There are two primary approaches to biological control: conservation of existing natural enemies and augmentation by making releases of natural enemies. Considerable research has been done on both of these approaches for pest management in commercial orchards. Conservation biological control has been widely utilized and is very important. Augmentation biological control has been shown to be effective in many cases.
Home gardeners are often willing to invest heavily in their gardens, both to assure a bountiful and assumingly safe harvest, but also because gardening is often considered recreation and therefore worthy of some additional investment. With these thoughts in mind, the following are possible options when considering augmentation biological control in the home orchard.
Bacillus thuringiensis is certainly a proven performer. This microbial insecticide is effective against foliage and fruit feeding caterpillars such as cankerworms, tent caterpillars, fall webworms, leafrollers and fruitworms. The residual period of activity after application is very short and multiple applications may be necessary. Sprays should be timed to control young larvae. Bt will not be useful against interior-feeding caterpillars, such as leafminers or codling moth larvae once they are inside the fruit. Bt is sold under several commercial trade names and can be found in your local garden centers.
Insect parasitic nematodes are microscopic worms occurring naturally in our soils. They enter the insect, then release a bacteria which they carry in their gut. It is the bacteria that kills the insect. Insect parasitic nematodes may provide some benefit against apple insects that spend some of their life in the soil (such as plum curculio and apple maggot), but there has been little research on such applications in orchards. They are effective against the strawberry root weevil. Insect parasitic nematodes are available for purchase commercially.
Of the commercially available parasites, Trichogramma has the greatest potential. Several species are available; T. platneri is often recommended for use against tree-dwelling pests. Potential targets include codling moth and leafrollers. High release rates are necessary because the tiny parasitic wasps can rapidly disperse from release sites, a problem when trying to cover small areas. Because the egg is the target stage, releases have to be properly timed to be effective.
Green lacewings are generalist predators that will feed on many pests, including aphids, scale crawlers, spider mites and small caterpillars. It is recommended they be applied as eggs, which are the easiest stage to handle. Two or three releases during the growing season will help control many types of pests.
Mites may become problems in home orchards. Spider mites are a cool season mite and European red mites thrive in the summer heat. If these are of concern, predatory phytoseiid mites are effective predators. Typhlodromus puri is a voracious feeder and thrives in cool weather, emerging at the beginning of bloom. Amblyseius fallacis feeds all season, thriving in the heat of the summer. Release should be made shortly after the end of the blossom period.
A biological material containing the granulosis virus has been developed for control of the fruit-feeding insect codling moth. The material must be ingested by the insect to be effective.
Regrettably, there are very few options for biological control of other serious fruit-feeding insects, such as plum curculio and apple maggot. Some non-chemical methods are used for these pests, such as trapping of apple maggot. For additional information, contact your local Cooperative Extension center. If it is necessary to use broad spectrum insecticides, remember that these may interfere with the activity of predatory or parasitic insects that have been released into the orchard.
Information on our site was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.
By: Dan Mahr University of Wisconsin – Madison/December 1997 from Midwest Biological Control News, April 1997.
Updated by: Mary Concklin, IPM, University of Connecticut. 2011.
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