Effect of oil suspended conidia of Metarhizium anisopliae var. major on mortality of the sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae)

Abstract

Wheat is a crop with important economic and political values. The sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae) is the most important pest of wheat and barley in over 15 million hectares of west and central Asia. The management of this pest is considered to be difficult for wheat producers. One of the potential control strategies is to use entomopathogenic fungi such as Metarhizium anisopliae to control the insects. The aim of the current study was to determine the effect of different composition of oil on the pathogenicity of M. anisopliae var. major. This research compares the efficacy of three isolates of M. anisopliae var. major, with three kinds of oils to control migratory summer generation of the sunn pest, E. integriceps under laboratory conditions. The results demonstrated that the rate of mortality (after 10 days) was 75%, 88% and 90% with 10⁸ spores/ml of isolates suspended in ADDIT®, EC®, Citoweet® oils, respectively, at 75% relative humidity. However, the rate of mortality was 38% when the conidia were suspended in Tween-80® at the same conditions for the most effective isolate (M₁₄). The Citoweet® scored the highest enhancement in the efficiency of M. anisopliae var. major (for all three isolates) against summer population of the sunn pest. Oil formulation increased fungal virulence on E. integriceps and enhanced fungal virulence towards insect. Since insect cuticle especially epicuticle (lipid layer) is the primary site for the establishment of mycosis, oil formulation increase the adhesion of spore to the insect cuticle through hydrophobic interaction between the spore and cuticle surface. We propose developing the results in natural conditions of field.

Keywords:

• Eurygaster integriceps
• Metarhizium anisopliae var. major
• mortality
• oil formulation

Acknowledgements

We thank the Biological Control Department of Iranian Research Institute of Plant Protection, Tehran, Iran, and the Entomology Section of the Department of Plant Protection of Shahed University, Tehran, Iran.