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NMSU Extension expert says apple maggots a threat to Valencia County apple growers

LOS LUNAS, NM - This year's warm spring has brought an unwelcome surprise to Valencia County's apple growers - the early emergence of apple maggot flies.

An apple with larva in it.
Damage caused by the developing apple maggot may not be visible until the apple is cut open at harvest. (NMSU photo by Tess Grasswitz)
The apple maggot
Adult apple maggot flies are slightly smaller than house flies, with a distinctive F-shaped pattern on their wings. (NMSU photo by Tess Grasswitz)
A bud with a material wrapped around it.
Commercially available "Maggot Barriers" can keep apple maggots out of back-yard fruit if applied early enough. (NMSU photo by Tess Grasswitz)

New Mexico State University Extension agricultural agent Kyle Tator says this could be economically damaging to all apple growers, whether they have a single tree in their back yard or a commercial orchard.

"It has been verified that there are apple maggots in Valencia County," Tator said. "This is a major problem we must take seriously."

This pest is native to the eastern United States. Although it has been present in Northern New Mexico since 2003, it first reached Valencia County in the summer of 2010.

"However, it may have been temporarily forgotten by local growers, since last year many lost their apple crop to a late frost." said Tess Grasswitz, Extension integrated pest management specialist at NMSU's Agricultural Science Center at Los Lunas.

Growers are accustomed to dealing with Codling moth, the main pest of apples in this area, but apple maggot is more difficult to control because the female fly lays her eggs beneath the skin of developing fruit instead of on the surface, which puts them out of reach of insecticides.

"The developing larvae - small, cream-colored 'maggots' without an obvious head or legs - feed inside the fruit and their damage may not be visible until the apple is cut open at harvest," Grasswitz said. "Infested fruit may drop prematurely from the tree and the larvae complete their development in the soil, where they can remain for one to two years."

Commercial growers must use carefully timed sprays to target the adult flies before they start laying eggs, but the problem can persist if owners of back-yard trees fail to do likewise.

"Homeowners who do not wish to spray their trees can help by either bagging the small developing fruits with mesh "Maggot Barriers," or collecting and destroying windfall apples as quickly as possible," Grasswitz said. "It is also important not to transport infested fruit to other parts of the state that don't currently have the pest."

Further information on control of apple maggot is available from Kyle Tator, Valencia County Extension agent, at 505-565-3002.