Apple Maggot in Utah

Apple Maggot in Utah

apple maggot adult on plum

Apple maggot is a true fruit fly in the Family Tephritidae. It has a prominent ‘F’ banding pattern on its wings, and the larvae tunnel into pome, stone, and some ornamental fruits. Female flies have a sharp ovipositor for laying eggs under the skin of ripening fruits.

Apple maggot primarily infests native hawthorn in Utah (Crataegus rivularis), but recently it has been found in home garden plums (Prunus domestica) in the Salt Lake Valley. It is a quarantine pest in Utah, regulated by the Utah Department of Agriculture and Food. Its presence in commercial fruit production areas can inflict substantial economic harm through loss of export markets. In addition, infestations cause fruit damage which could increase insecticide use in orchards, disrupting integrated pest management programs.

wing pattern of apple maggot

Apple maggot is native to northeastern and north central North America, where it historically fed on fruit of wild hawthorn. In the eastern U.S., it is primarily a pest of apple, and requires a consistent insecticide program to keep fruit maggot-free. Apple maggot was first recognized in Utah in 1983, but an extensive survey of the state in 1985 showed that it was widely distributed in northern and west central regions of the state where it was most likely feeding on fruits of river hawthorn and unmanaged cherry. These facts implicate that apple maggot is likely native to parts of Utah.

apple maggot larva in plum
Apple maggots are typically known for infesting apples, but in Utah, recent infestations have been in plums.

In the mid-1980s, there was a small flush of findings of apple maggot flies on traps in non- and low-managed cherry orchards in northern Utah. Removal of abandoned orchards and elevated attention to management in nearby commercial orchards reduced its presence, and concern for its management diminished over time. To date, apple maggot has not been identified from apple fruits in Utah.

In 2013, the Utah Plant Pest Diagnostic Lab diagnosed apple maggot in plum fruits from several home gardens in Salt Lake County. In addition, several suspect apple fruit samples were submitted with possible insect tunnels, but no larvae were found. An effort is underway to educate home gardeners and producers about this fruit fly pest, and its potential to cause crop loss and economic harm to the state’s fruit industry.

The risk for infestation by apple maggot is increased when fruittrees are left unsprayed and when they are growing near stands of native hawthorn. The key management strategies for apple maggot include mass-trapping (place multiple traps in fruit trees), sanitation (remove hawthorn trees and destroy infested fruit), ground barriers (place impenetrable mulches underneath infested trees to reduce access of larvae to soil), and insecticides (those used for cherry fruit fly will work on apple maggot).

Best management practices for commercial orchards at risk for apple maggot infestation include prompt and thorough removal of fruit at harvest, removal of nearby hawthorn stands and unmanaged fruit trees, and maintenance of an effective insecticide program when susceptible fruit is present.

  

pherocon trap red ball trap
Apple maggot can be monitored with either yellow sticky traps or red sticky spheres. Adding ammonium carbonate or acetate as an external bait is critical to improve effectiveness of the trap.

 

USU Extension has produced an apple maggot fact sheet with more information, and will trap for this pest in hot spot locations. There are several types of effective traps for monitoring apple maggot in fruit trees: rectangular yellow sticky traps and plastic red balls. It is critical to add an external bait of ammonium carbonate or acetate to either style of trap to enhance its attractiveness to fruit flies.

Fruit becomes susceptible to egg-laying by fruit flies once the skin begins to soften and color. A degree-day model (based on temperature) is available to predict its development. Apple maggot management and timing information will be provided in the Tree Fruit Integrated Pest Management Advisory. You can sign up for a free subscription to the tree fruit and other IPM advisories here. Advisories are delivered by e-mail throughout the growing season to inform gardeners and growers about current insect and disease activity, and provide practical management recommendations.

- Diane Alston, Entomologist