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Control programs established for exotic pistachio pest

The Issue

For several decades, California pistachios suffered few pest problems. However, this changed in the late 1990s when a new species of mealybug was found in a Tulare County orchard. By 2002, Gill’s mealybug had infested about 20 acres of pistachios in Tulare County; by 2007 it had been found in more than 5,000 acres of pistachios statewide.

Gill’s mealybugs damage pistachios by feeding on carbohydrates that would otherwise be used for nut development. This results in fewer of the highly prized split, in-shell nuts in exchange for smaller kernels in closed shells. Growers with infested fields applied multiple pesticide applications on a yearly basis to try to prevent significant crop losses. In 2004, the California Pistachio Commission approached the University of California for assistance in finding a solution.

What Has ANR Done?

A team of UC researchers, led by entomologist David Haviland and pistachio expert Robert Beede, worked closely with members of the pistachio industry to develop a management program for this pest. Research was conducted on pest biology, the impact of mealybugs on the yield and quality of nuts, and on biological and chemical control strategies.

The results were used to develop an effective and economically acceptable management program for Gill’s mealybug. The program is based on the use of a single application of a highly effective insect growth regulator, buprofezin, at a time of year when the mealybugs are in their most susceptible “crawler” growth stage. If done properly, this management program can provide two years of effective control.

The Payoff

Improved pistachio quality, lower costs and reduced environmental impact

Nearly 100 percent of the pistachio growers across the state who are battling Gill’s mealybug have now used this program with great success. Most have been able to achieve two years of excellent control for less than half the cost previously required annually for moderate control. Additionally, the transition away from broad-spectrum insecticides has had environmental benefits related to the preservation of biological control organisms and increased worker safety.

This project has allowed growers to produce better quality pistachios while cutting costs and, at the same time, promoting human health and safety, and protecting the environment.


Supporting Unit: Kern County

David Haviland, (661) 868-6215, dhaviland@ucdavis.edu