Pyricularia grisea and Bipolaris oryzae: a preliminary study on the occurrence of airborne spores in a rice field.

Qualitative and quantitative analysis of fungal air spores in a rice field located around Pavia (North Italy) were made from 10th June to 7th October 1996. Quantitative data were analyzed for the two rice pathogens Pyricularia grisea (Cooke) Sacc. and Bipolaris oryzae Shoem., causal organisms of blast and brown spot. Results showed that B. oryzae was detected at the end of June, reaching its peak in July. Brown spot symptoms in-field were detected six-seven days after the aforementioned peak. Pyricularia grisea was monitored later than Bipolaris as it was detected for the first time on July 21st, reaching its peaks on July 27th and August 6–7th. Field evaluation of the disease showed the presence of blast starting from the first week of July. The knowledge of the atmospheric concentration of Pyricularia and Bipolaris airborne spores together with a correct examination of the crops can yield information about the risk of infection during the vegetative season, thus allowing for a more accurate use of fungicides on rice crops, according to the modern conception of integrated control.