Peach Fruit Fly Update

Peach fruit fly Peach fruit fly found on a sticky trapBetween July 31st and August 14th, 2019, four peach fruit flies were found in the cities of Brentwood and Oakley. The Contra Costa County Department of Agriculture increased fruit fly detection efforts in the area to assess the extent of the infestation. The detection area, known as a delimitation, includes portions of Brentwood, Oakley, and a small part of Antioch. Like other invasive fruit flies, peach fruit flies present a serious threat to the natural environment and our agricultural industry. They feed on a wide range of host commodities, including stone fruit, citrus, tomatoes, pears and figs. When the flies are present, adults will lay eggs under the skin of the fruit. Once the eggs hatch, the larvae, or maggots, tunnel through the flesh, consuming the pulp. This feeding causes extensive damage to the fruit, and the exit holes allow decaying organisms to enter the fruit, which makes it inedible.

Due to the severity of the threat to our natural environment and the agricultural industry, efforts to contain and eradicate the infestation are currently underway. The organic bait Spinosad, in combination with a substance that mimics a female fruit fly pheromone, is being applied in small bait stations on trees and telephone poles in the delimitation areas of Oakley, Brentwood, and Antioch. The male flies, attracted by the pheromone, feed on the Spinosad and are killed. This ultimately breaks the lifecycle of the flies and leads to eradication.

Similar eradication projects occur periodically throughout the state when exotic fruit flies are found. These have all been successful, largely owing to the fact that there is a trapping program in place to monitor for these fruit flies, dedicated staff to manage the eradication efforts, and effective tools that provide low-toxicity treatment options. County staff and officials from the California Department of Food and Agriculture are working together to control the current peach fruit fly infestation and to prevent the affected area from expanding, and eventually eradicate it completely. This important work is done to protect the environment, Contra Costa County’s local agricultural industry, and backyard gardeners, which in turn protects agriculture throughout the state.

The California Department of Food and Agriculture has put out a peach fruit fly Notice of Treatment and map of proposed areas of treatment in Brentwood, Oakley, and Antioch. Additional information on the peach fruit fly may be found on the exotic fruit fly project pages. In addition, Contra Costa County has put out a press release on the fruit fly finds. If you have further questions, you can also call one of our offices in Concord or Knightsen.