A Mediterranean Menace

September 28, 2007

Med Fly

Last week, the Eatwell Farm stall at the Ferry Plaza Farmers Market was less colorful than on most late summer days. The stand still brimmed with the usual mix of lavender products, greens, eggs and sweet potatoes, but the farm’s many varieties of tomatoes hung unpicked in the fields. Their absence was due not to labor shortages, blight, rot or other common vagaries that affect harvest, but rather government intervention: all of Eatwell’s fruit crops are quarantined by the state of California.

On September 10, one of the world’s most destructive agricultural pests, the Mediterranean fruit fly, was found in Solano County, where Eatwell Farm is based. Hundreds of different crops are fodder for the “Medfly,” and it can survive in a range of climates. Medflies, which are a bit smaller than house flies, infest fruit and feed on the pulp, making it inedible. Though there are no signs of infestation on Eatwell Farm, its proximity to the site of discovery (three miles) situates it within a 114-square mile quarantine zone created to prevent the fly from spreading.    

This outbreak is the latest of many in California in the last 30 years, but just the second in the Central Valley, California’s agricultural heartland. Based on genetic testing of the flies, officials are guessing that Medfly maggots entered the state on a piece of fruit brought back from Hawaii by a vacationer. After a few flies and many maggots were discovered on a peach tree in a Dixon backyard, the California Department of Food and Agriculture (CDFA) initiated with impressive expediency the battery of tactics that has become standard for Medfly infestations.

The control techniques include a quarantine of all fruit within a certain radius, stripping trees within 100 meters of the discovery site, setting traps, and spraying organic pesticides. In addition, more than a million sterile male fruit flies, dyed pink so that they can be easily distinguished, were released aerially into the Dixon area on September 14. Three million additional flies will be released every week for at least the next nine months. The sterile insects breed with the wild females, spoiling their chances for reproduction.

medflyThough these measures may seem an extreme response to just a few flies, the potentially devastating effects of the pest on California agriculture warrant radical action. According to the California Department of Food and Agriculture, “A permanent infestation would result in estimated annual losses of $1.3 to $1.8 billion.”

Nigel Walker, owner and farmer at Eatwell Farm, has been chronicling the effects of the outbreak on the farm’s blog. One of his most adamant messages to customers is not to bring food across state lines. Writes Nigel:

I am exhausted and determined to comply with this quarantine so that the Medflies are stopped in the City of Dixon. The message we all need to hear is that our food security is at stake here. Do not bring any food into California.…The rules at our borders are there for a very good reason. Please for the sake of your food supply, all our farms and livelihoods abide by these rules.

Just one piece of fruit can harbor enough Medfly larvae to cause tremendous problems for California farmers. The growth of global commerce and tourism presents innumerable opportunities for pests to travel. Enforcement of quarantines is difficult, and travelers have a responsibility to resist bringing fruit across state and country borders. The survival of local farms may be at stake.

The quarantine will last at least through July of 2008, but farmers in the quarantined area will be able to ship fruit outside the zone if they comply with strict precautionary measures. Within a month, Eatwell Farm should be able to begin bringing some fruit to market, but by that time, the season for tomatoes and other quarantined summer crops will be nearly over.

Learn more:

Eatwell Farm blog >

San Francisco Chronicle article >

CDFA website >