Pests of Apple Trees

With care, you can protect your apple trees from invasion.apple tree 1 image by Przemyslaw Koroza from Fotolia.com

Bugs attack apple trees and either damage them directly or leave them open to infection. Knowing what to look for and what to expect is an important tool in the quest to produce healthy, tasty apples without any nasty surprises. Choosing disease-resistant trees is a good first step in the fight against apple pests.

Molds

Somewhere in the gray space between animal and vegetable lie the molds, which cover apples in fuzz, ruin their skin and then creep deeper. Botrytis starts as brown spots and continues as grey, furry mold; mildew causes patches of gray powder on the shoots, flowers and leaves of apple trees. According to Garden Action, both molds are caused by too much fertilizer or too much damp and cold.

To prevent mold, don't over-water, and give the tree air by cutting away undergrowth. Remove damaged parts and burn them, and spray with copper fungicide.

Aphids suck the sap of the tree, especially when they're young and easy to bite into. Shoots and leaves become distorted and the tree is weakened. You can use chemical sprays to kill aphids, but another method is to introduce creatures, such as ladybugs, that eat these pests. You can also spray them with a solution of dish soap and water, which is less likely to contaminate the fruit than chemicals.

Woolly aphid, eriosoma lanigerum, is a bark aphid. They appear like fungus or mold, but are actually coated in a waxy covering. Squash one to see whether it behaves like a squashed bug or mold. These aphids cause lumps in the bark, which then crack and let apple canker disease in. You can spray them with alcohol or with control sprays. You can also cut the affected lumps out.

Apple sawflies, Hoplocampa testudinea, look like wasps. They lay their eggs on the flowers and maggots hatch, tunneling into the fruit's skin and scarring it with thin, ribbon-like markings. They then tunnel into the fruit, which will drop off the tree before reaching maturity. To prevent the problem, acquire a spray from the nursery and spray when most of the blossoms have fallen. You should remove and burn fallen fruit.

Apple maggots are the larvae of Rhagoletis pomonella flies. They tunnel into fruit and create dark tracks that can be seen from the outside. According to the Michigan State University Extension service, the pupae overwinter at the base of the tree. The adult flies lay eggs on the fruit in mid to late summer. You can trap the flies with sticky boards--like giant flypaper--or false apples created to catch them. You can also spray trees at the same time as adult flies emerge.

Winter moth, Operophtera brumata, drills holes into the apple tree leaves and weakens the tree. The caterpillar feeds on leaves, flowers and developing fruit; by the time you notice the holes, it's already too late because the caterpillars have burrowed into the ground to pupate. There is no real cure for these pests; you need to prevent them. Tie grease bands around the base of the tree which will catch newly-hatched females as they crawl up the tree. Keep the band clean and burn it in the late spring.

Codling moth is another fruit-burrowing pest. You'll only see the hole it makes after you cut or bite into the apple. The moth lays its eggs on the fruit in the summer and caterpillars dig in until ready to overwinter, which they do in the tree's bark. A simple pheromone trap attracts male moths and reduces the females' chance to breed and lay eggs. You can also scrape off loose bark, thus removing sanctuary for the caterpillars, and tie a burlap sack around the base. The caterpillars will nest in the sack and you can then remove it later in the year and burn it. According to the University of Colorado Extension, you can also thin out fruit and spray with pesticides such as Permethrin.