Correlation of disease with meteorological factors and management of Septoria leaf spot of chrysanthemum (Chrysanthemum grandiflorum)

Abstract

Leaf spot severity was high at 25°C and lowest at 35°C temperatures. Relative humidity more than 96% influenced the spread of the disease to maximum by causing 57.20% disease severity. In field, the disease usually appears in June and reached to maximum in August with rise in relative humidity and rainfall in both the years (2003–04). The simple, partial and multiple correlations, indicated a positive correlation of disease concerning rainfall and relative humidity while temperature had a negative effect on disease development. The co-efficient of multiple determinations signifies 66.03 and 67.40% variation with the positive weather factors of disease development. In in vitro studies, 7 fungicides three from each systemic (contaf, roverol and bavistin) and non-systemic (SAAF, dithane M45 and dithane Z78) category arrested the mycelial growth of the pathogen up to 73% generally at higher concentrations. In field contaf, SAAF, roverol were found equally good in controlling the disease, followed by dithane M45, dithane Z78 and benomyl.