EFFECTS OF SELECTED PESTICIDES ON THE GROWTH OF FUNGI FROM HIRSUTELLA GENUS ISOLATED FROM PHYTOPHAGOUS MITES Cezary Tkaczuk, Ryszard Miętkiewski University of Podlasie, Department of Plant Protection Prusa 14, 08-110 Siedlce, Poland e-mail: tkaczuk@ap.siedlce.pl Accepted: August 18, 2005 Abstract: The aim of this study was to determine in vitro effects of selected pesti- cides on the growth of fungi: Hirsutella nodulosa, H. brownorum, H. kirchneri and H. necatrix, isolated from phytophagous mites. Insecticides and herbicide were added to the medium at the following rates: 0.1; 1 and 10 times the field rate recom- mended by manufacturer. Fungicides were applied at the following rates: 0.01, 0.1 and 1 times the rate recommended by manufacturer. Pesticides tested in this exper- iment showed a strong inhibiting effects on the growth of fungi from Hirsutella ge- nus – natural pathogens of phytophagous mites. Among all pesticides tested, fungicides showed the strongest inhibiting effect on the growth of Hirsutella species and especially flusilazole (Punch 400 EC). Amitraz (Mitac 20 EC) and phosalone (Zolone 350 EC) were the most toxic among tested insecticides. Fungi H. necatrix and H. kirchneri isolated from eriophyid mite Abacarus hystrix were the most resis- tant to toxic effect of tested pesticides but H. nodulosa isolated from Tarsonemidae mite seems to be the most susceptible. Key words: pesticides, Hirsutella fungi, toxicity INTRODUCTION Our knowledge of fungal diseases of mites is still fragmentary, although an in- creasing number of reports on this subject have been published in recent years (Chandler et al. 2000; McCoy 1996; Miętkiewski et al. 2000; Miętkiewski et al. 2003; van der Geest 2004; van der Geest et al. 2000). The most frequently encountered fun- gal pathogens of mites belong to the genera Neozygites of the order Entomophthorales and Hirsutella of the order Hyphomycetales. Fungi from Hirsutella genus are very impor- tant factor in reduction of phytophagous mite population causing up to 60% of mortality (Miętkiewski et al. 2000; Miętkiewski et al. 2003). They are used in bio- logical control, e.g. acaricide “Mycar” based on H. thompsonii (McCoy 1996). Vol. 45, No. 3 (2005) JOURNAL OF PLANT PROTECTION RESEARCH