Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/4/2001
Publication Date: 7/1/2001
Citation: Shapiro Ilan, D.I. 2001. Virulence of entomopathogenic nematodes to pecan weevil adults (Coleoptera: Curculionidae). Journal of Entomological Science. v.36. p.325-328.
Interpretive Summary: The pecan weevil is a devastating insect pest of pecans in the Southeastern United States. Insect-killing nematodes are natural pesticides that may represent an environmentally friendly solution to the pecan weevil problem. In previous research, the susceptibility of the larval stage of pecan weevils to nematode infection was found to be poor or moderate, and until now, other stages of the weevil were not tested. The objective of this study was to investigate the susceptibility of adult stage pecan weevils. Five different nematodes were tested to determine which might be the best candidate to control pecan weevils. One nematode, Steinernema carpocapsae, caused 99 percent control of adult weevils, which was significantly more control than the other nematodes provided. In general adult insects are not as susceptible to nematode infection as larval stages, but we found the opposite trend in the pecan weevil and Steinernema carpocapsae. The results indicate that there may be great potential in a new biological approach to controlling the pecan weevil, i.e., applying nematodes to kill the adult weevils.
Technical Abstract: The pecan weevil, Curculio caryae (Horn) is a key pest of pecans in the Southeast. Entomopathogenic nematodes have been found to have low to moderate virulence toward larvae of C. caryae. Prior to this research, the adult stage of C. caryae had not been tested for its susceptibility to entomopathogenic nematodes. The objective of this research was to determine the virulence of entomopathogenic nematodes toward adult C. caryae. The nematode, Steinernema carpocapsae (Weiser) (All strain), caused 99% control in adult C. caryae, which was significantly greater than all other nematodes tested including Heterorhabditis bacteriophora (Hb and Oswego strains), S. feltiae (Filipjev) (SN strain), and S. riobrave Cabanillas, Poinar, and Raulston (355 strain). All nematodes were capable of reproducing within adult C. caryae and no significant difference in reproduction was detected among nematode species; approximately 6,000 to 50,000 infective juvenile nematodes were produced in each insect. Steinernema carpocapsae was capable of causing high mortality in C. caryae (more than 70%) after only 15 minutes of exposure. In contrast to other weevils, our results indicated adult pecan weevils to be more susceptible to nematode infection than larval stages. The reproductive capacity and high virulence of S. carpocapsae in adult C. caryae, indicate a high potential for control of this pest.