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The effect of fungal infection on the reproductive potential of two-spotted spider mite, Tetranychus urticae, was evaluated as part of the full biocontrol potential of three entomopathogenic fungi by modeling of fecundity probability. Female mites (or= 0.98), yielding a solution to the probability for the female mites to achieve a specific fecundity {P(m 10 eggs despite some variation among the tested fungi. In contrast, the chances for the non-infected mites to achieve the low and high fecundities were 23 and 55%. The fitted probabilities provide a full coverage of the fecundity potential of infected versus non-infected mites and are more informative than the mean fecundities.

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The compatibilities of 10 acaricides with Beauveria bassiana SG8702 varied significantly in 24 h liquid cultures including three chemical rates. Pyridaben, hexythiazox and propargite were found highly compatible with the fungus even at field application levels. Four bioassays were performed with Tetranychus cinnabarinus eggs using a non-touch leaf method. The Յ18 h-old eggs laid on detached fava bean leaves were exposed to gradient conidial sprays of B. bassiana alone in Assay 1 or together with the pyridaben rates of 0.05, 1.0 and 2.5 a.i. mg/ml in Assays 2-4, respectively. The percentages of hatched eggs decreased with the increase in conidial concentrations and increased over post-spray days at a given concentration but had no more change from Day 9 onwards. Final egg mortalities reached 65.4, 72.3, 77.7 ]. The effects of both agents and their interactions on the hatch rate of the mite eggs over post-spray days were illustrated by modeling the time-concentration-hatch relationship. The results indicate an alternative to utilize interactions of both agents against spider mites.

Aerial conidia of Beauveria bassiana in an emulsifiable formulation germinated by >95% after 24 h exposure to the regimes of 20, 25 and 30 degrees C with 51%, 74% and 95% RH. Ovicidal activities of the formulation towards two-spotted spider mite, Tetranychus urticae, were assayed at the concentrations of 0, 18, 160 and 693 conidia mm(-2) sprayed separately onto fava bean leaves including 39 (25-76) eggs per capita. All the sprayed eggs on the leaves were directly exposed to the different regimes for hatch after 24 h maintenance in covered Petri dishes. Generally, hatched proportions increased over post-spray days and decreased with the elevated fungal concentrations; no more eggs hatched from day 9 or 10 onwards. Based on the counts of the hatched/non-hatched eggs in the different regimes, the final egg mortalities were 15.0-40.4%, 48.9-66.6% and 62.9-87.5% at the low, medium and high concentrations, respectively, but only 5.6-11.3% in blank controls. The RH effect on the fungal action was significant at 20 and 25 degrees C but not at 30 degrees C whereas the effect of temperature was significant at 51% and 74% RH but not at 95% RH. Probit analysis of the egg mortalities versus the fungal sprays generated median lethal concentrations (LC(50)) of 65-320 conidia mm(-2) at all the regimes, and of only 65-78 conidia mm(-2) at 25-30 degrees C with 74-95% RH. The results highlight ovicidal activities of the emulsifiable formulation against the mite species at the tested regimes and its potential use in spider mite control.