Detection and management practices of black shank disease caused by Phytophthora nicotianae in tobacco crops

Abstract

Tobacco (Nicotiana tabacum L.) is one of the most important economic factors in Cuba. The second disease of importance is the black shank caused by Phytophthora nicotianae Breda de Hann. From 1985-1986 it’s incidence increased, although Metyl Bromide and Metalaxyl were used, the method control was deficient, that’s why several studies were carried out, one of there was the search for a detection and quantification method of soil pathogens, and other control alter- natives such as, area selection, crops rotation and the use of the Trichoderma biocontrol in soils. For the quantification of the pathogen in soils it was proved that the modification of the selective medium described by Kannwischer y Mitchell (1978) was efficient to determine the contamina- tion level of the soils in the fields, thus they were high in the plantations (3-39,5 propagules/g of soil ) and not in the fields used as seedbeds in which the pathogen was not detected in soils.This method allows us to select those fields for crops in which the pathogen was not detected in soils. This method allows us to select those fields for crops in which the pathogen is not detected in soil, or in which the contamination level is too low, thus avoiding the development of epidemics. Besides it was tested that the high density of sowing favored the development of the disease, and that area selection and crop rotation for 3 years, also the use of Trichoderma biocontrol were effective to diminish the damage of black shank in this crop.