Acarotoxicity of Hirslltella thompsonii Fisher Exudate with Reference to the Hvo-spotted Spider Mite, Tetranychlls urticae Koch


Abstract

The exudate from sporulating culture of the mite-specific fungal parasite Hirsutella thompsonii Fisher was tested for potential acarotoxicity through its effect against different stages of Tetranychus uricae Koch, the two-spotted spider mite. T. urticae eggs treated with the exudate showed very significant reduction (64.6%) in hatching. The exudate exhibited ovicidal effect through desiccation in up to 28 per cent of the eggs. A significant number (38%) of treated eggs remained infact and unhatched even after 4 days of incubation, compared with control (4%). The exudate showcd toxicity to both nymphhs and adults of T. uticae that were fed separately on treated cowpea leaves. A maximum of 33.3 per cent mortality was obtained in nymphs before they turned into adults. Adult mortality increased from 55.6 to 77.8 per cent between the fifth and seventh days of treatment. In the fecundity test, an adult female feeding on exudate-treated leaf could lay only 30.7 eggs compared with 51 eggs laid by the mik feeding on untreated leaf over a period of 7 days. Hatching of those eggs was also lower (18.5%.) in comparison with control (38.3%).

Keywords

Acarotoxicity, Exudate, Llirsutella Thompsonii, Tetramychus urticae

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