Comparative toxicity and tolerance for the ecdysteroid mimic tebufenozide in a laboratory and field strain of cotton leafworm (Lepidoptera: Noctuidae)
1997
Smagghe, G. | Degheele, D.
We investigated whether tolerance can be induced after continuous application of the nonsteroidal ecdysteroid mimic tebufenozide at about LC30 over 5 generations of the cotton leafworm Spodoptera littoralis (Boisduval). After 2 and 4 generations, toxicity data showed that such continuous treatment did not result in a shift of insect susceptibility even after 4 generations in S. littoralis, indicating the difficulties in achieving resistance in this pest to tebufenozide. Intoxicated larvae showed signs of premature and lethal molting within 24 h of treatment. In addition, tebufenozide inhibited oviposition which resulted in loss of the specifically treated strain after 5 generations. In a 2nd series of experiments, the potency of the ecdysteroid agonists tebufenozide and RH-5849 against 3rd instars of a laboratory and multiresistant field strain of S. littoralis was compared with the activity of 2 commonly used pyrethroid, organophosphorus, carbamate and benzoylurea insecticides against Lepidoptera. According to LC50, teflubenzuron was the most potent compound, followed by cypermethrin and deltametrin, and tebufenozide. The remaining compounds were 2-100 less effective than tebufenozide. Our results indicate that resistance with tebufenozide is difficult to achieve; however, further research on tolerance and cross-resistance is required before definitive conclusions can be drawn.
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