Characteristics of Biopesticides
Biopesticides are quickly emerging as important tools in reducing pesticide use and risk. Pesticide users have expressed such interest in these pesticides that EPA created a special division called the Biopesticides and Pollution Prevention Division, tospeed up the registration of biopesticides. Biopesticides generally exhibit the following characteristics:
* They have a narrow target range and highly-specific mode of action;
* They are slow acting;
* They suppress (rather than eliminate) pest populations;
* Timing of application is relatively critical;
* There is limited field persistence and shelf life;
* They are often used as part of Integrated Pest Management programs;
* They are generally safer to humans and the environment than conventional pesticides; and,
* They usually present no residue problems.
There are two types of biopesticides, biochemical and microbial. Biochemical pesticides are structurally similar to, and functionally identical to, a naturally occurring counterpart, and have a nontoxic mode of action. An example of a biochemical pesticide includes pheromones. Pheromones are naturally-occurring chemicals that insects use to find mates. Chemically synthesized pheromones can disrupt insect mating by creating confusion during the search for mates, or by attracting insects to traps.Microbial pesticides are naturally-occurring or genetically altered bacteria, fungi, algae, viruses, or protozoans that suppress pests by either producing a toxin specific to the pest, causing disease, preventing establishment of pest microorganisms through competition, or other modes of action. Bacillus thuringiensis (B.t.) is an example of a microbial pesticide. B.t. is a naturally-occurring soil bacterium that is toxic to the larvae of several species of insects but virtually nontoxic to nontarget organisms. B.t. is applied foliarly, or incorporated into the genetic material or crops, including B.t. corn and B.t. cotton. About 10-14 million acres of B.t. corn will be available for 1998 nationwide. In 1997, growers planted approximately 2 million acres of B.t. cotton. That number could double in 1998.