Updated 03/04/09

Apple Maggot - Unwanted in Washington

For more information, e-mail us or call (509) 249-6966.

Apple Maggot Facts

Why the apple maggot is a significant threat to fruit crops

• Directly attacks fruit, making it brown, mushy, and inedible.
• Key fruit attacked are apples, crabapples, cherry, pears, plums, and apricots.
• If left unchecked, would have devastating impact on the apple industry, the number one cash crop in Washington.

History of the apple maggot in Washington

• First detected in 1980 in Clark County.
• Soon spread up the Interstate 5 corridor.
• Now present in 22 of Washington's 39 counties.  This includes:  17 western Washington counties (Clallam, Clark, Cowlitz, Grays Harbor, Island, Jefferson, King, Kitsap, Lewis, Mason, Pacific, Pierce, Skagit, Snohomish, Thurston, Wahkiakum, and Whatcom), two counties in the Columbia Gorge (Skamania and Klickitat) and one county in eastern Washington (Spokane). Yakima and Kittitas are partially infested counties in eastern Washington.

How the apple maggot is spread

• Mostly by people transporting apples from infested backyard apple trees to non-infested areas of the state.
• Some spread due to abandoned orchards.
• Some spread also due to natural spread -- a very slow process.

WSDA's apple maggot control program

• Established in 1980.
• Administered in concert with the Apple Maggot Working Group, made up of representatives from Washington State Dept. of Agriculture (WSDA), Washington apple industry, tree fruit research community, and the federal government.
• Consists of three components: A survey and regulatory component administered by WSDA; a control, suppression and eradication component administered by county pest boards; and an education component conducted by Washington State University through its cooperative extension offices.
• Apple maggot trapping program conducted annually. Between 5,000 and 8,500 apple maggot traps placed in field each summer. Field activities determined by WSDA and Apple Maggot Working Group.
• Trapping results forwarded to county pest boards for control, suppression, or eradication actions they consider appropriate.
• Counties may be quarantined in whole or in part based on trap catches and other evidence of apple maggot activity detected.

Purpose of apple maggot quarantine

• Facilitate the movement of commercial fruit to domestic and international markets by providing shippers with one of two types of WSDA documents certifying their fruit is apple-maggot free.
• One certificate states no apple maggot flies were caught within a half-mile of the orchard shipping the fruit. The other certificate states flies were caught within a half-mile of the orchard, but WSDA inspection revealed no apple maggot larvae in the fruit.

Success of apple maggot control program

• Apple maggots have never been found in commercially packed fruit in the state.

Additional sources of data

• Apple maggot control program: Dr. Brad White, WSDA pest program manager, telephone (360) 902-2071. 
• Apple Maggot Working Group: Dr. Mike Willett, current chairman, telephone (509) 453-3193. Dr. Willett is Vice-President for Scientific Affairs, Northwest Horticultural Council.
• Garden Friends and Foes - Apple Maggot: WSU Extension Office, Whatcom County. 
• Protecting Backyard Apple Trees from Apple Maggot: WSU Extension Office, Yakima County.