Compatibility of Beauveria bassiana Spores with a Sprayable Bioplastic Formulation for Application in the Biocontrol of Tarnished Plant Bug in Cotton

Two isolates of Beauveria bassiana (Balsamo) Vuillemin including the commercial strain GHA and the Mississippi Delta native NI8 strain, and two emulsifiers, tween-80 and a starch-based sprayable bioplastic, were evaluated in the field for pathogenicity and infectivity against the tarnished plant bug (TPB), Lygus lineolaris (Palison de Beauvois). The effect on fruit damage based on within-season cotton plant mapping also was examined. Plots sprayed with B. bassiana showed at least a 2-fold decrease in TPB adults 3-d after treatment compared to control plots. Little to no variation was observed in TPB nymph populations between treated and untreated plots, suggesting that B. bassiana does not affect early stages of TPB. Within-season plant mapping provided clear evidence of damage to cotton caused by TPB. The highest percentage retention of all first position fruiting structures was observed in plots treated with NI8+tween-80 (93.41±1.51) followed by NI8+bioplastic (90.25±1.52). Both treatments were significantly different when compared with GHA+tween-80 (82.89±2.26) and GHA+bioplastic (70.48±3.19), and both GHA formulations did not differ from the control (63.61±2.96). Overall, these results indicated that B. bassiana application resulted in >50% mortality of TPB regardless of the isolates by direct spray or by contact. However, the superior performance of the Mississippi Delta native strain NI8 was observed in all treatment applications and evaluation times. The compatibility of bioplastic with all treatments should make this product an attractive alternative to use with native B. bassiana for TPB control.