Life cycle and control of Colletotrichum nymphaeae, the causal agent of celery stunt anthracnose

Abstract

Colletotrichum nymphaeae, causal agent of celery stunt anthracnose, has caused severe damage to celery production in Nagano Prefecture, Japan. For elucidating the infection cycle, celery seeds in the prefecture were screened on a selective medium and found to harbor C. nymphaeae as did seeds harvested from plants with diseased leaves. When seed samples with 1 and 10 % of the seeds infested were sown and grown, stunt anthracnose developed on seedlings, then finally spread extensively to other plants, suggesting that primary transmission occurred from seeds to seedlings, followed by secondary infection to other plants. These results strongly suggest that the disease cycle of the celery stunt anthracnose is completed through seed transmission in Nagano Prefecture. To disrupt the infection cycle, seed sterilization with hot water was tested. Conidia of C. nymphaeae in suspensions were killed by treatment at 50 °C for 40 min or at >55 °C for 10 min. Seedlings grown from seeds treated at 50 °C for 30 min did not develop any symptoms, and germination was not affected. Thus, hot water treatment at 50 °C for 30 min was the best method to eradicate the stunt anthracnose of celery.