Associate Professor University of Minnesota Saint Paul, Minnesota
In general, butterfly larvae are less sensitive to three of four insecticides compared to bees. Bees are more sensitive to the neonicotinoids clothianidin and imdacloprid and butterflies are more sensitive to chlorantraniliprole. Third and fifth instar painted lady larvae showed similar ranking of the four insecticides. Monarch fifth-instar larvae are highly sensitive compared to painted lady fifth-instar larvae to all four insecticides. Painted ladylarvae were more tolerant to the two neonicotinoid than adults. Adult painted lady were more tolerant to the two neonicotionids compared to bees. Bifenthrin was similar toxic to bees and adult painted lady butterflies.Residues in greenhouse grown plants at 5 and 10 wks post application are high enough to cause moratality in foraging bumblebees. Pymetrozine killed sucking insects and had no residue at 5 and 10 wks and is a good alternative to use on plants that bees would visit.
Acute LC50s are a reasonable method to compare acute toxicity of pesticides and to rank pesticide toxicity. Chronic rather than acute toxicity values should be compared to field residues, as acute values, only reflect a short exposure. Researchers have noticed that acute studies are usually in the ppm, while field residues and chronic bioassays are often at the ppb level.
