Leafhoppers are small, wedge-shaped insects about 1⁄8 inch long with sweptback wings. They have sucking mouthparts like aphids but are much more mobile. Although they feed only on the leaves, they damage fruit by depositing their feces on them. These deposits create spots on the fruit resembling tobacco juice and support the growth of sooty mold. A far more serious impact is that some leafhoppers vector plant diseases such as fire blight, plum leaf scald, and assorted viruses. Large infestations of leafhoppers create clouds of insects in orchards and are irritating for orchard workers. Leafhoppers are found across North America.
Programs that control aphids also work well for leafhoppers. It is very important to implement control programs early, before bloom, to prevent populations from building. Eggs are deposited on the host plant in cracks in the bark. The first larvae begin emerging at about the time of bloom. Applying dormant-type horticultural oil sprays at the beginning of bud swell through green tip may help smother eggs. Because these are sucking insects, ingestion-type pesticides have little effect on them. Azadirachtin products, insecticidal soap, and Surround appear to offer the best controls during the growing season.
Many mite pests infest pome and stone fruits in North America (see box on page 390). Spider mites feed on phloem juices and cause leaf stippling and defoliation that weaken the trees. Eriophyid mites are very small and cause similar symptoms to those of spider mites, but some can also cause leaves to become deformed and develop blisters, galls, and velvety or discolored areas. Feeding on flower clusters early in the season can also cause fruit deformities. Otherwise, healthy trees can support large mite populations without serious harm.
In well-managed organic orchards, predators usually control pest mite populations effectively. Serious mite outbreaks are often caused by pesticide programs that kill off predators, including predatory mites. It is important to make dormant applications of lime sulfur 30 days or more before bud swell and applications of horticultural oil during bud swell through green tip. At those times, predatory mites are generally not in the trees and are not harmed by the pesticides. During the growing season, sulfur fungicides will reduce mite populations. Here, however, is one of the serious weaknesses in organic orchard pest and disease management. The sulfur applications needed to control serious fungal diseases are also toxic to beneficial predatory mites. The overuse of sulfur fungicides during the growing season can lead to outbreaks of pest mites. As you develop a pest and disease management plan for your orchard, use as many strategies as you can to reduce the number of sulfur sprays applied to the trees during the growing season.
Pear psylla. This serious pest was introduced into North America. The psylla resembles a small cicada about 1/10 inch long or less and ranging from greenish-brown to very dark, depending on the time of year. Adults overwinter in bark crevices or on fallen leaves and emerge before bud break to lay eggs at the base of buds.
The larvae hatch in 2 to 5 weeks and begin feeding on leaves and buds, sucking the juices from the phloem. These larvae pass through a series of five stages (instars) in 30 to 50 days, and there may be three to five overlapping generations per year, depending on the length of the growing season. The psylla’s feeding weakens the pear trees, but far more serious damage is done by the virus-like pathogen (phytoplasma) carried by the psylla. This pathogen causes pear decline (see page 348). The psylla also injects substances into the pear trees that cause shock and damage to the trees, and the honeydew the psylla excretes contaminates the fruits and supports the growth of sooty mold.
Fortunately, it is relatively easy to manage pear psylla. Many predators and parasites attack pear psylla, including adult and larvae ladybird beetles (ladybugs), green lacewings, plant bugs, minute pirate bugs, earwigs, and parasitic wasps. It is very important to maintain healthy and abundant populations of these beneficial insects in the orchard. However, predator and parasite populations typically build too slowly in the spring to provide the control that is necessary to prevent large summer populations of psylla. Instead, you can make dormant applications of lime sulfur 30 days or more before bud swell, followed by an application of horticultural oil during bud swell through green tip to very effectively reduce psylla populations. Applying Surround pre- and postbloom, as well as azadirachtin products during and after bloom, should provide good control of this pest, provided you have an effective population of predators and parasites. You may increase the effectiveness of azadirachtin by tank-mixing it with summer-weight horticultural oil. Be careful, however, because some pear cultivars can be damaged by azadirachtin products.
Eriophyid mites include:
Spider mites include:
Many moth (lepidopterous) pests attack pome and stone fruit crops, typically feeding on leaves, fruits, and/or twigs and trunks. Some, such as codling moth, can cause severe crop loss and require aggressive management.
Codling moth is one of the most serious fruit tree pests across North America and has limited organic fruit production in many areas. The adults are brownish-gray moths with a wingspan of about 3⁄4 inch and bronze bands on the wing tips. The juveniles are pinkish-white, worm-like larvae that tunnel in and around the fruit core. This pest typically produces two generations per year. Codling moth is the proverbial worm in the apple. Even a small percentage of moth-damaged fruit can render a crop unmarketable, and it is critical to aggressively manage this pest.
Organophosphate pesticides were long the primary means of controlling codling moth. Today we use pheromone-baited traps to monitor populations and pheromone-impregnated plastic strips tied in the trees to disrupt mating. These strategies are integrated with applications of insecticides and Surround to provide organic control.
To monitor flights, attach codling moth traps impregnated with pheromone baits to branches in the top third of your orchard canopy. If more than five moths are captured during the first generation, or two moths are captured per trap in the second generation, you should apply an insecticide.
By the time the first flower buds show white or pink color (first pink), you should have 200 to 400 mating disruption dispensers per acre in your trees. These dispensers (often resembling twist ties) are impregnated with a pheromone that mimics the one produced by female moths ready to mate. The large numbers of mating disruptor strips attract the male moths and make it difficult for the males to locate females. Bear in mind that these dispensers will attract moths to your orchard and can increase damage to your crop if you have a badly infested orchard nearby.
Beginning at first bloom, apply an approved organic product containing codling moth granulosis virus. This is a naturally occurring organism that is very specific for codling moth. Repeat sprays of the granulosis virus every 7 to 10 days as long as adult moths are present. The spray will kill the larvae, but not until some damage has occurred. Beginning at petal fall, begin applying Surround, neem products, and spinosad products according to label directions as long as the pheromone traps are capturing adult codling moths.
You can also use parasites to manage codling moth populations (see the Oriental fruit moth section below). Maintain insectary crops in your orchard. Purchase and release the parasites, if needed.
During the 1960s, fruit researchers in California tested ultraviolet (black light) traps to monitor codling moth flights. The light traps were hung in the orchards just before the codling moth flights were expected to begin and turned on at dusk. In addition to codling moths, the traps caught other orchard moth pests and other insects, averaging 80 other insects for each codling moth trapped. These traps can be used to supplement the management program described above. They will not be as accurate a monitoring device as pheromone traps, and it is unlikely that they will provide adequate control of codling moth populations by themselves. To reduce their impact on non-pest insects, use pheromone traps to monitor codling moth flights and turn on the black lights only when the moths are flying.
To target pupating larvae, loosely wrap strips of cardboard around the tree trunks beginning with the spring flight. Larvae that crawl down the trunks seeking a place to pupate hide under the cardboard and spin cocoons. Examine the cardboard strips weekly after you observe moth flights and replace as necessary to destroy the cocoons.
Oriental fruit moth is an introduced pest that can cause very serious damage in fruit crops and is considered more difficult to control than apple maggot. It was once considered to be primarily a problem on peaches, but it also attacks apricots, nectarines, almonds, apples, quince, pears, plums, and cherries, as well as many woody ornamental plants. The adults are brownish to greenish moths with a wingspan of about 1⁄2 inch. They lay eggs on tender, young shoot tips, and the larvae bore into and feed on the tips. The feeding kills the twigs and shoot tips, causing the fruit trees to have a bushy appearance. The larvae also feed on young fruit (young injury) and nearly ripe fruit (old injury). Damage from both young and old injuries is clearly visible. In “concealed injury,” which is common in peaches, the outside of the fruit may appear perfect but conceal a larvae feeding within, usually near the pit.
The methods of control used for Oriental fruit moth are similar to those used for codling moth, with slight exceptions due to the fact that OFM produces three generations per year. Pheromones are available for monitoring populations, and studies of mating disruption are now being conducted. As with codling moth, Oriental fruit moth is susceptible to beneficial parasites. According to Michigan State University, Trichogramma minutum (an egg parasite) and Macrocentrus ancylivorus (a larval parasite) may parasitize 50 to 90 percent of Oriental fruit moth eggs or larvae in an orchard. The parasites alone, however, do not provide sufficient control for commercial crops and must be included in integrated pest management programs.
A number of pests fall under the category of cutworms, including Bertha armyworm, spotted cutworm, and variegated cutworm. These lepidopterous pests are night-flying moths that overwinter as pupae in the soil and emerge in early spring. The larvae range from 1⁄4 to 1 inch in length and curl up when disturbed. They feed on foliage and fruit at night. It is important to use predators and parasites to control cutworm populations, but sporadic outbreaks of the pests can occur. Codling moth management programs should also control these pests. Insecticides of choice include neem products, Bacillus thuringiensis, and spinosad products.
Eyespotted bud moth is a minor pest for apple, cherry, pear, and plum trees. The adults are small, brown moths, and the larvae are small, brown caterpillars that feed in buds, twigs, unfolding leaves, and young fruits. The leaves may be folded over. It is not usually necessary to control them, but this pest will be controlled by codling moth and Oriental fruit moth programs.
Many similar pests fall under the category of fruit worms (see box on page 394). Although they are different species, they are all moth (lepidopterous) pests that are biologically similar and can be controlled with the same practices. Some of these pests overwinter as eggs and others as mature larvae. Feeding begins as early as prebloom and can result in deeply scarred fruit. The most common symptoms include partially eaten and rolled leaves and larvae feeding on and in the fruits. Programs to control codling moth should also control most fruitworms and leaf rollers. Bacillus thuringiensis, spinosad products, and Surround are all important parts of a control program.
Gypsy moths are introduced lepidopterous pests from Europe and Asia and are slowly moving across North America. Because they can defoliate large expanses of hardwood plants, they are closely monitored by state, provincial, and federal organizations. Aggressive community and regional eradication efforts are often used when new populations are detected. Practices that control codling moth, Oriental fruit moth, leaf rollers, and fruitworms will also control gypsy moths. Tanglefoot sticky wraps placed around the trunk can help prevent the night-feeding larvae from reentering the trees. During heavy infestations, however, the larvae remain in the trees feeding around the clock. Pheromone traps for monitoring gypsy moth and mating disruption materials are available but should not be needed in most areas.
Western tent caterpillars and forest tent caterpillars can become problems in orchards, and their combined ranges spread across the United States and Canada. These pests form conspicuous, web-like nests in trees, and the larvae can quickly defoliate an orchard tree. Remove and destroy the tents whenever you find them. Programs to control other lepidopterous pests will also control tentworms.
The small, reddish-brown apple and thorn skeletonizer moth has a wingspan of less than 1⁄2 inch and is found from Virginia to California and north into Canada. The adults overwinter in bark cracks and crevices of the trees, emerging in spring and laying eggs on the undersides of leaves. Although its preferred host is the apple tree, this pest also attacks hawthorn, pear, cherry, and plum trees. The larvae are about 1⁄2 inch long, yellowish-green caterpillars with black spots. They can often be found dangling from silken threads from infested trees and blow readily from one tree to another. The larvae feed on the leaf tissues between the veins, creating a skeletonized or lace-like appearance. They roll the leaves and pupate within the shelter, emerging as adults to start a new generation.
Severe infestations of apple and thorn skeletonizer can virtually defoliate the trees, and infestations are most serious following mild winters. In most fruit-growing regions, expect at least two generations per year. Spinosad and Bacillus thuringiensis products are effective against apple and thorn skeletonizer, and rotating between these two products will help reduce resistance buildup. Neem products should provide partial control, and applications of Surround may reduce feeding and egg-laying.
At least three species of leafminers infest pome and stone fruit crops across the United States and Canada, including apple blotch leafminer, spotted leafminer, and western tentiform leafminer. These pests are small moths about 1/10 inch long. Adults have brownish wings with white bands that appear silvery as the moths fly.
The adults deposit eggs on the undersides of the leaves, and the larvae tunnel into the centers of the leaves and tunnel through the leaf between the upper and lower surfaces. The first three stages (instars) of the larvae have sucking mouthparts, and the fourth and fifth stages have chewing mouthparts and eat the leaf tissues. The later larval stages web together the sides of the tunnels, creating tent-like shapes. The larvae then pupate inside the fallen leaves, emerging as adults in early spring as new leaves begin unfolding.
Parasites normally control these pests, and serious outbreaks are infrequent. During mid-spring, examine 100 leaves per block of trees. If there are fewer than two or three tunnels per leaf, you probably do not need to control them. If there are more than two or three tunnels, you may want to begin a management program. Applying azadirachtin products, insecticidal soaps, and spinosad products just before bloom should help manage leafminers. Good sanitation practices that involve removing or destroying overwintering leaves on the orchard floor may also help reduce leafminer populations.
Several fly, sawfly, and midge insects are serious pests on fruit crops. Among the most serious are apple maggot and various fruit flies. While damage to the fruit may often appear minor, even a small percentage of infested fruit can render a fruit shipment unmarketable.
One of the most widespread and serious fruit pests in North America, apple maggot has long limited organic production. This insect primarily attacks apple trees, but it also infests cherry, crab apple, hawthorn, pear, plum, and quince trees. Adults are black flies that are a bit smaller than houseflies and have black bands on their wings. They emerge from the soil in spring to lay eggs under the fruit skins. The eggs hatch into small, white larvae that tunnel throughout the fruits, eventually dropping to the ground and forming pupae that overwinter. There is only one generation per year. Maggot-damaged fruit is unmarketable and usually unsuitable for home use.
Control starts with early detection. Adult flights can be detected and monitored using yellow sticky traps or red sticky spheres hung in your trees at about eye level. Unfortunately, the traps do not capture enough flies to manage the population. In western North America, the adults start laying eggs about 10 days after they begin flying. Applying Surround, beginning at petal fall, will somewhat control apple maggot. Spinosad significantly reduced maggot damage on apple trees in Cornell tests. Begin these applications at petal fall.
The most serious fruit flies for stone fruit growers are cherry fruit flies, of which there are several species ranging across North America. Fruits damaged by maggots are unusable, and maggots in processed cherries are considered contaminants. The real problem is for commercial growers because there is a zero tolerance policy for maggots in packed fruit. A single larva found in a shipment will cause that shipment to be refused. In the Pacific Northwest, the western cherry fruit fly is the primary commercial cherry pest and requires perfect control. Spotted-wing drosophila was recently introduced into California and is considered an extremely serious emerging pest of cherries, raspberries, strawberries, blueberries, and perhaps of other stone fruits because of similar quarantine issues.
Adult cherry fruit flies resemble small houseflies, and the larvae are white maggots that feed inside the cherries. The pest overwinters as pupae in the top 4 inches of the soil. It emerges beginning about five weeks before harvest, and peak emergence is generally about harvest time. The adults spend 5 to 10 days feeding before laying eggs under the skins of the fruit. After feeding inside the fruits, the larvae drop to the ground, tunnel in, and pupate until the following year. The fruit flies usually remain very close to where they emerge. Using effective control measures within an area will generally reduce or eliminate the pest until it is reintroduced. An important control measure is to eliminate all wild and escaped cherries in and around your orchard.
To date, biological controls do not provide the perfect control needed for commercial fruit. Yellow sticky traps and sticky red spheres can help monitor the pests, but results are poor to variable. According to Washington State University, cherry fruit flies do not respond to attractant pheromones.
Early-maturing cherries are least susceptible to these pests. Pick all fruit from the trees, as even a few remaining fruits can support a new generation of flies. Harvest fruit as soon as it is ripe, and destroy dropped and culled fruits. Surround provides some protection, and spinosad-impregnated baits splattered in the trees have provided at least partial control of adults before they can lay eggs. Spinosad also appears to be effective against spotted-wing drosophila. At least two sprays are required, the first just as the fruits are turning pink and the second 7 to 10 days later.
The European apple sawfly is an introduced pest that is now found in the northeastern United States and Ontario. The adult flies are 1⁄4 to 1⁄3 inch long with yellow heads, nearly black backs, and yellow to orange lower abdomens. They emerge from cocoons several inches below the soil surface at just about apple bloom time. The females deposit their eggs in apple blossoms, and the resulting larvae feed near the surface on developing fruits, causing prominent scars that make the fruit unmarketable. In later feeding, the larvae tunnel toward the core of the fruit. A single larva can damage all the fruits in a cluster.
Mature larvae grow to about ⅜ inch long and resemble caterpillars. Sawfly larvae can be distinguished from caterpillars by having seven pairs of prolegs (stumpy leg-like appendages) rather than five. Damaged fruits often drop about the time of normal June drop. The larvae emerge from the fruits, tunnel into the soil, and pupate until the following spring. Although two generations per year occur in Europe, normally only one generation per year occurs in North America. So far, parasites and predators have not effectively controlled European apple sawfly. You can monitor populations of this pest by hanging white sticky cards in your trees.
Although the larvae look like caterpillars, they are not affected by Bacillus thuringiensis. The best organic control appears to be two prebloom applications of Surround, followed by an insecticide spray at petal fall. Be very cautious. Pesticides that control these pests also kill bees. Programs that control spring-feeding moth larvae and tentiform leafminer should also help control European sawfly. There have been very few published recommendations on how to control European sawfly with organic methods. Neem and spinosad products appear to be the most likely candidates to treat the pests at petal fall.
Also called pear slug and pear sawfly, cherry slug is widespread across North America. It is easily controlled and usually causes only minor damage, but it can be serious in poorly managed orchards and on young trees. The adults are shiny black flies that are 1⁄4 inch to nearly 1⁄2 inch long. They emerge from the soil in early spring and lay eggs in slits they make on the leaves of cherry and pear trees.
The eggs hatch into slime-covered, olive-green larvae that feed on the upper surfaces of the leaves, skeletonizing them. The larvae drop to the ground, pupate several inches below the soil surface, and emerge as new adults during July and August. Heavy feeding can weaken the trees; insecticidal soap, spinosad products, and Surround should provide good control.
Pear leafcurling midge is an introduced European pest that attacks only pear trees. The adults are tiny flies that pupate underground and emerge at about bloom time and lay their eggs on new, folded leaves. The grub-like larvae hatch in 3 to 5 days and feed within the folded leaves, with as many as 30 grubs per leaf. The feeding causes the leaves to remain tightly folded, protecting the grubs from predators.
When they mature, the grubs chew out of the leaves, fall to the ground, and pupate. Depending on the growing region, you may experience four to five or more generations per year. Mature trees tolerate the damage, and control is seldom needed in established orchards. Newly planted pear trees in orchards and nursery trees can be severely stunted. In conventional orchards, organophosphate pesticides are used to control the pest, but recommendations for organic control in North America are lacking. In New Zealand, the closely related apple leafcurling midge is effectively controlled by parasitic wasps, pirate bugs, and earwigs. Where the midge is a problem, consider applications of neem and spinosad products at petal fall and focus on maintaining healthy populations of beneficial insects.
Many insect pests damage fruit trees by boring into trunks, branches, and twigs, including ambrosia beetle, American plum borer, dogwood borer, lesser peachtree borer, Pacific flatheaded borer, peachtree borer, peach twig borer, and shothole borer.
These are general terms that include species that range from the southeastern United States to the Pacific Northwest and into Canada. Other names include fruit-tree bark beetle, lesser shothole borer, European ambrosia beetle, and Asian ambrosia beetle. These pests were introduced from Europe and Asia and are serious pests of forest, fruit, nursery, and landscape trees. The adults are small, dark brown to black beetles with hard bodies. They bore into trunks and stems, creating multiple-chambered tunnels or galleries in the inner bark and outer sapwood.
The adults lay eggs in the galleries, and both adults and young inhabit the tunnels, feeding on ambrosia fungus that is cultured and tended by the adults. The larvae typically pupate in the tunnels and emerge as adults by boring a hole out through the bark. The many entry and exit holes produce the characteristic shothole effect. The tunnels damage the phloem and weaken the trees, and the ambrosia fungus can block the vessels that carry water and food. Fusarium and other pathogens can also be introduced into trees. There are no effective chemical controls for organic fruit growers. The best strategy appears to be keeping your trees healthy because these pests sometimes prefer to target weakened trees.
The larvae of this reddish-brown or coppery beetle bore beneath the bark and can girdle the trees. Apples, cherries, plums, and other stone and pome fruits are hosts of this borer. Young trees are at greatest risk of girdling, and the adults target sunburned or otherwise damaged areas of the trunks. There are no recommended organic chemical controls. Wrapping the tree trunks and shading them with boards may help prevent sunburn and make the trees less attractive to adults. Applying Surround should also help reduce sunburn.
Peachtree borer and lesser peachtree borer are common pests across North America, particularly east of the Rocky Mountains. The peachtree borer adult is a steel blue moth, and the females have a distinctive orange band around their abdomens. Besides peaches, these borers attack cherries, plums, prunes, nectarines, and apricots. They overwinter as mature larvae in tunnels near the soil surface. The larvae pupate on the soil surface and emerge as adults, typically from June to September. The adults lay eggs singly or in masses near the soil line, and the young tunnel into the trunk and large roots near the soil surface.
Young trees can be girdled or killed by a single larva, and older trees can be damaged. Mounds of sawdust-like frass and small holes, often with gummy exudates near the soil line, indicate that the pests are present. You can protect trunks by tightly wrapping them with plastic or metal that extends several inches into the soil and fits tightly against the trunk for several inches above the soil. Heavy-duty aluminum foil works well for this purpose. For small plantings, excavate about 3 inches into the soil around the trunks and kill individual larvae using a wire to probe into the feeding holes.
To reduce egg laying and feeding in the Pacific Northwest, horticulturists recommend applying Surround to the base of trees in early spring. Making weekly applications of Bacillus thuringiensis to the base of the trees from July through August can kill the larvae as they begin feeding on the trunks. The parasitic nematode Steinernema carpocapsae can help manage these borers when applied as a drench to the lower trunks and soil during warm weather in spring and fall. You can also use mating disruption twist ties (Isomate) to manage pest populations.
Peachtwig borer is an introduced moth pest that attacks twigs, shoot tips, and newly emerging shoots of peaches, plums, and apricots. The pest overwinters in limb crotches inside chimney-like structures called hibernacula, which are made up of sawdust-like frass. The larvae emerge early in spring and begin feeding on newly emerging shoots before pupating in protected areas on the trunk or inside fruits.
The adults emerge to lay eggs on new shoots, fruits, and young branches, and there are multiple generations each year. Later generations of larvae feed inside the fruits, usually entering near the stem. Applying dormant lime sulfur 30 days or more before bud swell and dormant horticultural oil sprays at bud swell through green tip are quite effective ways of managing this pest. Spinosad can be tank-mixed with the oil. Summer Bacillus thuringiensis sprays can help manage the larvae and mating disruption strips are available. According to the National Sustainable Agricultural Information Service, “The peach twig borer has many natural enemies and parasites, including the parasitic wasps Paralitomastix varicornis, Macrocentrus ancylivorus, Euderus cushmani, Hyperteles lividus, Erynnia species and Bracon gelechiae, as well as the grain mite Pyemotes ventricosus. The California gray ant, Formica aerata, can be beneficial when it preys on peach twig borer, but it unfortunately also protects aphids and scales. Other predators of the peach twig borer include lacewings, ladybugs, and minute pirate bugs. Beneficial, predatory insects can be attracted to the orchard by habitat plantings, cover crops, and hedgerows.”
Several beetle and plant bug species are pests of fruit tree crops in North America. The most serious is plum curculio, which attacks a wide range of stone and pome fruits and has severely limited organic tree fruit production in eastern North America.
Plum curculio is an extremely serious pest of pome and stone fruits in eastern North America, roughly east of the longitude line running through Manitoba and Texas. Adults are beetles with characteristic weevil snouts. They emerge from cocoons in the soil in early spring and fly to the trees, where they feed on buds, flowers, and developing fruits. They lay eggs in developing fruits, and the female cuts a crescent-shaped slit underneath the eggs, creating a flap that prevents the eggs and larvae from being crushed by the expanding fruit cells.
The larvae tunnel through the fruits, feeding near to but not on stone fruit seeds. The larvae will feed on pome fruit seeds, but they are crushed by the expanding cells inside apples that remain on the trees. In pome fruits, plum curculios only complete their life cycles in fruits that drop prematurely. When mature, the larvae leave the fruit and enter the soil, where they pupate 1 to 2 inches below the surface. The pests overwinter as adults in litter on the orchard floor or in other protected areas. Beside the adults that overwinter in your orchard, adult plum curculios are strong fliers and can enter your orchard from nearby orchards and hedgerows.
Damage from plum curculio includes early-season feeding by adults, oviposition injuries where eggs are laid, internal injury by larvae, and late-season feeding injury by adults. All make fruit unmarketable and, in many cases, unusable for home consumption.
It has historically been very difficult for organic fruit growers to control plum curculio. Pheromone traps and mating disrupters are not yet available. Routinely disking the entire orchard floor destroys many of the fragile pupal cases, but it severely damages the soil. Chickens and geese are effective in scratching up and eating the pupae, particularly when grain seed is mixed lightly into the soil on the orchard floor, but they are generally not allowed in certified organic fruit tree orchards later than 90 days before harvest. Using Surround to reduce plum curculio has proven quite effective and is probably the strongest weapon in your arsenal to manage this pest. You must apply it very thoroughly and begin applying just before bloom, and again at petal fall. You will need to repeat applications, particularly after rain.
The Integrated Pest Management group at Michigan State University has evaluated several organic approaches to control plum curculio. In addition to Surround, which they do not recommend for cherries, they suggest using Pyganic pyrethrum insecticide. Unfortunately, this material has an effective lifespan of only about 12 hours and requires frequent applications. It is also very toxic to predators and bees, so wait until petal fall to apply pyrethrums.
The MSU group has also suggested using trap crops, in which case the center of an orchard is thoroughly sprayed with Surround to protect the trees and a few border rows are left untreated but are heavily sprayed with pyrethrum. Reportedly, ‘Liberty’ apple is highly attractive to plum curculio and can be used as the trap crop. This push-pull approach is designed to push the adults out of the center of the orchard and pull them to the perimeter, where they can be more easily controlled and where there will be less damage to beneficial insects and mites in the main orchard. In a similar approach, called mass trapping, the orchard is sprayed with Surround. Areas outside the orchard are stocked with many plum curculio traps that collect the adults before they can reproduce.
The MSU group also reports that Beauveria bassiana fungi and Steinernema nematodes appear to be promising ways of controlling plum curculio between the spring and summer generations, when the pest is on the ground or in dropped fruit. Apply these organisms following irrigation or rain.
In home and smaller orchards, it is very important to remove dropped fruit throughout the season. In larger orchards, using hogs for controlled grazing reduced subsequent plum curculio generations three- to five-fold, according to MSU. Unfortunately, the National Organic Program requires removing livestock from the orchard at least 90 days before harvesting tree fruits. The grazing strategy might be effective with cherries, where the animals are placed in the orchard after harvest.
Japanese beetle was introduced to the eastern United States in about 1908 and has been moving westward with outbreaks across the United States and Canada. The adults are bright, iridescent beetles with coppery wings and feed on the leaves and fruits of stone and pome fruits and on a large range of other plants. The white grubs feed on the roots of trees, shrubs, turfgrasses, and other plants. There is one generation per year, and damage from adults usually appears as irregular holes on or skeletonizing of the leaves. Fruits may also be attacked.
Although pheromone traps are available, studies have shown that they attract more beetles than they catch. If you use these traps to monitor Japanese beetle populations, place the traps well away from your orchard. Most Japanese beetle control programs target the grubs. Milky spore virus and special strains of Bacillus thuringiensis are available for this purpose. The parasitic nematodes Steinernema glaseri and Hetero -rhabditis bacteriophora have proven effective in controlling the grubs.
Two wasps that are native to North America parasitize Japanese beetles. Tiphia vernalis looks like a black, winged ant and is found throughout the northwestern United States and south to North Carolina. The female wasps enter the soil and lay eggs on the grubs. The wasp larvae then consume the beetle grubs. The adult wasps feed on honeydew excreted by aphids that live almost exclusively on maple, cherry, and elm trees and peonies. Tulip poplar nectar is another important food source for adult wasps.
Istocheta aldrichi adult wasps lay eggs on the throats of adult Japanese beetles. The wasp larvae bore into the body of the beetle, killing it before it can reproduce. Aphid honeydew deposited on Japanese knotweed (Polygonum cuspida) appears to be a food source for the adult wasps. Because Japanese knotweed is a serious invasive weed, consider including benign relatives, including rhubarb, baby’s breath, carnations, and buckwheat, in your insectary crops and in-row cover crops.
These include a large number of pests such as mullein plant bug, lygus bug, western tarnished plant bug, consperse stinkbug, say stinkbug, and western boxelder bug. Although this is a large and varied group, they all damage fruit by feeding on the developing buds or young developing fruits, causing them to be deformed. Peaches may develop humpy shapes or catfacing. Other tree fruits can be deformed or have corky areas. The damage caused by plant bugs often leaves the fruits edible but unmarketable. Bugs collected with the harvested fruits can create disagreeable odors and render your fruit unusable.
Plant bugs are associated with a wide range of hosts, including blackberry, raspberry, mustard, and alfalfa. You can monitor pest populations by using an insect sweep net in your alley, in-row, and insectary cover crops. Also monitor inside your fruit trees using a beater tray.
Although no threshold numbers have been established, if you find the pests, you might want to take action, particularly early in the season between bud break and June drop. During this period, avoid harvesting or mowing alfalfa, rape, canola, or mustard crops in or around your orchard. Mowing these crops can drive the adult bugs into your trees to feed on the blossoms and fruits. During the growing season, mow alternate alleys and in-row crops at least 1 to 2 weeks apart to leave habitat on the orchard floor for the adults and reduce the numbers in your trees.
Remove wild and escaped brambles from your windbreaks and fence-rows. You can make prebloom and postbloom applications of Surround to help prevent feeding damage and use azadirachtin sprays to kill the pests in the trees. Monitor pest populations in your trees during the growing season using beater trays. If the pests are present, you may want to apply control sprays 1 and 2 weeks before harvest to reduce the contamination of harvested fruits.
The campyloma bug is rather a paradox. The young larvae resemble fast-moving, translucent, greenish-white aphids. They cause damage by feeding on developing apples less than about 1⁄2 inch in diameter. Yellow and green apples appear more susceptible to damage than red varieties. Damage appears as small corky spots on the young apples, and severe infestations can cause catfacing on the fruits.
Adults are reddish-brown, oval plant bugs with dark spots on their legs and antennae. Unlike the nymphs, the adults are beneficial insects, feeding on orchard pests. Monitor populations using a 20-inch-diameter round or 18 × 18-inch square white tray and padded stick to collect the juveniles. Hold the tray under the blooms, and strike the branches with the stick. Sample one branch per tree from at least 10 trees in each 5-acre block. If there is less than 0.1 larva per tree for yellow or green apples, and less than one insect per tree for red varieties, no treatment is needed.
If you must spray, treating at prebloom and bloom times is more effective than treating postbloom. Unfortunately, organic insecticides, other than rotenone, are not generally listed for control of this pest. Because of potential human health problems, rotenone is typically no longer available to organic fruit growers. Neem products, insecticidal soaps, and spinosad products are about the only materials available for this pest. Apply insecticides from prebloom until the first blossoms begin opening, and again at petal fall.
Scales are sucking insects that include San Jose scale, oystershell scale, and fruit lecanium scale. Unlike aphids, which are soft-bodied and easy to kill, adult scales cover themselves with hard shells that fit tightly against the bark, leaves, and fruits. Scales are common and serious pests of tree fruits across Canada and the United States. The adults’ and nymphs’ feeding weaken and can kill trees, and the scales on fruit make the fruit unmarketable.
These pests overwinter as eggs and larvae in fruit trees and many other woody hosts. It’s important to scout carefully for them. During the dormant season, look for the flattened shells on twigs and limbs. In early spring, about the time codling moth emerges, use pheromone traps to monitor the flights of male San Jose scales. From spring through fall, attach black sticky tape, with the sticky side out, around twigs and small branches to detect crawlers. It is at the crawler stage that the scales are most susceptible to predators and pesticides, but with up to five generations per year, you can almost always find the crawlers during the growing season.
A very effective way of controlling scales is to apply a dormant lime sulfur spray about 30 days before bud swell, followed by a dormant horticultural oil spray during bud swell through green tip. Using summer-weight horticultural oils during May and June can also be effective, but they may cause phytotoxicity on your fruit crops. Azadirachtin can control crawlers and mobile adults during the growing season.
These pests include pear thrip and western flower thrip. Despite their names, thrips attack a wide range of fruit hosts across North America. Thrips are tiny, about 0.05 inch long, and range from nearly black to brown to straw-colored. The adults and nymphs feed primarily on flowers and can damage and deform them. They also feed on developing fruits, causing cosmetic stippling and small scars. The late-season damage they do to cherries leaves silvery rings where the cherries touch each other.
Thrips live on flowering plants in and around the orchard. Even in a clean, well-managed orchard, these pests can fly in from surrounding areas. One effective strategy is to focus pesticide treatments on the perimeter tree fruit rows or trap crop rows. Avoid mowing or cultivating the orchard during bloom, so as not to drive more thrips into your trees. Apply azadirachtin and spinosad products beginning at petal fall. Later in the season, lacewings and pirate bugs should provide adequate control in most orchards. It may be helpful to make mid- and late-season applications of azadirachtin or spinosad products to late-maturing varieties of cherries such as ‘Lapins’ and ‘Sweetheart’.
Earwigs are minor, but common, pests in orchards and are easily recognized by the prominent pincer-like structures at the end of their abdomens. They are opportunistic, usually night, feeders, and they prey on soft-bodied insects as well as decaying vegetation. They also feed on ripening and overripe fruit, leaving shallow, irregular holes. Earwigs emit a foul-smelling liquid when alarmed and can contaminate fruit during harvest.
Control earwigs by keeping vegetation and debris away from the base of the trees and generally following good sanitation practices. Harvest ripe fruit promptly, and remove overripe and cull fruit from the orchard. Applying a sticky wrap (Tanglefoot) around the trunks can prevent adults and juveniles from climbing into the trees at night. When earwigs become a problem, spinosad products are recommended for organic control. Because they help manage aphids, psylla, and leafcurling midge early in the season, delay controlling earwigs, if needed, until a few weeks before harvest.