Evaluation of black-eyed susan rudbeckia hirta L. (Asterales: Asteraceae) as an insectary plant for a predacious natural enemy orius sauteri (Poppius) (Heteroptera: Anthocoridae)

Abstract

Black-eyed Susan Rudbeckia hirta L. was evaluated as an insectary plant of a minute pirate bug, Orius sauteri (Poppius). In reinforced greenhouses, we established a treatment plot in which black-eyed Susan growing in planter boxes was arranged along the tomato rows, and a control plot of tomato without black-eyed Susan. O. sauteri and its prey, such as aphids, whiteflies and thrips occurred on the black-eyed Susan from mid-July to late September. On the black-eyed Susan, a relatively high population density of O. sauteri was maintained from mid-August to mid-September even when the population density of the prey was very low. Two species of whitefly, Trialeurodes vaporariorum(Westwood) and Bemisia tabaci(Gennadius) occurred on tomatoes in both plots during the duration of this experiment. The population density of O. sauteri on tomatoes in the treatment plots increased as did that on black-eyed Susan; however, the population density of O. sauteri on tomatoes in the control plot showed no increase throughout the study. The population density of O. sauteri on tomatoes in the treatment plots was significantly higher than that in the control plots(two-factor repeated measures ANOVA, p>0.05). The results indicate that the high density of O. sauteri on tomatoes in the treatment plot is due to immigration of O. sauteri from black-eyed Susan to tomato; however, the difference in the population densities of whiteflies between the two plots was not significant(two-factor repeated measures ANOVA, p>0.05).