Abstract: By the methods of determining mycelial growth rate and conidial spore germination, the effects of Bacillus subtilis Tpb55 strain on Alternaria a lternata growth were studied, and the colonization of the strain on tobacco le af was examined under greenhouse and field conditions. It was shown that the ant ifungal substance secreted by strain Tpb55 inhibited the mycelial growth and the conidial spore germination of A. alternata, and damaged the pathogen’s mor phology. The protoplasm of hyphal and conidia cells shrunk, the cells swelled, a nd the cell wall damaged, inducing the leak-out of protoplasm. Within the 0〖KG-*2〗-〖KG-*7〗30 days of inoculation, the colonization rate of strain Tpb5 5 on tobacco leaf was 23×106〖KG-*2〗-〖KG-*7〗189×106 cfu·g-1 fresh mass in greenhouse and 187×106〖KG-*2〗-〖KG-*7〗17933×106 cfu·g-1 fresh mass in field, being maintained a t a high and stable level in the first 3〖KG-*2〗-〖KG-*7〗8 days of inoculation and decreased rapidly thereafter.

Key words: Aulacophora fermoralis chinensis, Aulacophora cattigarensis, Melon crop, Feeding behavior, Cucurbitacin