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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #257742
Title: Effects of combining microbial and chemical insecticides on mortality of the pecan weevil (Coleoptera: Curculionidae)

Author
item Shapiro Ilan, David
item Cottrell, Ted
item Wood, Bruce

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2010
Publication Date: 2/1/2011
Citation: Shapiro Ilan, D.I., Cottrell, T.E., Wood, B.W. 2011. Effects of combining microbial and chemical insecticides on mortality of the pecan weevil (Coleoptera: Curculionidae). Journal of Economic Entomology. 104:14-20.

Interpretive Summary: The pecan weevil is a key pest of pecans. Current control recommendations are based on chemical insecticide applications, primarily carbaryl and pyrethroids (e.g., cypermethrin). Natural biocontrol agents such as the insect-killing nematode called Steinernema carpocapsae and the fungus named Beauveria bassiana are native to southeastern US pecan orchards and have shown promise as environmentally-friendly alternative control agents for pecan weevil. Conceivably, the chemical and biological agents occur simultaneously within pecan orchards or might be applied concurrently. The objective of this study was to determine the interactions between two chemicals that are used in commercial pecan weevil control (carbaryl and cypermethrin) and the microbial agents B. bassiana and S. carpocapsae. In laboratory experiments, pecan weevil larval or adult mortality was assessed following application of microbial or chemical treatments applied singly or in combination (microbial + chemical agent). The nature of interactions (antagonism, additivity, or synergy) in terms of weevil mortality was evaluated. Results for B. bassiana indicated synergistic activity with carbaryl and antagonism with cypermethrin in weevil larvae and adults. For S. carpocapsae, synergy was detected with both chemicals in pecan weevil larvae, but only additive effects were detected in adult weevils. Our results indicate that the chemical-microbial combinations tested are compatible with the exception of B. bassiana and cypermethrin. Additionally, combinations that exhibited synergistic interactions may provide enhanced pecan weevil control in commercial field applications; thus, their potential merits further exploration.

Technical Abstract: The pecan weevil, Curculio caryae (Horn), is a key pest of pecans [Carya illinoinensis (Wangenh.) K. Koch]. Current control recommendations are based on chemical insecticide applications, primarily carbaryl and pyrethroids (e.g., cypermethrin). Microbial control agents such as the entomopathogenic nematode, Steinernema carpocapsae (Weiser) and the fungus, Beauveria bassiana (Balsamo) Vuillemin are native to southeastern US pecan orchards and have shown promise as alternative control agents for C. caryae. The objective of this study was to determine the interactions between two chemicals that are used in commercial C. caryae control (carbaryl and cypermethrin) and the microbial agents B. bassiana and S. carpocapsae. In laboratory experiments, pecan weevil larval or adult mortality was assessed following application of microbial or chemical treatments applied singly or in combination (microbial + chemical agent). The nature of interactions (antagonism, additivity, or synergy) in terms of weevil mortality was evaluated. Results for B. bassiana indicated synergistic activity with carbaryl and antagonism with cypermethrin in C. caryae larvae and adults. For S. carpocapsae, synergy was detected with both chemicals in C. caryae larvae, but only additive effects were detected in adult weevils. Our results indicate that the chemical-microbial combinations tested are compatible with the exception of B. bassiana and cypermethrin. Additionally, combinations that exhibited synergistic interactions may provide enhanced C. caryae control in commercial field applications; thus, their potential merits further exploration.