The relation between the incidence of gray-mold, caused by Botrytis cinerea, and climatic conditions was evaluated on 14 clones of Eucalyptus spp. in a nursery localized in Belo Oriente, Minas Gerais, Brazil. All data was based on natural infection. The maximum, minimum and average temperatures, precipitation and relative air humidity were collected from 1991 to 2004. Disease incidence was evaluated monthly in 2004 on eucalyptus mini-cuttings in all phases of the clonal propagation. The presence of the pathogen was checked on water collected from the fertirrigation effluent. The intensity of gray-mold incidence was negatively correlated to the highest temperature. The results indicated that the maximum temperature is the variable that should be monitored for disease prediction. A higher risk of incidence of the disease occurs at temperatures below 27 ºC. Among the 14 clones propagated in 2004, the clone 957 (Eucalyptus urophylla hybrid) showed the lower disease incidence, under natural conditions. It was also found that the fungus is commonly associated to eucalypt mini-cuttings due to the high relative humidity and free water on the host because of the frequent irrigation required for production of mini-cutting. In this case, the development of epidemy is reduced at mild temperatures. Furthermore, reutilized water collected from the fertirrigation effluent may contain pathogen inoculum.
Botrytis cinerea; Eucalyptus; temperature; epidemiology
