History

• Bt's effect as an insecticide was discovered early in the 1900s. During the 1950s, it was developed into a commercial product. The first Bt product arrived on the market in 1961 to control caterpillars in agricultural crops.
  
  

Effect

• The strain of Bt used as an insecticide kills leaf- and needle-feeding caterpillars. When caterpillars ingest Bt, the insecticide releases a toxin that kills the lining of the pest's gut, paralyzing the digestive system. The caterpillar stops feeding and eventually dies of starvation. The process takes several days. Bt is a targeted insecticide. It is not considered a threat to humans, animals and other non-target species.
  
  

Products

• Bt is used by farmers and home gardeners. Several products are available as sprays in garden stores. Look for the active ingredient "Bacillus thuringiensis, var. kurstaki" on labels.