2007 Annual Report

Many Pacific spider mite six-legged larvae from a commercial insectary. Photo by Jack Kelly Clark.

Refining IPM for spider mites

Growers in the San Joaquin Valley are all too familiar with how the Pacific spider mite can wreak havoc on their tree crops. To effectively manage the mite, they need to use a full arsenal of cultural, biological, and chemical controls. Recently, however, eight new miticides were registered for use, giving scientists a chance to reevaluate the way all of these control options are integrated into a season-long IPM program.

UC IPM and Entomology Advisor David Haviland has spent the last three years developing information on spider mite IPM. His initial efforts helped define the pros and cons of new miticides and to functionally categorize them. For example, miticides containing etoxazole, spirodiclofen, hexythiazox, and clofentazine are all mite growth regulators that work relatively slowly, but provide long residual effects on mites when populations are low early in the season. On the other hand, miticides containing bifenazate, fenpyroximate, and acequinocyl all work by direct contact on mites and provide excellent knock-down capabilities late in the season.

Haviland is now expanding on this initial work to develop season-long approaches to mite management that incorporate the best use timings of each miticide with information on biological control and treatment thresholds. These approaches are being evaluated in large-scale trials that have incorporated more than 250 acres of almonds over the past two years. 

Results from these trials have helped answer key questions such as whether preventive abamectin treatments are still needed in almonds, and whether new reduced-risk alternatives to propargite can be used effectively.

This work has also led to the potential for increased resistance management and conservation biological control. "Multiple control options are available for any time of the season that allow biocontrol organisms to continue to function, as well as products that can be rotated for the purposes of resistance management," says Haviland. 

Haviland has distributed annual worksheets on the principal miticides that are registered in California, the crops on which they are registered, and their target sites and modes of action.

Over the next several years, Haviland will continue spider mite research to further define optimal IPM approaches for permanent crops in California.

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