Protecting Fruit Trees from Apple Maggots

Apple maggots, also known as railroad worm, can be a frustrating problem for homeowners with apple trees. Often, it’s easier for commercial growers to protect hundreds of trees than it is for homeowners to protect one or two trees in the landscape. If a neighbor’s apple tree is uncared for, a homeowner’s effort to eradicate the pest may be in vain. However, there are things homeowners can do to ensure they get a decent crop of fruit.

Life Cycle of the Apple Maggot

Apple maggots over-winter in the ground around apple and fruit trees. They emerge as small flies anywhere from late June through September with a peak in late July through early August. After feeding for 7-10 days, female adult flies pierce the skin of the apple and deposit eggs in the flesh of the fruit.

These eggs hatch approximately 5-10 days later as a maggot. The maggots then feed on the flesh of the apple for the next 3-4 weeks. They finish their development when the apple falls to the ground. The maggots exit the apple and burrow into the ground where they will lay until the following spring when they emerge again as flies.

Apple maggots damage fruit in two ways. First, at the point where the female flies pierce the fruit and deposit eggs, the apple stops growing. This gives the apple a dimpled and misshapen appearance. These areas may be discolored or covered with a waxy coat. Second, once the eggs hatch, the maggots will tunnel through the flesh of the apple. These trails are brown and eventually cause the apple to rot.

Non-Pesticide Control of Apple Maggots

The most important step in controlling apple maggots is good sanitation. Once apples fall from the tree, the maggots will exit the apples in a few days to burrow into the ground. Pick up apples and destroy them to prevent the maggots from over-wintering in the soil.

Adult flies can be prevented from laying eggs with sticky traps. Traps consist of red balls covered with a sticky attractant. These traps are hung in the apple tree at a rate of one trap per 100 apples. Flies are lured to the trap and become stuck and eventually die without laying eggs. Traps are available from garden retailers or mail order sources.

Another way to prevent flies from laying eggs is to cover the apples with plastic bags. Make sure the apples are covered before the flies start to emerge. Tie the bag loosely around the stem of the apple and cut a small hole in the corner of the bag to allow for drainage. This method is good for younger trees which are not producing a large number of apples.

Chemical Control of Apple Maggots

Spraying for apple maggots is highly dependent on timing. Application of pesticides must occur after the flies emerge from the ground and before they lay eggs. Once the flies lay eggs in the apples, pesticides are of no use.

There is a about a 7-10 day lag between the emergence of the flies and their egg laying. Pesticides must be applied during this time and cover all leaves and fruit on the tree. Recommended pesticides include carbaryl or phosmet. Traps can be used in conjunction with pesticides to determine when flies are emerging. Otherwise, an application can be done every 7-10 days starting July 1. Follow directions on chemical packaging for when to stop spraying for harvest.

Apple maggots can be frustrating for home gardeners who are expecting an apple crop. Using good sanitation practices is the first step to disrupting the life cycle of this destructive pest. Timing pesticide spray is crucial to prevent the adults from laying eggs. With a little persistence, home gardeners can control apple maggots and harvest a good fruit crop.

Sources:

Hahn, J. and M. Ascerno. Apple Maggot Management in Home Gardens. WW-01007, University of Minnesota Extension, 2005. http://www.extension.umn.edu/distribution/horticulture/DG1007.html

Miller, R.L., J.A. Steele and A.W. Smith. Apple Maggot and Its Control. FactSheet HYG-2041-88, Ohio State University Extension. http://ohioline.osu.edu/hyg-fact/2000/2041.html