Combined Activity of Saponin B Isolated from Dodonaea viscosa Seeds with Pesticide Azadirachtin against the Pest Spodoptera litura

Azadirachtin is regarded as one of the best botanical pesticides due to its broad spectrum of insecticides and low interference with natural enemies. To enhance the effect of azadirachtin and slow down the generation of resistance, the combined activity was studied. Here, we found that Dodonaea viscosa saponin B (DVSB) isolated from the seeds of Dodonaea viscosa has good combined activity with the azadirachtin. The mixture of DVSB and azadirachtin in a volume ratio of 1:4 had the strongest combined effect against Spodoptera litura, with a co-toxicity coefficient (CTC) of 212.87. DVSB exerted its combined activity by affecting the contact angle, surface tension, maximum retention and cell membrane permeability. When mixed with DVSB, the contact angle and surface tension decreased by 30.38% and 23.68%, and the maximum retention increased by 77.15%. DVSB was screened as an effective combined activity botanical compound of azadirachtin upon the control of S. litura and highlights the potential application of botanical compounds as pesticide adjuvants in the pest management.