Survival of Meloidogyne javanica during the summer season under semiarid conditions

One of the survival mechanisms of root-knot nematodes (Meloidogyne spp.) in the absence of host plants during hot and dry summer seasons is anhydrobiosis of second-stage juveniles (J2). Another strategy might be migration of J2 to deeper soil to avoid high soil temperatures and low humidity. Wetting infested soil during such seasons is sometimes suggested as a nematode control method that prevents anhydrobiosis, leading to exhaustion of their energy reserves. Population densities of Meloidogyne javanica at five soil depths (0–50 cm) in irrigated and nonirrigated field plots were estimated during three summer months in two successive years after uprooting infected tomato plants. The number of J2 in the soil was estimated by counting J2 extracted by Baermann funnel extraction and number of root galls on lettuce seedlings grown in the soil samples. Significant factors for J2 survival were number of days after plant removal and soil depth, probably due to lower maximum daily soil temperatures and higher water contents at depth. Irrigation did not consistently affect the number of extracted J2 or root galls. No obvious evidence of J2 migration from the upper to deeper soil layers or nematode-control effects of the irrigation were observed.