How Kootenay Covers Prevent Bug Damage

Kootenay Covers keep insects from laying eggs on or in developing fruit. The holes in the mesh are so small that adult bugs cannot get through to the fruit. No eggs on the fruit means no caterpillars or maggots infest the fruit. The fruit grows to maturity without bug damage.

Common Bugs and Your Fruit

There are several primary kinds of insects that damage fruit. This page describes these insects, how they damage the fruit and how Kootenay Covers prevents the damage.

For cherries and other kinds of stone fruit (fruits with a stone-like pit in them) there are a variety of flies that lay eggs in the skin of developing fruit. These eggs hatch as a tiny maggot or larva embedded in the fruit. The larvae tunnel through the fruit, often eating into the center of the fruit. As they feed, they make the inside of the fruit brown and mushy. Maggot-infested fruit are not enjoyable to eat.

Apples, pears and quinces, also known as pome fruit, have a collection of seeds in the center instead of a pit. Codling moths and apple maggot flies are the two common pests that damage pome fruit. The codling moth is found across North America and other areas in the world. The adult codling moth is about 1/4 of an inch long. In the spring after the apples have typically reached about 1/2 inch or larger in size, the moth hatches from pupae over wintering on bark or in the ground. The moths mate. The females then lay their eggs on leaves or fruit. The eggs hatch and a tiny caterpillar emerges. The caterpillar burrows into the green fruit. The caterpillar tunnels into the center of the apple, where it eats the young seeds.

After feeding for 2-4 weeks, the caterpillar burrows back out of the apple. It drops to the ground or finds a protected place under bark where it spins a cocoon. Inside the cocoon, the caterpillar turns into an adult moth. The adult moths then emerge from the cocoon and the cycle starts again. Depending on the local climate, this reproduction cycle can repeat 2-4 times during a single growing season. Uninterrupted, each cycle brings a large increase in the number of codling moth larvae burrowing into the apples of your tree. By the end of the season every single apple in an unprotected tree will typically have at least one worm hole.

The Kootenay Covers interrupt the cherry fly and codling moth cycles by preventing the adult insects from laying eggs on the leaves and young fruit. 

For more complete protection from the codling moth, growers will want to spray a dormant oil spray on the trunk and branches of the apple or pear tree in late winter to kill any pupae attached to the bark of the tree. The Kootenay Covers can then be installed over the trees to keep moths that emerge from cocoons on the ground or cocoons on other trees from attacking the covered trees.

Another major pest affecting apple trees primarily in the eastern United States and some parts of the western United States is the Apple Maggot Fly (Rhagoletis pomonella), also known as the railroad worm. One female fly can lay as many as 300-400 eggs. The apple maggot fly is difficult to manage with spray because the eggs are deposited inside the apple by the adult fly. Spraying the outside of the apple may not kill the egg or larvae inside the apple. However, because the adult fly is about 3 mm wide, it may not be able to penetrate the Kootenay Cover mesh. Also because the larvae over winter on the ground as opposed to on the trees, we are highly optimistic that the Kootenay Cover mesh will keep apple maggot flies out of the canopy of the tree when they emerge to lay eggs in the apples. Customer feedback from the 2021-22 seasons supports our optimism that trees covered with Kootenay Covers experience very little, if any, Apple Maggot damage. Further study and data collection are required to confirm these expectations.