Isolation and in vitro screening of Bacillus thuringiensis and clonostachys rosea as biological control agents against sheep nematodes

摘要

Biological control agents are possibly the best alternative to agrochemicals for the control of livestock nematodes. Strains of?Bacillus thuringiensis (Bt)?and?Clonostachys rosea?were isolated from grazing pastures collected from pens of livestock. A total of 25 isolates of?B. thuringiensis?and 10 of?C. rosea?were successfully isolated.?In vitro?studies were conducted to determine the efficacy of?B. thuringiensis?(Bt) and?C. rosea?isolates as biological control agents against sheep nematodes. All of?Bt?and?C. rosea?reduced nematode counts considerably. Isolates of?Bt?and?C. rosea?reduced nematodes counts by 28.5 to 62% and 44 to 69.9%, respectively, in the faeces bioassay. In the water bioassay nematode count reductions of 62 to 85% and 62.7 to 89.3% by?Bt?and?C. rosea, respectively, were observed. Majority of the best nematode-killing isolates were from a goat grazing pasture. Both biocontrol agents showed capability to reduce nematode counts in this study.