Effect of cultural practices on the occurrence of pod and stem blight and purple blotch, and on soybean growth

Effect of cultural practices on the occurrence of pod and stem blight and purple blotch, and on soybean growth

2001

A:PS

Deterioration of pod and seed quality by pod and stem blight and purple blotch is a serious problem in the pro-duction of vegetable soybean. Major inoculum sources for the causal pathogens, Phomopsis spp. and Cer-cospora kikuchii, are soybean straw and debris. Phomopsis spp. have been known to be either limited for hyphal growth or latent in immature soybean tissues. In this experiment, cultural practices using these ecological traits of the pathogens were applied as a control measure. In plastic mulching, seed infection was remarkably reduced by drip irrigation as compared to overhead sprinkling, but not reduced in no mulching cultivation. Control value of plastic mulching was 28.0% for pod and stem blight and 29.3% for purple blotch, which was lower than that of benomyl application. By the first week in June, 78% of overwintered soybean straw examined contained matured alpha spores in pycnidia, acting as primary inoculum. Secondary inoculum of Phomopsis spp. was observed abundantly throughout from mid June to September on fallen cotyledons from current crops and subsequently was found on petiole debris. Consequently, both plastic mulching and drip irrigation were effective to some extent for controlling pod and stem blight and purple blotch without significant reduction in soybean yield, and the cultural practices in combination with field sanitation resulted in removing more the secondary inoculum.

v.7(2):107-111, RESEARCH IN PLANT DISEASE

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