دراسة القدرة الإمراضية للفطر Beauveria bassiana (Bals.)‎ Vuil. في بالغات و بيض الحلم العنكبوتي ذو البقعتين Tetranychus urticae Koch تحت ظروف المختبر

Abstract EN

Laboratory studies were conducted to evaluate the pathogenicity of three isolates of the fungus Beauveria bassiana (Bals.) Vuil.

(B3, B2 and B4).

The isolates were used as a suspension at different concentrations (105, 106 and 107 spore/ml), and applied on adults of Tetranychus urticae Koch in the laboratory.

Also, the effect of the two isolates B2 and B4 was studied on eggs and fecundity and longevity of adults of T.

urticae, at 106, 107 and 108 spore/ml concentration.

Results showed high efficacy of the three isolates at all concentrations in killing spider mite adults.

The isolate B2 showed the highest virulence compared with other isolates, and caused mortality that reached 70, 80 and 84% at the concentrations of 105, 106 and 107 spores/ml, respectively, thirteen days after treatment.

The half lethal time (LT50) attained was 7.65, 7.58 and 8.05 days, respectively.

The isolates B4 and B3 caused mortality reached 70 and 78%, respectively, when the concentration of 107 spore/ml was used, and after the same period.

Results also showed that the direct effect of the fungus on egg hatching was not important although it differed significantly compared with the control.

Egg hatching rates were 87 and 90% when the isolates B2 and B4 were used at concentration 108 spore/ml, respectively, compared with 98% for the control treatment on the 3rd day after treatment.

The proportion of mites that were able to complete development to adults, 9 days after egg hatching were 88.66 and 89%, respectively, compared with 100% for the control.

The effect of the fungus on mite females fecundity was obvious.

When the total fecundity attained was 76.8 egg/female in the control, it was 24.2 and 41.3 egg/female, following treatment with 108 spores/ml of the isolates B2 and B4, respectively.

Keywords: Beauveria bassiana, Tetranychus urticae, pathogenicity, total fecundity