Effect of kaempferol on ecdysteroid titer and oocyte size via tachykinin-4 in cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

The cotton bollworm, Helicoverpa armigera (Hübner) is an important pest of many crops. Here, effects of kaempferol on ecdysteroid titer in the ovaries, hemolymph andoocyte size via tachykinin-4 content of H.armigera were studied. Third instar larvae of H. armigera were fed on artificial diet containing different concentrations of kaempferol for 8 days. Kaempferol had insecticidal activity after 6 days. The highest level of larval mortality was approximately 36% in larvae fed diet containing 10µg/g of kaempferol for 8 days. Competitive ELISA showed that tachykinin-4 titer decreased clearly in the adult female moth's brain and hemolymph which fed on diet containing 5 and10µg/g kaempferol during their larval stage for 8 days. It also decreased ecdysteroid in the ovary and hemolymph of adult female. Moreover, oocyte size was significantly decreased. On the other hand, the injection of tachykinin-4 into the hemocoel not only increased ecdysteroid titer in the ovary but also approximately 1.4 fold increases in oocyte size was observed. In conclusion, feeding on food containing kaempferol decreased tachykinin-4 level in the brain and hemolymph that itself led to decreasing ecdysteroid titer in the ovary and hemolymph. Finally the decrease in ecdysteroid titer resulted in smaller oocytes.