High efficacy of a possible plant elicitor and other phytostimulants against white rust (Puccinia horiana Henn.) in potted chrysanthemum productions.

摘要

Results from experiments conducted in 2008 and 2009 under production situations show significantly fewer symptoms of white rust (Puccinia horiana Henn.) after acibenzolar-s-methyl (ASM, Bion WG50) treatment in potted chrysanthemums (Dendranthema x grandiflorum). Plants were treated 4 times at a 10 day interval and infested plants were placed in the experiment plots 4 days after the first treatments. Rust symptoms were quantified at 4 (2009) and 5 (2008) observation dates. Under high parasitic pressure, plants treated with ASM rarely showed symptoms of chrysanthemum white rust whereas the water treated control received severe damage. Also treatments with 2 natural products (PrevB2, Dipper) resulted in lower symptom development. Laboratory tests revealed low spore germination rates after application of PrevB2 and Dipper but high spore germination with ASM. This finding suggests that ASM has an elicitor effect on chrysanthemum plants against white rust while PrevB2 and Dipper act mainly as a fungicide. A more effective and durable control programme against white rust in chrysanthemum productions is expected when a possible plant elicitor ASM is alternated with directly acting fungicides.