Investigating the effectiveness of feeding deterrents against the southern corn rootworm, using behavioral bioassays and toxicity testing
1989
Landis, D.A. | Gould, F.
Leaf-disk feeding tests were conducted to determine the effect of various chemicals on southern corn rootworm, Diabrotica undecimpunctata howardi Barber, larval feeding. Ethanolic extracts of plant seeds from the family Meliaceae were all highly active feeding deterrents, while hexane extracts were ineffective as deterrents. In leaf disk feeding tests, the fungicide thiram (tetramethylthiuram disulfide), as technical material or formulated as thiram 50% or 75% (AI) was also an effective feeding deterrent. In choice tests, all thiram-based deterrents were equally effective, while in no-choice tests, thiram-75 was most effective at preventing feeding. Thiram-75 was also effective in protecting corn seedlings in a soil bioassay mimicking the field environment. It was determined that the formulation of thiram-75 used in these tests had been contaminated with 0.87% dieldrin (by weight). The contaminated thiram-75 had a toxic action, as well as a deterrent effect on southern corn rootworm larvae and both factors contributed to overall feeding inhibition. Toxicity was not found in technical thiram or in thiram-50. The mode(s) of action of the various deterrents are discussed in relation to screening procedures.
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