Inhibition of Chlamydospore Germination and Mycelial Growth of Trichoderma spp. by Chemical Fungicides.

For exploring the influences of application and residue of chemical fungicides on chlamydospore preparations of Trichoderma spp., the effects of seven chemical fungicides on chlamydospore germination and mycelia growth of two biocontrol fungi T. harzianum 610 and T. longibrachiatum 758 were studied. Carben-dazim, tebuconazole and difenoconazole showed strong toxicities, thiram and car-boxin showed moderate toxicities, pentachloronitrobenzene and metalaxyl showed weak toxicities to the tested two strains. Mycelia growth of the two strains was more sensitive to most tested fungicides than those of chlamydospore germination. Chlamydospore germination of 610 was more sensitive to tested fungicides than those of 758, and mycelia growth of 758 was more sensitive to most tested fungicides than those of 610. Among the seven fungicides, 98% carbendazim had the strongest effects (EC50 values were 1.64 and 0.05 μg/ml), and 70% pentachloronitrobenzene had the weakest effects (EC50 values were 1.64 and 0.05 pg/ml) for chlamydospore germination and mycelia growth of 610. As for 758, 98% carbendaz-im had the strongest inhibitory effects and 95% metalaxyl had the weakest inhibitory for chlamydospore germination of 758 (EC50 values were 0.62 and 1 108.61 μ/ml respectively), whereas 96.2% tebuconazole showed the strongest inhibitory effects for mycelia growth of 758 (EC50 value was 0.32 μg/ml), and 95% metalaxyl was the weakest (EC50 value was 1 206.29 μg/ml). According to the applied concentration of different fungicides in practice, we concluded that chlamydospore preparations of 610 and 758 could not be combined with carbendazim, tebuconazole, thiram and carboxin for controlling plant diseases, and the pesticide residues to the biocontrol effects should be kept in mind. Chlamydospore preparations of 610 and 758 can be combined with pentachloronitrobenzene and difenoconazole for controlling plant diseases, 758 chlamydospore preparations and germinated chlamydospore of 610 can be combined with metalaxyl for controlling plant diseases, and pesticide residue risk was not serious. [ABSTRACT FROM AUTHOR]