Published on Wednesday, 30 November -0001 00:00
Apple maggots, also known as the railroad worm, are the most destructive pests of apples grown in home orchards. The apple maggots spend the winter in the soil as pupae and begin to emerge from the soil as adult flies in July. These flies do not all appear at the same time, but continue to emerge until September, making it important to apply some type of control until harvest. Shortly after emergence, the female flies begin to lay eggs in the developing apples. These eggs hatch into cream-colored, legless maggots that feed and tunnel in the flesh of the apple. Apple maggots cause two types of injury. The first type of damage occurs around the site where the skin of the apple is pierced during the egg-laying process. The flesh of the apple stops growing at this site, resulting in a sunken, misshapen, dimpled area. The second injury occurs as the maggots tunnel through the flesh. As a result, the pulp of the apple breaks down, discolors and starts to rot. If applied before the flies are able to lay eggs, insecticides help prevent apple maggot damage. The insecticide sprays need to thoroughly cover all surfaces of the leaves and fruit to be effective. Once the female flies have laid their eggs, there is no effective management. Insecticides that will successfully control apple maggot are carbaryl (Sevin) or an all-purpose orchard spray. The most effective method of application is to apply the insecticide every 10-14 days beginning July 1. Be sure to note the interval between the last spray and when you can safely harvest the apples. Do not pick the apples sooner than the time indicated on the label. Always read pesticide labels carefully before buying and again before using these products. The label is the final authority on how you may legally use any pesticide. An alternative to insecticides is management of apple maggots by trapping the adult flies with sticky red sphere traps. You can purchase these traps in some garden stores or order them through mail-order catalogs. You can also make your own traps by using a plastic or wooden ball about three inches in diameter and colored red or black. Attach a wire to the ball and coat it with a sticky substance such as Tangle-Trap. You can also purchase a pheromone attractant to make the sticky traps more appealing to the apple maggot flies. Hang one trap for every 100 apples which amounts to about five traps for an average tree. If the traps become covered with insects or debris, clean them and reapply the Tangle-Trap. Removing the sticky substance can be challenging so some people cover the balls with a small plastic bag or plastic cling wrap before applying the Tangle-Trap. There are "recipes" for mixtures of sugar, vinegar and water that can be placed in containers in the trees to attract the apple maggot flies. Although these mixtures do attract and kill some of the apple maggot flies, they also attract many beneficial insects and are, therefore, of questionable value. Sanitation is very important in reducing apple maggot numbers. When infested apples fall to the ground, the maggots exit the fruit and burrow several inches into the soil to pupate. Therefore, it is important to dispose of apples as soon as they have fallen to the ground to reduce the number of overwintering pupae in your orchard. Feed the apples to livestock or bury them at least one foot deep. Do not place them in your compost bin.