Mortality Effects of Beauveria bassiana and Purpureocillium lilacinum Isolates and Efficacy of a Wettable Formulation on Palemona prasina (Hemiptera: Pentatomidae) Nymphs

Abstract

In this study, the mortality effect of two Beauveria bassiana and two Purpureocillium lilacinum isolates on the 4th stage nymphs of Palemona prassiana was determined. The most lethal isolate was formulated as wettable powder and tested on the pest. Furthermore, Y-tube olfactometry tests were conducted to detect behavioral response of the nymphs in presence of the fungus. All the experiments were carried out under controlled conditions. The mortality varied depending on the isolates between 28.51% and 82.14% on the 12th day. Beauveria bassiana FAI-38 caused the highest mortality (82.14% at 1x108 conidia ml-1) with LC50 and LT50 estimations of 3.3x106 conidia ml-1 and 8.4 days, respectively. According to data taken 6 and 12 days after application, the wettable powder formulation was found to be significantly more effective (89.65% at 1x107 conidia ml-1, LT50 6.08 days). According to the Y-tube olfactometry tests, the nymphs exhibited avoidance from unformulated B. bassiana spores; however, once the spores were formulated as wettable powder, the behavior of the insects changed to neutral. It is concluded that Beauveria bassiana FAI-38 presents a potential as a control agent, and the wettable powder formulation of the fungus improves its effectiveness by increasing mortality and removing repellency effect of the fungal spores.