Compatibility of the entomopathogenic fungus Beauveria bassiana with the insecticides fipronil, pyriproxyfen and hexaflumuron

The compatibility of beauveria bassiana isolate debi 002 (atashgah) with fipronil, pyriproxyfen and hexaflumuron insecticides was assayed. to determine the impact of the insecticides on the germination of the fungal spore, different concentrations of the compounds were added to the culture medium (malt agar). in order to calculate the mycelial growth in different treatments, each colony diameter was measured and the spores were counted in the surface area to assess its sporulation. the results showed that pyriproxyfen at 1500 ppm and hexaflumuron at 80 ppm completely inhibited mycelial growth, while the inhibitory effect of fipronil at 1600 ppm remained at 76.6%. the inhibitory effect of lower concentrations of all three insecticides was between 10 and 20%. all tested insecticides inhibited the spore production between 80 to 100% at the highest concentrations without any significant differences. pyriproxyfen at 400 ppm and hexaflumuron at all concentrations completely inhibited spore germination, with significant difference, comparing with the rest of treatments. the results indicate that hexaflumuron has the highest inhibitory effect on the spore germination and is not recommended to be used simultaneously with b. bassiana against the insect pests.