NEMATICIDAL EFFECT OF SUNN HEMP ROOT AND SHOOT EXTRACTS ON EGGS AND SECOND-STAGE JUVENILES OF MELOIDOGYNE JAVANICA

Abstract

Root-knot nematodes (RKN, Meloidogyne spp.) are among the most damaging and widespread nematodes and cause significant yield loss in vegetable production in Florida. Sunn hemp (Crotalaria juncea) is a common, fast-growing leguminous summer cover crop that is also known to be a poor or non-host to RKN. In this study, we investigated the nematicidal effect of sunn hemp plant tissue and extracts on egg hatching and second-stage juvenile (J2) survival of M. javanica under in vitro conditions. Six rates (0, 0.625, 1.25, 2.5, 5, and 10 g/L) of the shoot and root extracts were tested and hatching evaluations were made at 7, 10, 14, 21, and 28 days after treatment. Extract from the shoot was found to have an inhibitory egg hatching effect at 10 g/L, while root extract did not inhibit egg hatch. Second-stage juvenile survival was tested using shoot and root fresh tissue at six rates (0, 1, 5, 10, 15, and 20 g/200 ml soil) under aerobic and anaerobic conditions; survival was evaluated seven days after treatment.  Incorporation of shoot and root fresh tissue in soil negatively affected J2 survival in all tested rates under both conditions. Furthermore, J2 survival was more affected by shoot tissue than root tissue. The results suggest that both sunn hemp shoot and roots have nematicidal activity against eggs and J2 of M. javanica.