Using good nematodes to kill bad nematodes: Applications of entomopathogenic nematodes for control of the pecan root-knot nematode

Authors: Shapiro Ilan, David; Nyczepir, Andrew

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 5/26/2008
Publication Date: 6/1/2008
Citation: Shapiro Ilan, D.I., Nyczepir, A.P. 2008. Using good nematodes to kill bad nematodes: Applications of entomopathogenic nematodes for control of the pecan root-knot nematode. Pecan Grower. 20(1):36-39.

Interpretive Summary: Nematodes are small round worms. Some nematodes are considered pathogens because they cause disease in animals or plants, whereas other nematodes are considered beneficial because they attack and kill insect pests and are used as natural pesticides. Research indicates that sometimes the good (beneficial) nematodes can also suppress the bad (pathogen) nematodes. We tested whether or not the good nematodes might be able to control a pathogenic nematode called the pecan root-knot nematode. The pecan root-knot nematode was discovered relatively recently and has been shown to be associated with mouse-ear and pecan replant disorder in commercial pecan orchards in Georgia. Our experiments were conducted in the greenhouse using potted pecan seedlings. Results indicated that the good nematodes, or the bacteria that are naturally associated with the good nematodes, have some suppressive abilities toward the pecan root-knot nematode. The results, however, were variable and therefore further research is required to enhance the suppressive effects.

Technical Abstract: Meloidogyne partityla is a nematode parasite of pecan and walnut. Our objective was to determine interactions between the entomopathogenic nematode-bacterium complex and M. partityla. Specifically, we investigated suppressive effects of Steinernema feltiae and S. riobrave applied as infective juveniles and in infected host insects, as well as application of S. feltiae’s bacterial symbiont, Xenorhabdus bovienii. In two greenhouse trials, the treatments were applied to pecan seedlings that were simultaneously infested with M. partityla eggs. After four months plant growth and M. partityla populations were assessed. Although the bacteria treatment as well as the steinernematid treatment applied in infected hosts caused some suppression of M. partityla (up to 80% suppression) and improvement in plant growth, the effects observed were variable. Nonetheless, due to a lack of alternatives, and the fact that at least some suppression effects were observed, additional studies are warranted toward enhancing the suppressive effects.