Kaolin Clay for Management of Glassy-winged
Sharpshooter in Grapes

Reduced-Risk Pest Control Factsheet

Abstract

Kaolin particle film barrier as it appears on blueberry. Adequate coverage of all leaf and fruit surfaces is crucial.

The glassy-winged sharpshooter can be a vector for Pierce's disease, an incurable bacterial disease that will generally kill a grape vine within two years of infection. This publication discusses how kaolin clay particle film can be sprayed to a place a barrier between the pest and its host plant, and offers spraying recommendations.

Table of Contents

• What is Kaolin and How Does it Work?
• Spraying Reccomendations
• A Systems Approach
• Further Resources

California vineyards are facing the combination of an old threat and a new vector—Pierce’s disease, a xylem-clogging bacterial disease which was first identified over 100 years ago, now has a new and efficient vector, the glassy-winged sharpshooter (GWSS) Homalodisca coagulata. Pierce’s disease is incurable and will generally kill a vine within two years of infection. It has a very wide host range (over 170 hosts), and it’s feared that it may already be present in most areas of California, representing a potential time bomb that may explode with the appearance of an efficient vector, such as the GWSS.

A native of the southeast U.S. and first found in Ventura County in 1990, the GWSS is a strong flier, able to travel distances of a quarter mile or more. Other vectors of Pierce’s disease include the blue-green, smoke tree, green, and red-headed sharpshooters. Other crop diseases caused by the Pierce’s disease bacterium (Xylella fastidiosa) include: almond leaf scorch, phoney peach disease, alfalfa dwarf, oleander leaf scorch and citrus variegated chlorosis.

Compared to the GWSS, the blue-green sharpshooter is a poor flier and a much less efficient disease vector. Because of its voracious feeding behavior and high mobility, management of the GWSS will depend on the integration of several tactics, including biological control, vegetation management, monitoring, and other strategies.

What is Kaolin and How Does it Work?

Homalodisca coagulata. Its transparent wings give the glassy-winged sharpshooter its common name. Reprinted with permission. See endnote

A relatively new technology, kaolin sprays are currently available under the tradename Surround® WP Crop Protectant. Please note that Surround is, at this point in time, the only kaolin product suitable and registered for horticultural use. The kaolin in Surround is processed to a specific particle size range, and combined with a sticker-spreader. Non-processed kaolin clay may be phytotoxic. We have heard of one apple grower who bought a traincar load of “generic” kaolin clay, and killed most of his apple trees!

Surround presents a unique form of pest control: a non-toxic particle film that places a barrier between the pest and its host plant. The active ingredient is kaolin clay, an edible mineral long used as an anti-caking agent in processed foods, and in such products as toothpaste and Kaopectate. There appears to be no mammalian toxicity or any danger to the environment posed by the use of kaolin in pest control.

Surround is sprayed on as a liquid, which evaporates, leaving a protective powdery film on the surfaces of leaves, stems, and fruit. Conventional spray equipment can be used, and full coverage is important. The film works to deter insects in several ways. Tiny particles of the clay attach to the insects when they contact the plant, agitating and repelling them. Even if particles don’t attach to their bodies, the insects may find the coated plant or fruit unsuitable for feeding and egg-laying. In addition, the highly reflective white coating makes the plant less recognizable as a host.

Surround has proved to be a very effective management tool for most species of leafhoppers, including the sharpshooters. Results from research conducted in California on GWSS control in lemon are very promising. In grapes, the combined effect of “disguising” vines and interfering with feeding and probing behavior should make transmission of the Pierce’s disease bacterium less likely on Surround-treated surfaces, but this needs to be confirmed by ongoing research in California.

The particle spray was developed by Drs. Michael Glenn and Gary Puterka of the USDA/ARS at Kearneysville, WV, in cooperation with the Engelhard Corporation, which began marketing the product in 1999 on a limited basis, after several years of trials with grower-collaborators. Surround is now available across the U.S., and is listed by the Organic Materials Review Institute (OMRI) for use in organic production.

The glassy-winged sharpshooter is shown next to the smaller blue-green sharpshooter. Reprinted with permission. See endnote

Although at first glance the film may appear to block light, Surround actually increases net photosynthesis, and can provide secondary benefits to the plants’ overall health. Surround keeps the plants cool so that photosynthesis can continue longer into the afternoon on hot days, after untreated plants have already shut down because of heat stress. Grapes treated with Surround show improved vigor and studies have shown positive effects on juice flavor.

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Spraying Reccomendations

• Thorough coverage is key for protection.
• Sprays before expected infestation are much more effective.
• Normal air-blast and hand-held sprayers (but not backpack sprayers) are preferred.
• Re-apply to cover new growth and after heavy rains.
• Re-sprays most important on young fruit.
• Wine grapes sprayed up to veraison will have minimal adherence to berries. Applications after veraison will adhere better to grape berries. Applications may be made up to two weeks before harvest, then continued post harvest. If you are uncertain about Surround residues on grapes, it is recommended to spray only up to veraison.
• Table and raisin grapes—A supplemental label enables applications up to 5 mm berry size; then sprays may be continued post harvest. Applications are not recommended between 5 mm and harvest in order to avoid unsightly residues on harvested fruit.
• For targeted control of glassy-winged sharpshooter: apply during the dormant period up to 5 mm berry size to prevent sharpshooter movement into vines.

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A Systems Approach

Inadequate coverage on pear leaves.

Surround will be most effective when used within a well-managed agro-ecological system combining the most appropriate cultural and chemical methods for the specific vineyard situation, pest complex, and local climate. Such a system will integrate soil building, habitat for beneficial organisms, and well-tuned nutrient and water management.

Wiped leaf...excellent coverage.

Soil building and nutrient/water management are two sides of the same coin and could be considered preventative pest management. A healthy soil high in organic matter will have better water and nutrient holding capacity. Plants receiving too much or too little of either water or nutrients, particularly nitrogen, are more attractive and more susceptible to damage by insects and diseases. Good water management, through water-stress monitoring, conserves valuable (and expensive) soil nutrients, reduces contaminated runoff, and conserves water.

Glassy-winged sharpshooters lay eggs on the under-sides of leaves, usually in groups of 10 to 12. The egg masses appear as small, greenish blisters. These blisters are more easily observed after the eggs hatch, when they appear as tan to brown scars on the leaves. Reprinted with permission. See endnote Parasitized egg masses are tan to brown in color with small, circular holes at one end of the eggs. Reprinted with permission. See endnote

Providing habitat for beneficial organisms is like hiring millions of helpers whose sole aim in life is to eat pests. Nitrogen-fixing cover crops can do double duty as habitat for beneficial organisms if managed correctly.

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Further Resources

Surround® WP Manufacturer:
Engelhard Corporation
101 Wood Avenue
P.O. Box 770
Iselin, NJ 08830-0770
732-205-5000
877-240-0421 (toll-free)
732-321-1598 FAX

Several researchers are examining different facets of GWSS management. Many of them may be contacted through information listed at: http://www.ucr.edu/news/gwss/

Following is contact information for a few of the researchers working on GWSS and Pierce’s disease.

Gary Puterka
304-725-3451
GPuterka@afrs.ars.usda.gov
Gary has researched kaolin clay particle film barriers for control of leafhoppers on pears and is a member of the Kern County GWSS Task Force.

Beth Grafton-Cardwell
559-646-6591
bethgc@uckac.edu
Beth is researching tactics for managing GWSS in citrus in the context of slowing movement from citrus into grapes. The GWSS is not considered a pest of citrus.

Matthew Blua
909-787-6301
matthew.blua@ucr.edu
Matthew is also researching tactics to prevent or slow movement of GWSS into vineyards. He has found that 95% of GWSS fly at 5 meters or lower. He is investigating effects of physical barriers combined with pesticide treatments on the transmission of Pierce’s disease to vineyards.

Alexander Purcell
510-642-7285
purcell@nature.berkeley.edu
Alexander is looking at vegetation management as a strategy for managing the blue-green sharpshooter, the primary vector of Pierce’s disease along coastal areas. This strategy revolves around removing the five or six plant species in any given riparian habitat that the sharpshooter is attracted to during its egg-laying period. This strategy can potentially increase biodiversity and reduce the need for insecticide use.

Bruce Kirkpatrick
530-752-2831
bckirkpatrick@ucdavis.edu
Bruce is knowledgable about host range of Pierce’s disease, as well as diseases and symptoms caused by the bacterium in other hosts.

Mark Hoddle
909-787-4714
mark.hoddle@ucr.edu
or
Dave Morgan
909-787-4360
dmorgan@citrus.ucr.edu
The wasp Gonatocerus triguttatus is successfully reducing populations of the sharpshooter in Mexico and Texas. The wasp parasitizes the sharpshooter by laying its eggs inside those of the larger insect. Once hatched, the wasps eat their way out.

Pierce’s Disease
Pierce's Disease is a concise and authoritative handbook on the disease, its spread, and strategies for containing it. The publication is written by UC scientists on the forefront of the battle. The 20-page publication, produced by the UC Division of Agriculture and Natural Resources (ANR Publication 21600), is priced at $6 a copy, plus tax and shipping, with discounts available for purchases of 10 or more.

Pierce’s Disease is available at local UC Cooperative Extension offices or directly from:
ANR Communication Services
6701 San Pablo Avenue
2nd Floor
Oakland, CA 94608-1239
800-994-8849
510-643-5470 FAX

Kaolin Clay for Management of Glassy-winged Sharpshooter in Grapes
By Rex Dufour
NCAT Agriculture Specialist
Tiffany Nitschke, HTML Production
IP 175
Slot 156

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