The U.S. Environmental Protection Agency has approved registration of a new product for controlling diseases of several crops, including some vegetables and tobacco. Marketed under the name Actigard™, the product works differently than other pesticides.

"This chemical is unlike any other in that it does not directly attack the pathogen, but instead activates, or turns on, certain defense mechanisms that already exist in the plant," said Bill Nesmith, Extension plant pathologist in the University of Kentucky College of Agriculture.

This type of disease control is known as systemic acquired resistance, or SAR. This resistance naturally exists in most plants, but usually fails to give adequate control under natural conditions because it is not activated at the right time. The active ingredient in Actigard™ triggers the plant's defense system prior to disease infection. Subsequently, a chain reaction occurs resulting in compounds in the plant moving to the site where control is necessary.

"Research here at our UK College of Agriculture has focused on this type of disease control for many years," said Nesmith. "Dr. Joseph Kuc, UK emeritus professor of plant pathology, has been a leading researcher in SAR, and I've been extensively involved in field testing in Kentucky, Puerto Rico, Mexico, and other states."

The product has been labeled for use on selected vegetables, such as broccoli and tomatoes, for downy mildew and bacterial disease control. It's also been labeled for controlling tobacco blue mold, which is where it will have its impact in Kentucky. Producers are cautioned to use the product strictly in accordance with labeling instructions to achieve disease control without unacceptable crop injury.

"Our producers need to be aware this is not a magic bullet that will cure all their plant disease problems. It's simply another tool for them to integrate within their total disease management program," Nesmith said. "In our tests it has been highly effective in disease control, but there is almost always a certain amount of phytotoxicity. However, the control benefits and environmental safety off-set the phytotoxicity issues in most cases."

Nesmith said the product has been approved too late for the 2000 growing season, but likely will see significant use this winter for certain vegetables, and next season for vegetables and tobacco.