Addressing Gill’s Mealybug Populations in Pistachios

Brian German Industry, Nuts & Grapes

Although a relatively new pest for pistachio growers, Gill’s mealybug has been shown to be a significant concern for the industry. The pest has proved to be problematic due to the overlapping of generations. Early season monitoring is going to play a critical role in any plans for mealybug control.  

Gill's Mealybug

“Gill’s mealybug normally has three generations per season, it’s kind of this May-June, July-August and then the third generation is in September,” said Rick Leonard, Customer Business Advisor with Bayer Crop Science. “We start monitoring probably the very first part of May, end of April, start really watching for how it’s emerging.”

A three-year study cited in the University of California Integrated Pest Management Guidelines showed that a treatment in the beginning of June would be economically justified if one insect was found per every 10 clusters during May monitoring. Leonard recommends using Admire for early season control and Movento as a foliar application in early Summer.

“We usually try to target mid-May. The most important thing is that we really want to get the Movento into the tree for controlling that first crawler stage that comes out towards the end of May-first part of June,” Leonard explained. “Make sure that you’re ahead of the crawler emergence two to three weeks because it’s going to take two to three weeks for that material to get in the tree and to be able to control the young crawlers.”

Mealybug populations create significant concern for growers as the pest feeds within the pistachio cluster, taking important nutrients away from nuts during the development stage. Mealybug feeding can also produce a significant amount of honeydew, leading to black sooty mold issues.

“Growers are very well aware of the sticky clusters that it causes which leads to staining which gets a deduct at the processor.  It reduces nuts size and the grower gets discounted at the processor,” Leonard noted. “Gill’s mealybug can result in significant costs both in yields and quality of their crop.”

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Brian German

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Ag News Director, AgNet West