Economic threshold and economic injury levels for the two spotted spider mite Tetranychus cucurbitacearum (Sayed) on soybean

Abstract

Economic injury and economic threshold levels were estimated for the two spotted spider mite, Tetranychus cucurbitacearum (Sayed) (Acari, Tetranychidae) on soybean plants. An attempt was made to determine, mathematically, the point at which a significant reduction occurs in the yield of soybean at different levels of infestation by the two spotted spider mite, T. cucurbitacearum. For this purpose, counts were taken during each of the main three annual peaks of this mite infestation over two seasons of (2015and 2016). The obtained results indicated that the mean values of economic injury level were 28.97 and 22.01 individuals / leaflet , while mean values of economic threshold levels were 32.05 and 21.23 individuals / leaflet during 2015 and 2016 seasons, respectively, while the general mean of economic threshold and economic injury levels were 21.23 individuals per leaflet and 18.21 individuals per leaflet, respectively.