Occurrence of chrysanthemum downy mildew in Nara prefecture and its control with thermotherapy and fungicide

Abstract

In 2017, chrysanthemum downy mildew, which has not been reported in Japan since 1980, severely affected chrysanthemum production in Nara Prefecture, Japan. We investigated the occurrence of the disease at the fields in Nara Prefecture and the control efficacy of thermotherapy and fungicides against it. In the field survey, over 95 % of plants were diseased in seven cultivars, while no plants with the symptoms were observed in the other six cultivars. This suggests that some chrysanthemum cultivars had resistance to downy mildew. Chrysanthemum cuttings were treated with thermotherapy (treatment with hot water and hot air). The disease prevalence in both treatments was significantly lower than that in the non-treated. Severely diseased plants were sprayed with three fungicides (azoxystrobin, manzeb, and tolfenpyrad). While azoxystrobin and manzeb reduced the disease severity compared with non-treated, its efficacy was not so high. We concluded that the use of resistant cultivars and the application of thermotherapy can effectively control chrysanthemum downy mildew.

An Overview on Fungal Diseases in Angiospermic Plants

“…The fungal infection was decreased by using the thermotherapy means treatment with hot water and hot air and biofungicides as spray on the unhealthy plants. A major difference has been appeared between healthy and infected plants [40]. Ornamental plants are very essential for the whole world which provide the grace to each part of earth, but now the huge reduction has been observed in the production and actual quality of the flowers because of the occurrence of several diseases in the plants by their specific causal organisms.…”