Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 16, 1999
Publication Date: N/A
Interpretive Summary: The control of insect pests is a perplexing and costly problem for American agriculture. Environmental concerns over the use of chemical pesticides, increasing pressures for the availability of efficient and specific control methods, and international economic competition are problems that demand that agricultural research discover and develop new insect control agents. Parasitic wasps represent an effective natural control for agriculturally important insects, especially lepidopteran larvae which can injure and destroy plants by feeding upon leaves or roots. One of the mechanisms by which these wasps act is the injection of venom into the target insect. The venom can paralyze or kill the insect but is harmless to humans and other animals. We have discovered and partially characterized a component of wasp venom which inhibits gypsy moth larvae from feeding. The component is a protein and is effective at nanogram levels in stopping larval growth. .This discovery presents an opportunity to exploit an endogenous insect molecule, a naturally occurring growth inhibitor, for the specific control of pest insects. This information will be used by researchers in the agrochemical, agricultural biotechnology, and forest industries, who are developing safe, selective methods for insect control.
Larvae of the gypsy moth Lymantria dispar undergo growth inhibition when injected with extract of the venom glands of the adult female ectoparasitic wasp Microbracon hebetor. The inhibition is dose dependent and, at 5 days after injection, growth is inhibited 50 percent by 2 x 10-3 ug venom gland protein per mg larval weight. Doses greater than 3 x 10-2 ug prevent growth completely, leading to larval death. Chromatographic fractions which elute between 35kD and 66kD molecular weigh markers are capable of inhibiting growth, cause larval mortality, and delay pupation. At 7 days after injection, growth is inhibited 50 percent at 4 x 10-4 ug fraction protein per mg larval weight. Crude extract and column fractions each cause their effects without evidence of extended paralysis and without acute toxicity. Inhibition of growth apparently is due to a reduction in feeding activity.