Abstract: Azoxystrobin inhibited mycelial growth in Colletotrichum capsici, Botrytis cinerea, Rhizoctonia solani and Magnaporthe grisea respectively; it also inhibited conidia germination, conidia production in Colletotrichum capsici, Botrytis cinerea Magnaporthe grisea and sclerotia forming in Rhizoctonia solani. Moreover, it stayed pigment biosynthesis in Colletotrichum capsici and Magnaporthe grisea somehow. SHAM enhanced inhibition by azoxystrobin, especially in those whose mycelia were not sensitive to azoxstrobin, such as Colletotrichum capsici and Botrytis cinerea with the synergistic ratio more than 200. Oxygen consuming test of the mycelia showed that azoxystrobin inhibited all the four fungi’s respiration in the early stages and with the concentration rising up, the effectiveness became better, it was especially significant in Colletotrichum capsici. However, as time went on, the respiration of the mycelia treated with fungicides recovered and even got stronger than the control after 48h, and salicylhydroxamic acid (SHAM) which acted on the alternative oxidase could not inhibit the oxygen consuming. As a result, it seemed that not the startup of the alternative respiration but the other mechanism caused the ineffectiveness.

Key words: azoxstrobin, salicylhydroxamic acid (SHAM), spore germination test, mycelial linear growth test, oxygen consuming test