Preliminary Studies On The Resistance Development Of Spodoptera Exigua (H(?)bner) To Tebufenozide

Tebufenozide as a new biomimetic insecticide has been widely used in the pest resistance management and integrated pest management in the world at present. It has many advantages, such as safe and no toxicity tohuman and animals, no pollution to the environment and the special action mode of stimulating larvae of Spodoptera exigua to molt. Studies carried out in this paper included bio-assay of serial insecticides tebufenozide, methoxyfenozide ect. to S. exigua in the laboratory, sublethal effect of tebufenozide on offsprings of S. exigua, the resistance selection and resistance recession of 5. exigua to tebufenozide , and effects of tebufenozide on the activities of polyphenoloxidase, glutathione-S-transferase, superoxide dismutase, catalase, true choline esterase and esrerase isoenzymes in S. exigua . Main results are as following:1. Comparison of the bio-assay of eight insecticides to the susceptible strain of S. exigua by inoculating larvae with poisonous artificial feedstuff, indicated that tebufenozide and methoxyfenozide had high toxicity to 3rd larvae. The LC50 were 0.14 mg/kg and 0.1 mg/kg respectively.2. The bio-assay of tebufenozide to the eggs of S. exigua was studied by inoculating eggs with poisonous solution, the results showed that hatching rate of eggs had positive correlation with inoculation concentration of tebufenozide, dipping time and relative sensitivity of 5. exigua3. The sublethal effect of tebufenozide on offsprings of 5. exigua was investigated by inoculating larvae with poisonous artificial diet and adults with poisonous solution, the results indicated that tebufenozide had strong after effect and persistece. Tebufenozide had great influence on egg production of 5. exigua. Take the first selection larvae with 0.4 mg/kg tebufenozide for example, total egg production per female of the first and second generations decreased compared with larvae of the susceptible strain 36.49% and 16.75%. The successive adult selection with 0.4 mg/kg tebufenozide, the first,second and fourth generations decreased 20.91%,19.40% and 35.82% respectively. Meanwhile, tebufenozide had less effect on egg hatching rate but significant inhibition to pupation rate and emergence as well as higher abnormal pupae and adule rates. Contemporary pupation rate, female emergence, male emergence, abnormal female adult rate and abnormal male adult rate of larvae treated with 0.4 mg/kg tebufenozide were 4.5%, 74.29%, 68.92%, 18.46% and 19.51% respectively. The effects of tebufenozide on adults were less than the larvae, but theeffects were stronger with the more times and doses.4. The 24h, 48h and 72h activities of polyphenoloxidase, glutathione-S-transferase, superoxide dismutase, catalase, true choline esterase and esrerase isoenzymes in vivo in susceptible strain of 5. exigua and 3rd larvae with 0.14 mg/kg tebufenozide were measured. The results in 3rd larvae with 0.14 mg/kg tebufenozide , showed that polyphenoloxidase activities decreased 79.12%, 10.54% and 56.23% respectively; Superoxide dismutase activities increased 71.59%, 63.16% and 79.55% respectively; Glutathione-S-transferase activities increased 41.43% after 48h but no differences after 24h and 72h; the activities of catalase and true choline had no differences.5. The activitiesof polyphenoloxidase, glutathione-S-transferase, superoxide dismutase, catalase, true choline esterase and esrerase isoenzymes in vivo in susceptible strain of 5. exigua and in Wuhan natural strain of 5. exigua were measured, The results in Wuhan natural strain, showed that polyphenoloxidase activity decreased 38.47% ,significant differences; glutathione-S-transferase activity increased 34.20%, significant differences ; the activities of superoxide dismutase, catalase and true choline esterase had no difference.6. PAGE esrerase isoenzymes of Wuhan susceptible strain, selection strain and natural strain of 5. exigua were determined. The results indicated that there were significant differences in numbers, location, width and visibility of the bands. The map of Wuhan susceptible strain had 15 bands. The 2nd, 12th and 13th bands were slim but poor; 5th and 6th, 7th and 8th were too close to separate. The map of Wuhan nature strain had 10 bands. The 1st, 4th and 9th bands were slim but visible; 6th, 7th 8th and 10th were difficult to visible. The 1st bands had different location compared with the other strains. The map of selection strain had 10 bands. The 1st, 7th and 8th bands were difficult to visible; 3rd and 4th, 5th and 6th were close. The resistance of S. exigua to tebufenozide may be related to esrerase isoenzymes.