BioControl (2011) 56, 893-902

Guoxiong Peng and Yuxian Xia (2011)
The mechanism of the mycoinsecticide diluent on the efficacy of the oil formulation of insecticidal fungus
BioControl 56 (6), 893-902
Abstract: Adverse conditions, including low humidity, UV irradiation, and high temperature, appreciably affect the efficacy of mycoinsecticides. Oil formulation increased the virulence of Metarhizium anisopliae var. acridum (Ascomycota: Hypocreales) against locusts and grasshoppers by reducing the dependence on saturated water. A mycoinsecticide diluent (a water-in-oil emulsion) has been widely used to dilute the oil formulation of M. anisopliae in China. The aim of our study was to elucidate the mechanism by which the mycoinsecticide diluent improves the virulence of M. anisopliae. We investigated the effects of the mycoinsecticide diluent on the virulence, invasion speed, and viability of the conidia under various adverse conditions. The results demonstrated that the mycoinsecticide diluent significantly improved the virulence of conidia at low humidity (68, 75, and 84%). In particular, at an RH of 68%, the LT₅₀ for locusts treated with the emulsion was 5.4 days and was 31.6% lower than the value for locusts treated with an oil formulation. In addition, the concentration of the hyphal bodies found in the haemolymph of locusts treated with emulsion was about 27-fold higher than that in locusts treated with oil formulation four days after inoculation. This result was further confirmed by determining the concentration of M. anisopliae var. acridum DNA in locust haemolymph using quantitative PCR. The percentage germination of conidia in the emulsion was also significantly higher than that in oil at 68% RH. There was no significant difference in percentage germination between conidia treated with the emulsion and oil when exposed to irradiation with ultraviolet-B (UV-B) or high temperature. These results demonstrate that the mycoinsecticide diluent enhances the virulence of M. anisopliae formulated in oil at low humidity by providing adequate water for germination without interfering with the UV tolerance and thermotolerance of the conidia.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Yuxian Xia

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
formulation/storage of bioagents
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Locusta migratoria
Metarhizium acridum (entomopathogen)	Locusta migratoria