Interactions between the Steinernema feltiae Xenorhabdus bovienii insect pathogen complex and the root-knot nematode Meloidogyne incognita

The interactions between a plant-parasitic nematode, Meloidogyne incognita, and an entomopathogenic nematode, Steinernema feltiae, and its associated symbiotic bacterium, Xenorhabdus bovienii, are described. Our objective was to determine the manner in which the presence of the S. feltiae-X. bovieni i nematode-bacterium complex affected infectivity and reproduction of M. in cognito in tomato roots (cv. Rutgers). Tests demonstrated that a common app lication rate of S. feltiae for insect control, 2.5 billion/ha (scaled to o ur laboratory and greenhouse tests), significantly decreased M. incognito g alling, egg production, and egg hatch rate. Two time course experiments wer e conducted against M. incognito with rates of S. feltiae that corresponded to the effective concentrations. In the first time course experiment, M. i ncognito and S. feltiae were applied the same day to tomato seedlings in sa nd. Twelve plants were assessed destructively each week for 6 weeks after i noculation with the two nematode species. Neither M. incognito penetration rate nor developmental rate was affected by S. feltiae application. Egg pro duction per plant and egg hatch rate were significantly reduced in the trea ted plants. However, the number of eggs per egg mass in treatment plants wa s not different from that in control plants. The average number of galls pe r plant 6 weeks after the initial inoculation was lower in the treated plan ts than in the control plants. In the second time course experiment, the sa me rate of S. feltiae was applied to sand in which plants already infected with M. incognita had been transplanted. Development of nematodes inside th e root was not affected by S. feltiae in the sand. Galling 6 weeks after th e application was again less in the treatment than in the control plants. T he presence of the S. feltiae-X. bovienii complex at a density that reflect s the recommended field application rate had suppressive effects on M. inco gnito in these laboratory trials. Our data show that S. feltiae application s decrease M. incognito galling, egg production per plant, and egg hatch bu t not individual female egg production. (C) 2001 Academic Press.