Gilli mealybug is a new pest of deciduous trees in California. It is primarily a pest of pistachios, but has also been found in almonds and grapes. It is important to quickly identify and treat new infestations of this pest in an effort to minimize its spread.
Gilli mealybug can reach 1/2 cm in length and has a pink body covered in white filamentous waxy excretions. When looking from the top, it appears to have two pink stripes running down the length of its body and two white tails. Gilli mealybug feed by sucking plant juices and produce large amounts of a sticky liquid called honeydew. This liquid supports the growth of sooty mold which can turn bark, leaves, and nuts completely black.
During the fall, Gilli mealybug aggregate on the trunk and main scaffolds and produce offspring that overwinter in the cracks of the bark. This is an easy time of year to find the mealybugs due to the furry appearance given to the bark.
During the spring, Gilli mealybug feed on the stems, leaves and then fruit. In pistachios they prefer to feed within the cluster just prior to harvest when they can reduce nut quality and possibly yields.
Growers of any nut, stone, or pome fruits who find mealybug infestations are encouraged to report them to their local UC Cooperative Extension office.