Problem type: Insect
Name of problem: Apple Maggot
Plant name(s): Crabapple, pear, plum, apple, hawthorn, apricot
Symptoms / Characteristics:
Small, minute, brownish punctures are evident in the skin of the fruit. Females lay eggs, creating small pitted or dimpled areas on the surface of the fruit. Tunnels from larval feeding will be evident inside fruit. Fruit appears discolored and browning, with the characteristic dark track marks associated with tunneling best seen when the fruit is cut open.
Once larvae are mature, they leave the fruit, dropping to the ground to pupate. Apple maggots overwinter as pupae in the soil under the host tree. Adults emerge from late June-September and resemble other fruit flies. The adults are half the size of house flies, measuring about 5-6 mm, black in color and have a prominent white spot on their backs. Adults have a distinctive wing pattern of clear wings with 4 black bands. Shortly after the adults emerge, eggs are laid under the skin of the fruit using small puncture holes. Adults do not damage the fruit but lay their eggs in it. Eggs then hatch and the white legless larvae feed on the fleshy fruit until they are mature 20 - 30 days later. Apples drop and the larvae pupate and overwinter in the soil as pupae. There is one generation per year.
The apple maggot is not picky regarding climate and can adapt to various weather conditions. They can withstand more cold temperatures than many other insects.
Control / Preventions:
Once fruit is infested with maggots, days of feeding will cause fruit to eventually drop to the ground. Collecting fallen apples shortly after the fruits have fallen can prevent maggots from leaving the fruit and burrowing in the soil to overwinter. Place infested apples in tightly sealed plastic bags and dispose.
Control is done during the adult stage. Yellow sticky traps can detect adult flies. Red spheres coated in Tanglefoot® or another adhesive, can also be hung in trees by the end of June to trap adult flies wanting to lay eggs. The red spheres resemble apples, and were developed specifically for the apple maggot. Traps are useful to time spray applications for adult control. Spray with Sevin at the end of flowering. Avoid spraying any earlier as this will kill the pollinating bees. Ensure thorough coverage of all foliage. Three more applications should be made at 10-day intervals. By this time, there should be no adults around. Some flies do not emerge until the 2nd, 3rd or 4th year, so complete eradication in one year is not possible.
Keep the ground free of leaf litter and debris. Do not use infested fruit in a compost pile as this only enhances the development of the larvae. Another simple solution is to avoid planting or remove susceptible host plants.