Alternarialer alternata is a common and serious tobacco diseases. So far a satisfactory disease-resistant cultivar syst-em has not been established, effective prevention'drugs haven't been developed either.Currently people have been using high residual chemicals to control it,which could pollute the envir-onment and do harm to human body. On the contrary,botanical·pes-ticides are not only safe to humans, animals and environment, but also unlikely make insects and bacteria cause drug-resista-nt. They.can be ...