The effectiveness of Beauveria bassiana and Isaria fumosorosea and their combinations with nutrients or oxymatrine in controlling the okra leaf hopper; Amrasca biguttula biguttula (Ishida)

Abstract

This study was conducted to determine the effect of Beauveria bassiana , Isaria fumosorosea   and oxymatrine on the okra leafhopper, Amrasca biguttula biguttula Ishida. The results revealed that the impacts of these agents were related to isolate. The highest mortality rate after 4 days of treatment was recorded to be 32.6 % by commercial isolate, and after 10 days this isolate achieved  75.7% mortality, the local isolate of B. bassiana was the second  by 27.7 and 66.7% mortality after 4 and 10 days respectively , while the percentage of mortality in the case of    I. fumosorosea were   21.2  , and 62.69% after  4  ,  and 10 days respectively . The commercial isolate was the most virulent isolate with a shortest Lt50 (6.01 days), followed by local isolate ( 6.94 days ) and then I. fumosorosea (7.14 days) at the same concentration. Lt50 value decreased from 6.94 days for normal suspension of B.bassiana to 5.9 days by adding 1% glucose 0.1% yeast extract, and for  I. furnosorosea the Lt50 reduction was 6.87 %. Pre-germination conidia for 12 hours after adding nutrients reduced LT50 values from 5.9 to 5.47 days for B.bassiana  and from 6.64 to 5.95 days for  I. furnosorosea .   The synergistic measurement between oxymatrine  and these fungi achieved enhancing in effectiveness but did not reach the significant level. In case of  B.bassiana , there was a slight increase in the mortality rate due to the combined action of the fungus and the pesticide ( 74.3%)   it does not exceed the additive status ( chi square= 0.57) . In a similar case, the results of the combination of the pesticide and  Isaria fumosorosea ( chi square= 0.14).