UTTAR PRADESH JOURNAL OF ZOOLOGY

An attempt was made with an insect growth regulator, Tebufenozide (RH-5992) for determining the effect on fruit borer, Helicoverpa armigera Hubner. Tebufenozide is an ecdysterone agonist that induced moulting processes in newly born and fourth instar larvae of the test insect. In newly born H. armigera larvae, RH-5992 at 0.10 ppm to 5.00 ppm influenced larval weight, mortality as well as pupal weight in a dose-dependent manner. In newly born larvae, the average larval weight after 7 days was 64.46 ± 2.82 mg, maximum average larval weight was 325.63 + 7.16 mg and average pupal weight was 197.47 ± 15.36 mg at 0.10 ppm. Tebufenozide was also fed to the fourth instar H. armigera larvae at 1.00 ppm to 20.00 ppm, resulting in maximum larval weight of 468.55 + 19.6 mg at 1.00 ppm and average pupal weight of 188.45 ± 15.4 mg at 1.00 ppm, but at 20 ppm, pupation did not take place, since 100% larval mortality occurred on the 7th day. This study established that 10 to 20 ppm doses of insect growth regulator, RH-5992 induced moulting and disrupted moulting processes. Histopathological effects of Tebufenozide at the light microscopic level in the fourth instar larvae showed completely disrupted peritrophic membrane and lost compactness of columnar cells. At electron microscopic level the midgut showed completely disrupted peritrophic membrane.