EXPLOITATION OF NEMATICIDAL POTENTIAL OF BIO AND SYNTHETIC CHEMICALS AGAINST ROOT-KNOT NEMATODE, MELOIDOGYNE INCOGNITA ON TOMATO

Abstract

Root-knot nematode, Meloidogyne incognita is the most widespread and destructive pathogen of tomato as it is difficult to control due to its wide host range. Management strategies for root knot nematodes mainly rely on chemicals/nematicides because of limited availability of resistant cultivars. The present investigation was planned to exploit the nematicidal potential of bio and synthetic chemicals against M. incognita on tomato. The effect of twenty chemicals currently available in the market was evaluated against M. incognita. Hatching inhibition and juvenile’s mortality of M. incognita was assessed under in vitro conditions. Four concentrations of each chemical were prepared viz., 2S, S, S/2 and S/4 according to recommended dose of each chemical. Data on hatching inhibition were recorded after 2, 4 and 6 days and on mortality after 12, 24, 48 and 72 hours of incubation. Maximum hatching inhibition and mortality percentage was recorded in synthetic (Cartap, Virtako) and bio (Cure, Azadirachtin) chemicals. These four chemicals were selected and evaluated further against mobility of juveniles and for their phytotoxic effect on tomato. The minimum number of J2s was recovered in Cartap followed by other chemicals while the maximum was recovered in control. Tomato plants were examined for yellowing or browning, wilting, necrosis, burning and plant mortality for up to two weeks; none of the chemical was found to be phytotoxic. Efficiency of selected chemicals was evaluated at different time intervals viz., 7, 14 and 28 days against M. incognita on nematode reproduction parameters. A gradual decline was noted in the effectiveness of chemicals with the increase in time interval. Galling index was increased in all the chemicals after 28 days interval as compared to 7 and 14 days. Selected chemicals significantly reduced invasion and subsequent development of nematodes in roots. Protective application of selected bio and synthetic chemicals was more effective at nematode suppression rather than being curative. Systemic effect of chemicals was determined through split root technique. Selected chemicals showed systemic activity in terms of lesser number of egg masses, females and eggs/egg mass in the untreated root portion. Selected chemicals were tested as soil drench and root dip treatment against M. incognita. Results revealed that soil drench treatment was more effective in reducing nematode population than root dip treatment. Combined application of selected chemicals with fertilizers not only reduced nematode reproduction but also improved plant growth. Significant suppression in nematode population was observed in all the selected chemicals when applied in infested microplots. The results of present investigation suggest suitable chemicals for growers having a nematode problem in their fields to incorporate it in management strategies.