Evaluation of organic formulations against Ralstonia solanacearum causing bacterial wilt of solanaceous crops.

摘要

The efficacy of five neem-based formulations viz., Wanis, Spictaff, Neemgold, Neemazal and Achook were evaluated each at 10, 25, 50 and 100% conc in vitro and at 100 and 50% conc in vivo against tomato, brinjal and capsicum isolates of Ralstonia solanacearum causing wilt of these crops. In vitro evaluation was done by paper disc, spectrophotometer and plate count methods. Of the five organic formulations, maximum inhibition zone against all the isolates at 100% conc was observed in Wanis whereas the spictaff formed the least inhibition zone. Streptocycline, copper oxychloride and their combination showed lower inhibition zones than Spictaff in all the concentrations. Wanis with lower OD and corresponding lower cfu ml-1 at all the four concentrations was most inhibitory followed by Achook and Neemgold. Spictaff with highest colony count was least effective against all the three isolates of R. solanacearum. The in vitro evaluation of neem-based formulations showed that Wanis at 100% showed maximum survivability of 14.67 d followed by Achook and Neemazal with 14.33 and 13.67 d, respectively. In vivo test was done by dipping 20-25 d old seedlings in the above suspensions for different durations i.e. 10 and 30 min, 1, 6 and 12 h. Under in vivo test Wanis showed maximum survivability of 14.00 d followed by Achook (13.00 d) and Neemazal (11.67 d) at 100% cone at 1 h dip in tomato isolate. With decreasing order of concentration and dip duration, the survivability also decreased correspondingly in all the treatments when evaluated against brinjal and capsicum isolate.