As with any fruit tree, the apple tree is subject to some common parasites that can readily ruin a bounty of fruit. Knowing what to look for and when are the two best defenses in controlling parasite activity before it becomes detrimental. If parasites are detected, gardeners have a number of options in treating them.
Most Common Parasites
Codling moth and apple maggots are the two most common parasites that affect apple trees. Other parasites such as aphids can also be a serious threat to apple trees if left untreated.
Signs of Parasite Activity
To detect coddling moth, look for reddish circles on the flesh of the apple. This is apparent at the beginning stage of an infestation. A more serious problem is evident by brown frass, a substance produced when the moth has developed into a caterpillar. Look for distinctive dark tracks to spot activity of apple maggots which enter the fruit through tunneling. Watch for patterns of curling leaves as signs of aphid activity.
Stages of Apple Tree Parasites
Coddling moths have a larval stage, the worm, and the adult stage, the moth. Apple maggots, too, have a larval stage as a worm and then during the pupal stage, mature into maggot flies. Aphids develop from eggs during the winter and then emerge in the spring.
Natural Control of Parasites
Using horticultural oil spray on apple trees can be an effective way of managing common parasites. The spray must be used during the spring, a tree's dormant season. Thinning fruit, by manually removing apples that show signs of infestation can also be a successful means of controlling parasites. Homemade traps are sometimes effective at capturing coddling moth.
Chemical Control of Parasites
Hanging sticky traps that contain pheromone lures are an easy way to control both apple maggots and coddling moths. Insecticides such as Permethrin and Sevin have also proven effective at treating common apple tree parasites. Like non-chemical sprays, insecticides should not be applied when apple trees are in bloom. Doing so will eliminate beneficial pollinators.