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Medflies: It Just Takes Two

Where were we? Right, Medflies. You’ve been seeing the signs of a quarantine (such as netting over produce) in farmers’ markets in Santa Monica, Culver City and adjoining areas (see my original post on the subject here).

They’re not beneficial insects — they don’t pollinate fruit, they destroy it — so once their presence has been detected, they must be dealt with to prevent further infestation. I spoke with sources at both the USDA (U.S. Dept.of Agriculture) and CDFA (California Department of Food and Agriculture), the agency responsible for inspection and eradication. The CDFA does not use blanket pesticides to treat Medfly. For the past 15 years, the go-to method has been the release of sterile flies (SIT) that breed with wild flies — in effect, to create an orgy into oblivion (here’s a fact sheet).

According to Steve Lyle, CDFA Director of Public Affairs, “This has been very successful as a biological alternative to large-scale pesticide use. We’re always looking for that nexus of environmental sensitivity and efficacy, and [SIT] is far more effective, cost efficient, and environmentally sound. It works as an exclusion tool, not just for eradication, and has greatly reduced the number of infestations since the program’s implementation. The project is called the Preventative Release Program.”

Here’s how it works. Sterile fruit flies are air dropped on a daily basis over the L.A. basin (L.A., Orange, Riverside, and San Bernardino counties). County ag inspectors all over the state regularly patrol their beats, looking for evidence of Medfly (mostly through a trapping program), as well as other crop-damaging pests, such as Light Brown Apple Moth or Asian Citrus Psyllid.

If there is an infestation — and this can designated because of as few as two flies, the number found in Santa Monica last October — four things happen to prevent, exclude, and eradicate. The number of sterile flies to be airdropped in the affected area is quadrupled; a quarantine is put into effect; infected fruit is stripped away; and Spinosad, a certified organic insecticide derived from soil microbes, is topically applied to the foliage of host material trees within a 200-meter radius of the fruit fly find site. The application acts as bait for emerging Medflies who need to eat before going on their sex spree.

I know: That the insecticide is certified organic is cold comfort to some, and I refer you to Cornell University’s resource guide for more information. I can tell you that the sustainable-practices farmers I spoke with are glad such tools exist.

So, if only two fertile flies were found, why the long quarantine? Since a biological approach depends on stopping propagation, an area remains quarantined through three Medfly life cycles, usually seven to ten months. If no new evidence is found, eradication is considered complete and the quarantine is lifted.

I asked the farmers how they dealt with the situation. The consensus: It’s a fact of farming, especially in today’s global life. If anything, the L.A. quarantine raises awareness among customers about what farmers have to contend with to keep California crops safe.

If you have additional questions for CDFA, you can email: officeofpublicaffairs@cdfa.ca.gov

Amelia Saltsman is the author of the Santa Monica Farmers’ Market Cookbook.


1 Response for “Medflies: It Just Takes Two”

  1. Erik Knutzen says:

    An alternate take on this issue is that the Medfly has been here for a long time and that it can’t be eliminated. UC Davis entomology professor James Carey characterizes CDFA’s medfly program as, “throwing money down a rathole.” See http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=2154 for more on his views. The CDFA was almost eliminated last year–they have a strong incentive to justify their existence.

    As to CDFA spokesman Lyle’s claim of “environmentally sound” practices I would suggest asking him why they are using a neonicotinoid pesticide, banned in many European countries for harming pollinating insects, in their ongoing Asian Citrus Psyllid program.


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