PHOTO: Whitney Cranshaw/Colorado State University
May 14, 2015

Spring is an important time in the orchard. Small, developing fruits are prone to damage from several common pests. Many of these critters are best controlled with techniques employed early in the season. Here are a handful of common orchard pests and some tips for controlling them without turning to synthetic pesticides.

1. Apple Maggots

These flies lay eggs under the skin of growing apples. Hatching larvae (maggots) tunnel through the fruit, causing significant damage that may lead to rot. Although these insects are most common on apples, they also attack plums, pears and cherries.

To prevent apple maggots in orchards, hang red, spherical balls coated with a non-drying glue, such as TangleTrap, on the trees in mid-June. Use a single sphere for dwarf trees and up to six spheres on full-sized trees. These traps can be purchased from farm- and orchard-supply stores and websites. The spheres lure and trap the adult flies, which think they’re ripe apples and land to lay their eggs.

2. Codling Moths

4 Insects Hurting Your Orchard (HobbyFarms.com)

Attacking apple, pear, peach and quince, adult moths lay eggs on developing fruit and leaves. The newly hatched larvae tunnel through the fruit and are often are found near the core feeding on the seeds. Larvae then leave the fruit through a different exit hole and start the cycle again. Codling moths produce two generations in a season.

A great preventative method for home gardeners involves setting up pheromone traps to lure and capture the adults. These traps are triangular tubes with a sticky interior and a pheromone bait. Adult moths are lured to into the trap where they get stuck and die. Hang two traps per full-sized tree a few weeks before bud break. The traps will then need to be replaced in July to control the second hatch.

3. Plum Curculio

4 Insects Hurting Your Orchard (HobbyFarms.com)

This blackish-brown, snout-nosed insectfeed on plums, nectarines, peaches, cherries, apricots, and pears. Soon after bloom time, female curculios lay eggs under the skin of the immature fruit, creating crescent-shaped scars. A week later the newly hatched larvae bore through the fruit to feed, often causing the fruit to drop before it reaches maturity.

Kaolin clay products are terrific at deterring this pest. Sprayed on the fruit as a liquid, it dries to form a powdery barrier around the fruit. The dusty clay deters the adults and prevents them from laying eggs. Start spraying at petal drop and repeat every seven to 10 days for about eight applications. The trees will look a little funny coated in the white spray, but it’s well worth it. Kaolin clay-based products also work great to help deter apple maggots and codling moths.

4. Peach Tree Borers

4 Insects Hurting Your Orchard (HobbyFarms.com)

Peach tree borers are larval moths that attack peaches, plums, cherries, nectarines and apricots. Adults lay eggs on the tree’s bark in mid to late summer. The newly hatched larvae burrow under the bark, tunneling between the inner bark and the sap wood, destroying the tree’s vascular system. Larvae overwinter inside the tree, and then emerge as adults early the following summer.

Pheromone traps are useful for capturing and monitoring the adults, but the best method for controlling the borer is to carefully examine the tree’s bark for small holes and bits of sawdust in the fall. Pay particular attention to the base of the tree, up to a height of about 4 feet, as this is a favorite area for the borers. If you find an entrance hole, push a straightened paperclip into the hole as far as it will go. This will squash the borer. A species of beneficial nematodes, Steinernema carpocapsae, can also be injected into the hole using a needle-less syringe. The USDA’s Agricultural Research Service found that applications of this nematode were able to control peach-tree borers, as well as chemical applications in small field trials.



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