The effect of varying alkaloid concentrations on the feeding behavior of gypsy moth larvae, Lymantria dispar (L.) (Lepidoptera: Lymantriidae)
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Nine alkaloids (acridine, aristolochic acid, atropine, berberine, caffeine, nicotine, scopolamine, sparteine, and strychnine) were evaluated as feeding deterrents for gypsy moth larvae (Lymantria dispar (L.); Lepidoptera: Lymantriidae). Our aim was to determine and compare the taste threshold concentrations, as well as the ED50 values, of the nine alkaloids to determine their potency as feeding deterrents. The alkaloids were applied to disks cut from red oak leaves (Quercus rubra) (L.), a plant species highly favored by larvae of this polyphagous insect species. We used two-choice feeding bioassays to test a broad range of biologically relevant alkaloid concentrations spanning five logarithmic steps. We observed increasing feeding deterrent responses for all the alkaloids tested and found that the alkaloids tested exhibited different deterrency threshold concentrations ranging from 0.1 to 10 mM. In conclusion, it appears that this generalist insect species bears a relatively high sensitivity to these alkaloids, which confirms behavioral observations that it avoids foliage containing alkaloids. Berberine and aristolochic acid were found to have the lowest ED50 values and were the most potent antifeedants.
KeywordsAlkaloids Feeding behavior Gypsy moth Lymantria dispar Deterrence Gustation Antifeedant Lepidoptera
We gratefully acknowledge Dr. Thomas Heinbockel, Howard University College of Medicine, Washington, D.C. for critically reviewing this manuscript. Many thanks to Mr. Howard Kaplon and Dr. Joel Snodgrass for guidance with the statistical analyses. We also thank USDA-APHIS, Otis Air National Guard Base (Falmouth, Massachusetts) and Robert Bennett (USDA, Beltsville, MD) for kindly supplying us with egg masses and Janelle Akomah for helping with this project. This work was supported by NIH grant 1R15DC007609-01 to V.D.S. and NIH grant GM-58384.
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