Apple trees can be both a fun and productive way to produce fruit for a family. Cultivating apple trees takes ongoing care and maintenance against many types of disease and pests. There are a few pests that attack apple trees during the growing season. These pests affect different parts of the tree and cause various types of damage. Understanding the types of pests and their significance will help in treatment and prevention.
There are a variety of apple tree pests, including aphids, apple maggots, codling moths, scale and mites. Aphids can have color variations ranging from green to yellow, brown, red or black depending on the type of aphid. The most identifiable characteristic of aphids are the cornicles protruding back from the hind legs of the insect. Groups of aphids appear on leaves or stems. Apple maggots are found on the fruit of the tree. Both maggots and codling moth lay eggs directly onto the fruit, and once the eggs hatch, the larvae burrow into the fruit to feed and grow. Wooly apple aphids are found on twigs and roots, especially near freshly pruned areas. Scales are legless insects that are identified by the mouthparts, which can be up to eight times larger than the insect itself. Scales feed on the sap of apple trees. European red mites can be found on foliage of apple trees, and these pests feed on cells of the tree such as chlorophyll.
Most apple tree pests become evident during the growing season. Heavy infestations can occur during summer when both temperatures and humidity levels are high. Pests can overwinter, such as mites, where the eggs are layered at the end of the growing season and hatch the following year. Mites may become a problem after their natural enemies, such as the codling moth, have been eliminated. Codling moths can have multiple life cycles during a single year.
Significant damage to fruit can occur if either maggots or codling moth infestations are left untreated. Maggots cause brown, trailing lines through apples, whereas codling moths cause raised red circles around bored holes. The red mite might cause russetting in fruit if the infestation becomes serious. Leaf damage can also be significant. Aphids, mites and scale may cause defoliation and dieback of twigs or branches. Affected leaves will turn bronze or brown and show signs of skeletonization over time. Apple trees can become molded, stunted or die. Other ailments such as fire blight and girdling can occur as secondary infections when trees become weak. Infections from bacteria or fungus happens once trees can no longer adequately fend off the infection. Cankers can also develop over sections of apple trees because of aphid infection and can kill parts of a tree.
Treatment of apple tree pests can take various forms depending on the type of pest. Non-herbicidal treatments such as sticky red-sphere traps are used for apple maggots. These are hung in early summer to catch the eggs. Aphids can be controlled by natural enemies such as parasitic wasps that lay eggs inside the aphid. Other natural enemies of aphids include ladybugs, lacewing and syrphid larvae that eat aphids. Ladybugs and parasitic wasps are also used to control scale. It is recommended by the extension office of the University of Rhode Island to look for ladybugs on affected trees before applying other treatments. Oil treatments and insecticidal soaps can be applied but must be done within specific time frames to catch pests during their growth phase.
Prevention is the most effective method in keeping pests away from apple trees. Removing and burning damaged fruit during the season eliminates locations for codling moths and mites to lay eggs. Sweeping and burning fallen leaves halts the potential for pests to find a way onto the apple tree. Wash tools and storage with soda and warm water annually to avoid the possibility of transferring pests to healthy trees. Keep weeds and other vegetation away from the base of the tree. This helps maintain nutrients for the tree and keeps down the ability of pests to reach the tree. Avoid using mechanical weed control methods near the tree as you can damage the trunk of the tree without visible signs of damage. Spray horticultural oils on the tree at the first sign of green growth for the season, as this eliminates scale and reduces the eggs from mites and aphids.