A kaolin clay product called Surround WP is gaining credibility as a pest and disease preventative for numerous fruit and vegetable crops. Its most common use is on apples, and that’s the subject of the article on the next page. But Surround WP is also being used for other crops since it was approved for use in organic systems last year by the Organic Materials Review Institute. Surround WP is a non-toxic, kaolin clay-based wettable powder that is sprayed on plants, creating a film barrier that protects them from insects and diseases.

Kaolin is a naturally occurring clay, found around the world but especially in the southeast United States. It is inert and doesn’t react with other materials and is insoluble in water, which may require extra washing of produce when it’s harvested. According to the Environmental Protection Agency, kaolin is not expected to cause any health risks to people, including children. Kaolin has been extensively tested and no evidence of toxicity to humans has been detected. Human exposure occurs primarily through non-pesticidal uses of kaolin. It is used as a packaging ingredient for dry foods, and as an anti-caking agent. It is used in toothpaste and antiperspirants, as well as cosmetics. EPA also found that kaolin is not harmful to non-target organisms or the environment. Studies with spider and honeybees indicate that kaolin appears to have no adverse effects on them.

Kaolin-based products work by putting a thin film of clay between the plant and potential pests. Full coverage is essential to prevent insect damage. Surround WP is approved for use on beans, beets, collards, eggplant, potatoes, peppers, tomatoes, citrus fruits, apples, apricots and berries. The manufacturer, Engelhard Corporation, says it has been effective against cucumber beetles, leaf hoppers and flea beetles. Japanese beetle prevention is also promising,said John Mosko of Engelhard, and research is beginning into use of the product for Colorado Potato Beetle protection. The most popular use, besides apples, is to prevent sunburn on tomatoes. It also is being tested as powdery mildew prevention on pumpkin plants. Richard Earle, an ATTRA program specialist, said that kaolin was widely discussed at a recent conference of organic fruit growers.

Many growers were pleased with the results of Surround but others found problems including a need to reapply frequently during rainy periods. Some growers disliked having their plants all white. Earle stressed that raw kaolin should not be used on plants because it is phytotoxic. The kaolin in Surround WP, he said, is processed to a very fine particulate size and combined with a sticker-spreader. He has heard of one grower who bought a traincar load of raw kaolin clay, sprayed it on his apple orchard and ended up killing most of his trees.

Surround WP is available from many farm supply stores. It costs about $75 an acre for one application, and reapplication is required every 7 to 21 days. For more information, contact Engelhard at 877-240-0421.