Clay-based spray aids apple growers.

• Position: Agriculture - Brief Article

A harmless clay-based solution, sprayed on apple trees, can protect the fruit from some diseases and insect pests. Andrew Thomas, a research associate at the University of Missouri Southwest Center near Mt. Vernon, has tested a spray made of kaolin, a nontoxic clay that is so safe it has been approved for human consumption. "If you've ingested Kaopectate, you've eaten kaolin," he points out.

A kaolin-based spray, Surround, was released in 2000 and successfully used to treat pear orchards in the western U.S. "I thought about the potential in Missouri for organic apple production," Thomas explains. "The idea is to use safe materials to coat the plants in order to suppress pests and protect from some disease." In a two-year trial, he tried Surround in different regimens on several different apple orchards. One of the test locales received no treatment. He and his team of student assistants used traps to isolate and identify insect pests in the orchards. "If we didn't find, say, a red-banded leaf-roller, then we'd know that spot on the apple wasn't from one of those."

One pest that was present--and proved to be repelled effectively by the Surround spray--was plum curculio, a common apple worm that Thomas calls "just a nightmare. It can be controlled, but it requires an incredible amount of spraying." In the untreated trees, 80% of the fruit was destroyed by it. In those sprayed with the kaolin-based chemical, the...