Laboratory and field investigations on compatibility of Beauveria bassiana spores with a sprayable bioplastic formulation for application in the biocontrol of tarnished plant bug in cotton

Authors: Portilla, Maribel; Abbas, Hamed; ACCINELLI, CESSARE - University Of Bologna, Italy; Luttrell, Randall

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2018
Publication Date: 12/17/2018
Citation: Portilla, M., Abbas, H.K., Accinelli, C., Luttrell, R.G. 2018. Laboratory and field investigations on compatibility of Beauveria bassiana spores with a sprayable bioplastic formulation for application in the biocontrol of tarnished plant bug in cotton. Journal of Economic Entomology. 112(2):549-557. https://doi.org/10.1093/JEE/toy382.
DOI: https://doi.org/10.1093/JEE/toy382

Interpretive Summary: The entomopathogenic fungus Beauveria bassiana is usually applied in the form of spores, which need stabilizing agents to facilitate application, stability, and enhancement of activity. Oil based emulsion formulations are superior spray carriers with increased probability of direct contact between fungal spores and host insects. Tween-80 has been shown to enhance the production of enzymes such as cellulose, amylase and lignase. It has also been shown to be an activator of fungal spores, making it indispensable for laboratory bioassays and field trials. More recent studies have explored the feasibility of using a bioplastic-based formulation as a carrier of microbiological agents, including atoxigenic isolates of Aspergillus flavus, Link and Trichoderma spp. Therefore, this study was carried out under laboratory and field conditions to evaluate the feasibility of a sprayable bioplastic formulation for carrying spores of the B. bassiana strain NI8 and of the commercial strain GHA spores, in the biocontrol of TPB in cotton.

Technical Abstract: 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 laboratory and field for pathogenicity and infectivity against the tarnished plant bug (TPB), Lygus lineolaris (Palisot de Beauvois). The effect on fruit damage based on within-season cotton plant mapping also was examined. The highest mortality 10-d after treatment was found with insects caged on cotton terminals sprayed with NI8+Tween-80, followed by those exposed to NI8+bioplastic. Similarly, sporulation was shown to be higher in NI8+Tween-80 than in other treatments. 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. 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.