Development of a diagnostic technique for monitoring permethrin resistance in soybean looper (Lepidoptera: Noctuidae) larvae
1992
Mink, J.S. | Boethel, D.J.
A glass-vial technique was developed to detect permethrin resistance in soybean looper, Pseudoplusia includens (Walker), larvae. Third-, fourth-, and sixth-instar soybean loopers from two susceptible (laboratory) and eight field strains were exposed to permethrin using a glass-vial technique to estimate concentration-mortality lines. Probit analysis of results from each field strain indicated that LC50s for third, fourth and and fifth instars were not significantly different. Therefore, concentration-mortality lines for each soybean looper strain were estimated by pooling data from these three instars. A discriminating concentration of 0.5 microgram permethrin per vial was identified for detection of permethrin resistance in field populations of soybean looper larvae. Field strains from cotton-soybean agroecosystems responded similarly and had higher levels of resistance than strains from soybean-corn agroecosystems. The reliability of the vial bioassay was confirmed by topical bioassays done on the same populations that had been tested in the vials and a comparison of resistance ratios. Correlation analysis indicated that the vial technique was as reliable as topical bioassays in estimating resistance, although resistance ratios with vials were slightly higher at most locations.
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