Influence of environmental factors on the development of the anthracnose diseases of Stylosanthes spp

Abstract

The influence of temperature, period of leaf wetness after inoculation, and relative humidity on the development of the type A and type B diseases of Stylosanthes spp. caused by Colletotrichum gloeosporioides was studied in controlled environment cabinets. Severe disease of both types developed in plants incubated at temperatures of 20-30¦C, and given 24 h of leaf wetness after inoculation. Provided these conditions were imposed, high levels of disease developed following the leaf wetness period, irrespective of the relative humidity (40-50% or >95%). High levels of disease developed for both the type A and type B combinations at temperatures in the range 20-3OoC, but only the type A disease developed at >34¦C. Neither disease developed at constant temperatures of 15 or 37¦C. The use of these results in the development of a model to predict field infection is discussed.