Toxicity of purified fungal toxin hirsutellin A to the citrus rust mite phyllocoptruta oleivora (Ash.)

A toxic protein, hirsutellin A, isolated from culture filtrate during liquid fermentation of the fungal mycelia of Hirsutella thompsonii, was tested using contact/residual and residual leaf bioassay methodologies at concentrations of 0, 10, 32, 56, and 100 &mgr;g/ml against adult citrus rust mite, Phyllocoptruta oleivora. P. oleivora is the natural host of the parasitic fungus, H. thompsonii. Mite mortality increased with an increase in hirsutellin A concentration, reaching virtually 100% at 100 &mgr;g/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. Copyright 1998 Academic Press.