Effects of Eupatorium adenophorum extract on growth, development and reproduction of Spodoptera exigua.
In order to know the influence of extracts from Eupatorium adenophorum to the growth, development and reproduction of Spodoptera frugiperda, the crude extracts of E. adenophorum were diluted to four different concentrations (20-fold, 15-fold, 10-fold, 5-fold) to treat maize leaves before feeding S. frugiperda under laboratory conditions. Afterwards, the instar larvae and pupae development period, survival rate, weight, adult longevity, offspring sex ratio, F2 generation egg hatchability, and developmental period of F2 generation egg were investigated and recorded in this study. The results showed that the developmental period of larvae and pupae of each instar were prolonged with the increase of extract concentration. The pupae held the longest developmental duration under the 5-fold concentration and its duration was reached to 20.27 d, while the larvae had the longest developmental duration and its duration was reached to 21.46 d under 10-fold concentration treatment. The weight of larvae and pupae of each instar decreased with the increase of the treatment concentration, and the survival rate of each developmental stage showed a downward trend. The crude extract had the greatest effect on the survival rate of pupae, and had the least effect on the survival rate of the 1st ~ 3rd instar larvae than other stage. The adult longevity was shortened, and the longevity of female adults was longer than that of male adults with the increase of treatment concentration. With the increase of treatment concentration, preoviposition duration and the developmental period of F2 generation eggs of the S. frugiperd were prolonged. Meanwhile, oviposition duration was shortened, single female oviposition, sex ratio, and the hatching rate of F2 generation eggs were reduced. Overall, the extract of E. adenophorum had negative effects on the growth, development and reproduction of S. frugiperd. It was found that the extract of 5-fold concentration had the most significant effect on the growth, development and reproduction S. frugiperd, it could be used as an important botanical insecticide to control S. frugiperd.