The Sublethal Effects of β-Ecdysterone, a Highly Active Compound from Achyranthes bidentata Blume, on Grape Phylloxera, Daktulosphaira vitifoliae Fitch

Grape phylloxera, Daktulosphaira vitifoliae (Fitch) (Hemiptera, Phylloxeridae), is a very destructive insect pest of grapevines. Intercropping of Achyranthes bidentata Blume (f. Amaranthaceae) and Vitis spp. grapevines can be useful to control this pest. In the present study, the toxicity of 22 compounds, known to be present in A. bidentata, to grape phylloxera was evaluated. All treatments were toxic towards grape phylloxera but the degree of toxicity differed between treatments. Among the 22 tested compounds, several of which proved toxic towards grape phylloxera. However β-ecdysterone had higher toxic effects against grape phylloxera, with LC(50) values of 175.73 mg a.i. liter(-1). In addition, we assessed the sublethal effects of LC(10), LC(20) and LC(40) of β-ecdysterone on grape phylloxera. The fourth instar and adult developmental periods and total life span were significantly prolonged by LC(40) of β-ecdysterone. Fecundity decreased when grape phylloxera were exposed to LC(20) and LC(40) of β-ecdysterone. In addition, LC(40) of β-ecdysterone decreased the intrinsic rate of increase (r(m)) and the finite rate of increase (λ) and prolonged the population doubling time (DT). The net reproductive rate (R(0)) was significantly reduced by both the LC(20) and LC(40) β-ecdysterone treatments. Our results demonstrated that β-ecdysterone had higher toxic effects and significant sublethal effects on grape phylloxera, and showed potential control of grape phylloxera.