The virulence and proteolytic activity of some entomopathogenic fungi isolates, viz., Metarhizium anisopliae, Beauveria bassiana, Verticillium lecanii, and , against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), were evaluated. Common maize plants (Zea mays L.) infested with females of T. urticae were treated in vivo by spraying with suspensions of 1 × 108 conidia ml−1 concentration of selected isolates. Lethal effects of fungal isolates were assessed as percentages of daily mortalities of mites, compared to the mortality in control. Virulence of the fungi isolates was estimated based on the LC50 values calculated by probit analysis for the individuals treated by 1 × 105 conidia ml−1 concentration. Proteolytic activity of isolates was assayed on casein substrate to reflect their virulence towards T. urticae. The mite mortality rates increased with increasing conidial concentrations as well as days after treatment. The mortality rate caused by M. anisopliae isolate varied from 18.75 to 85%, with LC50 value of 4.6 × 105 conidia/ml and LC90 value of 2.4 × 108 conidia/ml during 7 days, respectively. The isolate of B. bassiana caused 15 to 70% mortality, and its LC50 and LC90 values estimated 3.3 × 106 and 7.8 × 109 conidia/ml, respectively. However, V. lecanii isolate caused 11.25 to 72.50% mortality with LC50 of 5.2 × 106 conidia/ml, while T. harzianum was potentially less virulent than other isolates causing 8.75 to 63.75% mortality rate to T. urticae with LC50 of 9.4 × 106 conidia/ml. M. anisopliae showed the highest proteolytic activity at all concentrations, followed by B. bassiana in 3rd, 5th, and 7th day post treatment. These findings recommend the selection of virulent fungal isolates for use as natural and environmentally safe agents in biological control programs to combat mite pests.

中文翻译：

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昆虫病原真菌对两点叶螨Tetranychus urticae Koch（Acari：Tetranychidae）的毒力和蛋白水解活性

评估了一些昆虫病原真菌分离株的毒力和蛋白水解活性，例如，分离的金属异化菌，球孢白僵菌，黄萎病菌以及对两斑的蜘蛛螨Tetranychus urticae Koch（Acari：Tetranychidae）。在体内接种了荨麻疹雌虫的普通玉米植株（Zea mays L.）通过喷洒浓度为1×108分生孢子ml-1选定菌株的悬浮液进行体内处理。将真菌分离物的致死作用评估为与对照组死亡率相比，螨的每日死亡率百分比。真菌分离物的毒力是根据概率分析计算的LC50值估算的，该LC50值是用1×105分生孢子ml-1浓度处理的个体的。在酪蛋白底物上测定了分离物的蛋白水解活性，以反映其对荨麻疹的毒力。螨的死亡率随着分生孢子浓度的增加以及治疗后的几天而增加。在7天内，由分离的支链霉菌引起的死亡率在18.75％至85％之间，LC 50值为4.6×105分生孢子/ ml，LC90值为2.4×108分生孢子/ ml。球孢杆菌的分离物可导致15％至70％的死亡率，其LC50和LC90值分别估计为3.3×106和7.8×109分生孢子/ ml。然而，山核桃弧菌引起的死亡率为11.25％至72.50％，LC50为5.2×106分生孢子/毫升，而哈茨木霉的潜在毒性低于其他分离株，导致荨麻疹的死亡率为8.75至63.75％，LC50为9.4×106分生孢子/毫升。在所有浓度下，分枝杆菌都表现出最高的蛋白水解活性，在处理后的第3、5和7天，其次是球孢杆菌。