Hero Image

New invasions of eye gnats in Southern California

The Issue

The community of Jacumba in San Diego County was afflicted with an enormous population of eye gnats -- small flies that hover around eyes, ears and nose. In large numbers, eye gnats can be exceptionally bothersome. Outdoor activity in the mornings and evenings became impossible. Eye gnats are a native inhabitant of the desert southwest and San Joaquin Valley of California, but with the introduction of modern farming practices and irrigation, eye gnat populations have exploded in some areas near farm fields. Control methods have been ongoing since the early 1950s, most notably in Riverside County's Coachella Valley.

In 2008, the residents of Jacumba blamed the local 400-acre organic farm for a high population of the troublesome gnats and complained to county officials. There was no avenue for action by the county, and the interaction among the county, the farmer and the community turned acrimonious. This serious urban/agriculture interface issue threatened organic food production in the area and the residents' quality of life.

What Has ANR Done?

The County Department of Vector Control asked UC Cooperative Extension in San Diego County to investigate the issue. Advisors conducted research to determine the source of the eye gnats and confirmed that it was the organic farm. Working with the farm owner, UCCE advisors developed management practices to reduce eye gnat propagation on the farm. These practices were modified until the eye gnat population was significantly reduced in the community.

The Payoff

UC advice results in 99.9 percent reduction in eye gnats

UC Cooperative Extension research helped to solve an urban/agriculture interface problem thought to be insurmountable. It also provided the farmer with methods that will allow him to farm organically in close proximity to an urban center. San Diego County Vector Control used the recommended practices to create an Eye Gnat Nuisance Prevention Plan. Implementation of the management plan resulted in a 99.9 percent reduction in eye gnat numbers in town. Similar eye gnat problems are occurring in several other San Diego County communities. UCCE is now involved in problem solving in those areas as well.


Supporting Unit:

James A. Bethke, Floriculture and Nursery Farm Advisor, UC Cooperative Extension, San Diego County and Bryan Vander Mey, SRA, UC Cooperative Extension, San Diego County
James Bethke, (760) 752-4715, jabethke@ucdavis.edu