An adult Rhagoletis pomonella fly (photo from Penn State)

A destructive pest in commercial and backyard orchards alike, the apple maggot or Rhagoletis pomonella is native to the northeastern United States and is also known as the “railroad worm” due to the speed at which the maggots dig through the apple and the tunnels they create! While the larva resemble white, 1/4-inch maggots, adult flies have yellow legs and transparent wings with characteristic W-shaped dark bands. ​Contaminated fruits often ​show​ small dimples or pitted areas ​on the apple surface ​​with brown or rotten trails running throughout the flesh along with an associated bacteria.

Initial damage from apple maggots appear as small dimples on the fruit surface, but they can quickly destroy fruit from the inside (photo from University of New Hampshire)

Infested apples drop prematurely and the mature maggots leave to pupate in the soil. In Pennsylvania, there is only one generation per year; the pupae overwinter in the ground until the following June, with peak emergence of new adult flies around July and August. Early maturing and thin-skinned apples are often most severely infested because it’s easier for the maggots to pierce the skin of the fruit to lay their eggs. Apple maggots will also attack plum, apricot, pear, cherry and hawthorn. If trees are neglected, 100% of the crop can be wormy rendering the fruit unfit for human consumption.

An apple maggot peeking out of the tunnel it bored into this apple (photo from Missouri Botanical Garden)

Apple Maggot Management

Luckily, there are a few ways to organically manage apple maggots in your orchard. The first is to collect and destroy dropped fruit daily until fall in order to prevent more maggots from breeding. In addition, adult flies may be trapped before they can lay eggs in new crops. Sticky red sphere traps such as these can be hung within bright spots in the canopy from early summer until harvest. It’s recommended to set out one trap for every 100-150 apples: six per full-size tree and one or two for dwarf trees.

Commercially available apple maggot traps are fairly effective in reducing populations (photo from Missouri Botanical Garden)

Young fruits can be covered with plastic baggies or nylon footies to physically prevent insect pests from entering the fruit. They can even be made into an art installation such as this project in Seattle named “Blushing Orchards,” in which volunteers covered young apples with variously dyed “footies” that applied color theory to evoke a particular mood from each visitor to that orchard. Another strategy is to plant clover as a ground cover to attract beetles that will prey on the pupae in fallen fruits and the soil. If starting a new orchard, consider growing late-maturing cultivars as a prevention strategy. However, these methods will not be effective if infested, abandoned apple trees are nearby — ideally, abandoned apple trees and alternate hosts within 100 yards of the orchard should be removed.

These nylon barriers expand as the apples grow and their installation could be a fun art project that engages the community around your orchard (photo from Seattle Office of Arts and Culture)

Additional resources

This edition of POP TIPS prepared by 2019 POP Intern Piotr Wojcik. 

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