Toxicity of Purified Fungal Toxin Hirsutellin A to the Citrus Rust MitePhyllocoptruta oleivora(Ash.)

A toxic protein, hirsutellin A, isolated from culture filtrate during liquid fermentation of the fungal mycelia ofHirsutella thompsonii,was tested using contact/residual and residual leaf bioassay methodologies at concentrations of 0, 10, 32, 56, and 100 μg/ml against adult citrus rust mite,Phyllocoptruta oleivora. P. oleivorais the natural host of the parasitic fungus,H. thompsonii.Mite mortality increased with an increase in hirsutellin A concentration, reaching virtually 100% at 100 μg/ml using both leaf assay methods. The number of eggs found on leaf disk bioassays within a 3-day period decreased significantly with an increase in hirsutellin A concentration, suggesting that fecundity was affected prior to the death of the host.