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November 30, 2005

IPM programs being developed for new mealybug plaguing pistachio growers

A two-tailed pest is hitchhiking its way across California at breakneck speed, feeding on pistachios, almonds, and grapes, and surviving in a wide range of climates. Researchers, though, believe that integrated pest management programs developed this year will help control the pest where it is located and help slow its spread.

The new gilli mealybug, Ferrisia gilli, was first identified in pistachios near Tulare, California, in 1998. Since that time, it has spread to more than 3,000 acres of pistachios statewide.

   Ferrisia gilli is a new pest of deciduous trees in California.

Ferrisia gilli is a new pest of deciduous trees in California.
Photo by David Haviland

Management programs for the mealybug in pistachios during the last few years have revolved around the use of two organophosphate and carbamate insecticides. “Multiple applications of these products provide some control, but are in no way a substitute for an integrated pest management approach,” says David Haviland, entomology farm advisor for Kern County and UC IPM advisor. “Transitions to an IPM approach became more of a reality in 2005 because we gained a better understanding of the mealybug’s biology and how it interacts with its host crop. This has allowed us to identify some weak links in its life cycle that can be exploited. The registration of a very effective insect growth regulator, buprofezin, has also aided in the process.”

The potential for biological control of F. gilli is huge, says Haviland. With funding from the California Pistachio Commission and Almond Board of California, he found that heavy mealybug populations in almonds could be reduced naturally to near undetectable levels without the use of chemical insecticides. Mealybug reductions were attributable to at least two species of parasitic wasps, a predatory beetle, lacewings, and possibly ants. Haviland is collaborating with UC Berkeley biocontrol specialist Kent Daane to investigate the role of these different biological control organisms to see how each can be used to control F. gilli in different cropping systems.

F. gilli belongs to a type of mealybug that is found throughout the world, feeding on many different plants. The pest is believed to have originated in the southeastern United States. In California, in addition to pistachios, it has been found in almonds, grapes, persimmons, stone fruits, and several ornamentals such as fruitless mulberry.

The insect has a pink body covered in white filamentous, waxy excretions. It has two pink stripes running down the length of its body and two white tails. The mealybugs feed by sucking plant juices, and they produce large amounts of a sticky liquid called honeydew. This liquid develops into a sooty mold that can turn bark, leaves, and nuts completely black.

During the fall, adult female mealybugs congregate on the main scaffolds and trunks of trees and vines, giving it a white, bearded appearance as if draped in cotton candy. This is an easy time of year to find the mealybugs due to the furry appearance they give to the bark. The females produce large numbers of offspring that stick around during the winter in cracks and crevices.

During the spring, the pest feeds primarily on woody parts of the plant. As the season progresses, they move onto fruiting structures and hulls in pistachios, where they can reduce nut quality and possibly yields.

“Due to the widespread range of this pest, it’s difficult to predict where it’ll go next,” says Haviland. “Even growers who don’t yet have this pest should focus on preventing its spread. They can accomplish this by keeping work crews and equipment that have been in infested blocks out of those that are clean. Equipment such as harvesters, bins, mowers, and disks should be cleaned before moving them from orchard to orchard.” 

Haviland and other UC researchers presented the latest information on the mealybug for pistachio growers, PCAs, and harvesters at a series of meetings in Tulare County in June and August 2005. “In less than a year, we’ve delivered an entire IPM package to growers and pest control advisers with information on how to find the pest, monitor it, its effects on nut quality, and basic biological and control information,” he says. “The cross-commodity nature of this pest will allow us to coordinate efforts of the pistachio industry with those of the almond, grape, stone fruit, and other industries that want to know more about managing this insect.”  

Growers who find mealybug infestations are encouraged to report them to their local University of California Cooperative Extension office.


High-resolution image (852KB) "Ferrisia gilli is a new pest of deciduous trees in California." Photo credit: Courtesy of UC Statewide IPM Program, David Haviland. Photos are for use with this release only. All other uses see Legal Notices.


Stephanie Klunk, Communications Specialist
UC Statewide IPM Program
(530) 754-6724

David Haviland, Entomologist and Pest Management Farm Advisor
UC Statewide IPM Program
Kern County
(661) 868-6215 

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