|Shapiro Ilan, David|
Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 10/25/2006
Publication Date: 1/2/2007
Citation: Shapiro Ilan, D.I., Stuart, R.J., Mccoy, C.W. 2007. Longevity of insect-killing nematodes in soil from a pecan orchard. Pecan Grower. 18(3):14-16. Interpretive Summary: Insect-killing nematodes occur naturally in pecan orchards and are being evaluated as potential control agents for pecan weevil, which is a key pest of pecans. WThese particular nematodes only kill insects and are not harmful to humans or the environment. When using these nematodes as biological control agents they are usually applied directly to soil where the insect pest dwells. One important factor in deciding which nematode would be the best one to use to control pecan weevils or other pests is the ability of the nematodes to persist in soil. In this study we compared the persistence of 29 different strains (kinds) of nematodes in soil that was obtained from a pecan orchard. We discovered that the nematode longevity in the soil varies greatly. Two nematodes, called Steinernema carpocapsae (Sal) and Steinernema diaprepesi were found to be the most persistent. These nematodes will be evaluated further for their ability to control pecan weevil and other pests.
Technical Abstract: Entomopathogenic (insect-killing) nematodes are candidates for use as biological control agents for important pecan insect pests such as the pecan weevil, Curculio caryae. In deciding which kind of nematode (species or strain) is the best one to use, it is important to consider which one is likely to survive the longest in the orchard. Therefore, we compared the longevity of 29 different strains representing 11 entomopathogenic nematode species. A series of five laboratory experiments were conducted over 42 to 56 day periods. The experiments were conducted in soil from a pecan orchard in Byron, GA. Overall, we estimated S. carpocapsae (Sal) and S. diaprepesi to have the highest survival capability. The lowest level of longevity was observed in H. indica and H. marelatus, and H. mexicana. Although nematode persistence can vary under differing soil biotic and abiotic conditions, baseline data on longevity such as those reported herein may be helpful when choosing the best match for a particular target pest. The superior longevity observed in S. carpocapsae (Sal) is especially intriguing because this species has previously been shown to possess superior virulence to pecan weevil relative to other nematodes.