ARS | Publication request: MIXING INSECT DISEASES TO KILL PECAN WEEVILS

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: February 2, 2004
Publication Date: February 14, 2004
Citation: Shapiro Ilan, D.I., Jackson, M.A., Reilly, C.C., Hotchkiss, M.W. 2004. Mixing insect diseases to kill pecan weevils. Pecan Grower. 15(3):10-13.

Interpretive Summary: Insect-killing nematodes are small round worms that cause disease and kill insect pests but do not harm people or the environment. These nematodes are promising natural control agents for suppression of the pecan weevil, which is a key insect pest of pecans. Although these nematodes kill the adult stage of the weevil very well, the larval stage of the weevil appears to be only moderately susceptible to nematode attack. Possibly, the ability of the nematodes to kill weevil larvae would be greater if the nematodes were mixed with other natural diseases. We studied the effects of combining an insect-killing fungus or bacterium with nematodes on the ability to pecan weevil larvae. Most of the time when the diseases were applied together they worked against each other causing less weevil mortality. But a few combinations, such as applying the nematode H. indica with the fungus M. anisopliae, appear to have some promise for improving the ability to kill pecan weevils; further research is warranted to explore these promising combinations.

Technical Abstract: Our objective was to determine the effects of combining entomopathogenic nematodes with other entomopathogens on their ability to suppress larvae of the pecan weevil, Curculio caryae. We simultaneously applied the nematodes Heterorhabditis indica or Steinernema carpocapsae with the fungus Beauveria bassiana, Metarhizium anisopliae, or Paecilomyces fumosoroseus, or the bacterium Serratia marcescens. We observed antagonism in all pathogen combinations, except H. indica combined with M. anisopliae, for which additive effects were observed. The combination of H. indica and M. anisopliae may merit further study in other systems.