It’s a billion-dollar business: Washington produces more than 60 percent of the nation’s apple crop. So a pest called the apple maggot is taken very seriously. The maggots were first found in the state in 1980, and officials have tried to limit their spread through a quarantine that prohibits transportation of home-grown fruit from county to county. There’s also a trapping and certification program.

Apple maggots in Washington are controlled in three main ways:

• Through a quarantine area, out of which homegrown fruit may not be transported.

• Through trapping of apple maggot flies, which determines where the maggots may be present and helps orchard owners certify that their crop is maggot-free.

• And local programs that may include education or eradication through spraying.

The costs

Here is how much has been spent in recent years on a trapping and certification program to control apple maggots. The program is run by the state but financed entirely by commercial grower fees.

2011-12 (budgeted): $505,334

2010-11: $492,350

2009-10: $545,912

2008-09: $484,738

2007-08: $499,283

The state also provides funds to county pest-control boards for local eradication and pays for educational materials through Washington State University cooperative extension offices:

2011-12 (budgeted): $10,000

2010-11: $9,953

2009-10: $74,644

2008-09: $83,118

2007-08: $48,591

Apple maggot Q&A

Q: What are apple maggots? A: Apple maggots are larvae of the apple maggot fly, which is native to the northeastern U.S. and eastern Canada. They were found first in Oregon in 1979 and spread north the next year. They are now in 22 of Washington’s 39 counties, including Snohomish and Island, primarily in fruit trees.

Q: Why must they be controlled? A: Apple maggots render their host fruit inedible, leaving it mushy and brown. Female flies deposit eggs just below the skin of an apple or other fruit, such as a crabapple, pear, cherry, plum or apricot, and the larvae feed on the fruit.

Q: What do the highway quarantine signs mean? A: The highway signs in western Washington that say “Apple Maggot Quarantine Area/Please do not transport home-grown tree fruit” let people know that backyard or noncommercial tree fruit grown should not be taken out of Western Washington. Most of the quarantine area covers Western Washington because the apple maggot fly thrives in wet areas.

Q: In what other ways are apple maggots controlled? A: East of the mountains, a trapping program paid for by the state is used to help commercial growers certify that their crop is maggot-free. West of the mountains, any orchard owner who wants to transport fruit outside the quarantine area must have a certificate and pay for the trapping.

Sources: Washington state Department of Agriculture; Washington State University Cooperative Extension