Basic Pest Management for Home Orchards
Growing your own fruit can be a rewarding experience that contributes to a healthy lifestyle. However, if you are new to fruit gardening, it is important to have an understanding of common fruit pests. The big three insect pests in the home orchard are codling moth (“worm” in apple and pear fruits), peach twig borer (borer in new shoot tips and fruit of peach, nectarine, and apricot), and cherry fruit fly (maggots in cherry fruits). Powdery mildew (different species attack apple and cherry), fire blight (can kill apple and pear shoots, limbs, and trees), and coryneum blight or shothole (fungus that attacks stone fruits) are the three primary disease pathogens in home orchards in Utah.
Of all the fruit pests, USU Extension receives the most inquiries about codling moth. The most effective tools for this pest are insecticides because few natural enemies attack it due to its protected life stages. The least toxic insecticides, to humans and non-target insects, include spinosad (a natural toxin produced by a bacterium), codling moth granulosis virus, and acetamiprid. Accurate timing of sprays will reap the best insect control, minimize harmful effects to beneficial insects, and save time and money. The Utah IPM Advisories (fruit, vegetable, ornamental, and turf) provide information on current pest activity and management advice throughout the growing season. You can sign up for a free subscription that alerts you when a new advisory is posted. How-to video fact sheets on the Utah Pests website provide information on homemade traps and exclusion techniques for codling moth, earwig, spotted wing drosophila, European paper wasp, and other pests.
The peach twig borer can be a major pest of peach, nectarine, and apricot along the Wasatch Front and in the St. George area of Utah. The larvae (caterpillars) of this moth overwinter in protected cells on the twigs of trees, and so the delayed dormant oil spray that covers and suffocates the larvae is a very important first step to management of this pest. The dormant oil should be applied at bud break when pink blossom tissue just begins to show, but before flowers open. An insecticide, such as permethrin, gamma-cyhalothrin, or malathion can be added to the oil to provide greater suppression of the larvae. Alternatively, sprays of Bacillus thuringiensis (Bt), a bacterial insecticide, can be applied during bloom to kill the overwintered larvae as they begin to feed on the new shoot growth. Bt is harmless to bees and other pollinators. Bt, spinosad, or acetamiprid can be applied during fruit development when summer generations of peach twig borer larvae begin to hatch.
Cherry fruits become susceptible to infestation by cherry fruit fly when their color changes from yellow to pink blush. A yellow sticky trap hung in a cherry tree can inform if and when adult fruit flies are active. The female fly inserts her sharp ovipositor just under the skin of the fruit to lay her eggs. Prevention of egg-laying is the primary strategy to prevent wormy cherries. Spinosad, carbaryl, and malathion are all effective in killing adult flies. Begin sprays when fruit is susceptible based on color, reapply insecticides based on the protection interval listed on the product label, and don’t spray too close to harvest. Use landscape fabric under the canopy of cherry trees to reduce pupation and emergence of adults from the soil. Clean up dropped fruit that may contain maggots. Chickens, ducks, and other fowl will eat maggots that drop from the fruit, and help reduce cherry fruit fly populations.
USU Extension offers numerous online publications to help diagnose and manage pests in the home orchard. The Utah Home Orchard Pest Management Guide is a comprehensive bulletin that includes an overview of integrated pest management (IPM) practices, spray tables for fruit crops, photos and descriptions of pests and natural enemies, suppliers of IPM products, and names of common home pesticides. A series of backyard orchardist fruit pest fact sheets are also available for apricot, apple, cherry, peach, pear, and plum. The USU Extension fruit website provides links to resources on home garden and commercial fruit production, including determining the hardiness zone of your location and fruit tree pruning and nutrition guidelines. Check out these home fruit production resources and contact your local Extension office for further assistance.
-Diane Alston, Entomologist