Control of Bemisia tabaci and Frankliniella occidentalis in cucumber by Amblyseius swirskii

Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) and Frankliniella occidentalis (Thysanoptera: Thripidae) are major pests in greenhouse grown cucumber crops. Recently, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was shown an effective biological control agent of both pests. Hence, perhaps both pests can be controlled simultaneously by this predator. However, with simultaneous infestation of both pests, synergistic effects, or interference could affect biological control and perhaps require changes in release rates of the predator. Thus, the aim of the present study was to evaluate different release rates of A. swirskii to control both pests under a worst case scenario of rapid immigration into a cucumber greenhouse. Two experiments were conducted, one simulating the influx of whiteflies alone (whitefly experiment) and the other immigration of whiteflies and thrips together (whitefly plus thrips experiment). Three treatments were compared in the whitefly experiment: (1) B. tabaci alone, (2) B. tabaci + 25 A. swirskii m(-2) and (3) B. tabaci + 75 A. swirskii m(-2). The high release rate was more effective than the low rate in controlling B. tabaci alone. The high rate was subsequently tested against B. tabaci and F. occidentalis for the whitefly and thrips experiment in which five treatments were compared: (1) B. tabaci alone, (2) F. occidentalis alone, (3) B. tabaci + 75 A. swirskii m(-2), (4) F. occidentalis + 75 A. swirskii m(-2) and (5) B. tabaci + F. occidentalis + 75 A. swirskii m(-2). This rate of A. swirskii controlled whiteflies and thrips either alone or together. Therefore, 75 A. swirskii m(-2) should be an adequate rate for controlling both pests either alone or simultaneously in cucumber greenhouses.