Point Reyes Light- November 19, 1998
Apple maggots infest Inverness fruit trees
Apple maggots have spoiled the fruit in the backyards of Inverness and Inverness Park this year, and local gardeners are worried that an invasive fly may be settling for good in West Marin.
The pest rhagoletis pomonella was identified last month by the University of California Cooperative Extension in Santa Rosa, which got samples of worm-ridden apples from the Second Valley orchard of Judith Smith, one of the cooperative extension's master gardeners.
"They've pretty much decimated my apples this year," said Smith, who has watched the maggots spread throughout her 10 apple trees over the last two seasons.
Several other gardeners in the Inverness area say maggots have spoiled their fruit, although the pest has yet to be reported in Marin east of Tomales Bay, said Mario Moratorio, one of the Cooperative Extension's pest advisors.
The apple maggot (its adult form is the apple maggot fly) is native to the northeastern United States and eastern Canada. Over the last two decades it has turned up in apple orchards in Oregon and Washington and to a lesser extent in Northern California. Moratorio speculated that the colony in the Inverness area was caused by travelers carrying infested fruit.
Adult apple maggot flies are about the size of ordinary houseflies, but have a white banding pattern on their wings. The larvae look exactly like other larvae found in apples, except they lack clearly defined head capsules.
Because the worms can only be eradicated by insecticides, they especially difficult to remove from backyards or organic orchards, said Paul Vossen, a UC Cooperative Extension farm advisor.
"If you have apples in your backyards, or for anybody trying to grow apples organically, this is one hell of a pest," he said. "It's a fly, it reproduces rapidly, and it has no natural enemies."
The state Department of Food and Agriculture repealed its quarantine on apple maggot-infested fruit in 1994, and the Marin County Agriculture Commission stopped monitoring for the apple maggot fly soon afterwards, said Andrea DeGrassi, deputy county agricultural commissioner.
Few apple maggot flies were ever found in the county's monitoring traps, DeGrassi said. Neither Marin nor Sonoma County has a local ordinance restricting the movement of infested apples, and the county agriculture commission has no program for eradicating the worm.
Hoping to keep the fly from the commercial orchards about 17 miles to the north around Sebastopol, where it would likely be treated with insecticides, Moratorio said the UC Cooperative Extension will advise West Marin gardeners on how to keep apple maggots under control.
What's most important, he said, is that gardeners keep their fruit to themselves. More information about the worm and its life cycle will soon be made available through the county's cooperative extension office in Novato, he said.
Apple maggots will eat just about every variety of apple, though they seem to appear more often in the types that ripen early, Smith said. The maggots leave meandering brown holes throughout the apple, eventually turning the whole fruit to rotten mush.
Apple maggots can often be distinguished from the codling moth larvae, the more common apple worm, by the absence of caterpillar droppings, or frass, around the apple core, Moratorio said.
Fly traps might keep the numbers down. But unless the apple maggots are completely eliminated, they will likely become a permanent resident in West Marin, he warned.
"We are pretty much in for it," Smith said. "I don't know what our long-range prospects are for containing it. It's only going to spread."