The Mississippi Department of Agriculture and Commerce requested the exemption for the nonlabeled use of the insect growth regulator to give farmers another management tool to thwart the pests in 2003.The exemption became effective May 15 and expires Sept. 30.

Intrepid, which is manufactured by Dow AgroSciences, causes larvae to undergo a premature molt within hours of ingestion because it mimics the action of a natural insect molting hormone.

The product can be effective against many species of lepidopteran pests, such as armyworms, loopers and caterpillars, without harming beneficial insects, such as lacewings, lady beetles and parasitic wasps.

Saltmarsh caterpillars are often called "wooly bears" because they take on the characteristic "large, hairy" appearance as they voraciously gobble plant leaves to increase their size. Soybean loopers are small light green caterpillars that have a "looping" or measurement movement when they crawl. Armyworms are conspicuous by the stripes along the sides of bodies and distinguishing marks either on the sides or the head.

Loopers and armyworms are also difficult to control because of their resistance to certain insecticides already in use.

"Timing is everything when outbreaks of these pests occur," said Mississippi Agriculture Commissioner Lester Spell. "Hopefully, their effort at controlling pest populations will be helped because this product is available."

The department has authority under Section 18 of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) to obtain an exemption from the United States Environmental Protection Agency for a nonlabeled use of a pesticide if significant losses of an agricultural commodity are likely and alternative, labeled products are not available or effective.

The department's Bureau of Plant Industry has responsibility for administration of the exemptions.