Effects of four host plants on susceptibility of Spodoptera litura (Lepidoptera: Noctuidae) larvae to five insecticides and activities of detoxification esterases.
BACKGROUND
The tobacco cutworm, Spodoptera litura (F.), is one of the most destructive polyphagous pests worldwide. The susceptibility of S. litura larvae reared on tobacco, Chinese cabbage, cowpea and sweet potato to phoxim, chlorfenapyr, methomyl, fenvalerate and emamectin benzoate under laboratory conditions was determined.


RESULTS
Spodoptera litura larvae reared on tobacco were most tolerant to all insecticides, whereas those that fed on sweet potato were most susceptible. When larvae were reared on each host plant for three generations, the susceptibilities to phoxim of larvae that fed on Chinese cabbage and cowpea were similar, whereas the susceptibility of larvae that fed on sweet potato decreased by the third generation, and on tobacco the susceptibility decreased in each consecutive generation. When nicotine was added to their diet for three consecutive generations, the tolerance of larvae to phoxim increased twofold, and to emamectin benzoate 3.1-fold, but the tolerance of larvae to fenvalerate and chlorfenapyr did not change. The acetylcholinesterase activities of the larvae that fed on sweet potato and cowpea were greater than the activities of those that fed on Chinese cabbage and tobacco. In contrast, the carboxylesterase activities of the larvae that fed on tobacco and Chinese cabbage were greater than the activities of those that fed on sweet potato and cowpea. The glutathione S-transferase activities of larvae were highest when they fed on tobacco, followed by Chinese cabbage and cowpea, and the lowest activities were observed when larvae fed on sweet potato.


CONCLUSIONS
Feeding on tobacco or with nicotine added to the diet, the larvae became more tolerant to insecticides, especially to phoxim and emamectin benzoate.
Xue
Ming
M
Department of Entomology, College of Plant Protection, Shandong Agricultural University, Taian, Shandong, China.
Pang
Yun-Hong
YH
Li
Qing-Liang
QL
Liu
Tong-Xian
TX
D000818:Animals; D001937:Brassica / Q000469:parasitology; D004351:Drug Resistance; D004950:Esterases / Q000378:metabolism*; D007887:Fabaceae / Q000469:parasitology; D005982:Glutathione Transferase / Q000378:metabolism; D006790:Host-Parasite Interactions; D007300:Insect Control; D019476:Insect Proteins / Q000378:metabolism*; D007306:Insecticides / Q000633:toxicity*; D027723:Ipomoea batatas / Q000469:parasitology; D007814:Larva / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D010935:Plant Diseases / Q000469:parasitology*; D018411:Spodoptera / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D014026:Nicotiana / Q000469:parasitology; D014675:Vegetables / Q000469:parasitology*
D019476:Insect Proteins; D007306:Insecticides; D005982:Glutathione Transferase; D004950:Esterases