Insecticidal and inhibitory effects of dihydrobenzofuran neolignans on Bemisia tabaci

Abstract

Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae) has developed resistance to numerous conventional insecticides, which has led us to investigate the toxicity of ten dihydrobenzofuran- (DBN) and benzofuran-type (BN) neolignans structurally related to conocarpan against second instar B. tabaci nymphs. At concentrations higher than 5mg/L, most of the tested compounds killed 100% of B. tabaci biotype B nymphs 6days after spraying. The contact toxicity of compounds 2 ((+/-)-trans-dehydrodiferulate dimethyl ester), 3 ((+/-)-4-O-methyl-trans-dehydrodiferulate dimethyl ester), 5 ((+/-)-4-O-acetyl-trans-dehydrodiferulate dimethyl ester), 6 ((+/-)-7,8-dihydro-trans-dehydrodicoumarate dimethyl ester), 8 ((+/-)-4-O-methyl-7,8-dihydro-trans-dehydrodiferulate dimethyl ester), and 10 ((+/-)-7,8-dihydro-7,8-dehydro-trans-dehydrodicoumarate dimethyl ester) was higher than the contact toxicity of pyriproxyfen at a concentration of 75mg/L, which was used as positive control. Repellent (compounds 2 and 7 ((+/-)-7,8-dihydro-trans-dehydrodiferulate dimethyl ester) and oviposition deterrent (compounds 2, 3, and 7) effects were observed for adult whiteflies exposed to leaves sprayed with DBNs for 24 and 48h, respectively. These results suggest that DBNs have potential application in the development of effective pest management compounds.