Inside this issue:
Alway's Areawide IPM page
Areawide IPM page (with CAMP site descriptions)
...WSU-TFREC Entomology home
...Index to Areawide IPM Update newsletters
Cooperating agencies: Washington State University, Oregon
State University, University of California, U.S. Department of Agriculture,
and Chelan County.
Cooperative Extension programs and employment are available to all without
Kaolin particles: a new product for orchard pest control
Kaolin particles are a natural product derived from kaolin clay that is being investigated as a pest control material. Research with "kaolin particle films" has shown some promising and often surprising results for the control of both tree fruit diseases and arthropod pests. Tom Unruh, entomologist with the USDA-ARS lab in the Yakima Valley, has even been heard to say that this product, with regard to certain tree fruit pests, can "kick caudal segment!"
Research with this product began in 1992 by Mike Glenn, Gary Puterka and colleagues at the USDA-ARS lab in Kearneysville, West Virginia. Based on the idea that plant diseases need wet leaves for infection to occur, they sought to waterproof the plant by coating it with a dust of clay particles treated to make them water-repellent, or hydrophobic. Disease damage was reduced significantly by this treatment and, surprisingly, so was damage by several insect pests. Glenn and Puterka developed in 1996 a kaolin formulation that could be suspended in water, allowing applications with conventional spray equipment. In 1997, research was expanded to other sites, including studies conducted on apples and pears by Tom Unruh and Alan Knight of the USDA-ARS lab in the Yakima Valley. Their research used both treated (hydrophobic) and untreated (hydrophilic) kaolin particle formulations; apparently, the hydrophobic treatment is not needed for insect control. They applied the kaolin using both hand guns and speed sprayers, generally at a rate of 25 pounds/100 gallons with the trees sprayed to drip.
In their work they found dramatic effects on several arthropod pests. The kaolin particles apparently kill nothing. Rather, they act as a repellent barrier, one that encourages insects to leave or not settle down, and to deposit few or no eggs on the treated surfaces. Pear psylla adults avoided trees treated with kaolin and laid few eggs on them. There was a 5 to 10-fold reduction in psylla egg numbers compared with an untreated control, following several early season kaolin applications, and they observed an over 95% reduction in psylla nymphs one month after the applications began. White apple leafhoppers, both nymphs and adults, "bailed out" following kaolin applications, leaving the treated trees for parts unknown. Thrips, apple rust mite and predatory mites were lower in kaolin treated plots. This effect on mites may be a concern with integrated mite management on apples, but could fit better with the management of rust and spider mites on pears. Some suppression of green apple aphid was seen. However, use of kaolin in one study apparently reduced parasitism of leafminers, resulting in higher leafminer populations in the treated trees.
Codling moth control results with kaolin were less dramatic. Repeated applications reduced codling moth damage from 30 to 90% in several trials when compared with the untreated controls, but was still not commercially acceptable. Moths laid few eggs on treated surfaces, when given a choice. Leafroller moths also avoided depositing eggs on kaolin-treated leaves, and delayed dormant applications reduced significantly the number of emerging overwintered larvae that established feeding sites.