Abstract

A disease survey conducted in Acacia aulacocarpa, A. crassicarpa, A. mangium and A. auriculiformis trial plots and plantations established between 1985 and 1995 in the states of Kerala, Tamil Nadu, Karnataka and West Bengal, revealed a large number of new and serious diseases. All 4 Acacia spp. suffered more from foliar diseases than diseases of other parts, which included branch/stem cankers, root decay, mildew, blight and dieback. The maximum number of diseases were recorded on A. auriculiformis (28), followed by A. mangium (23) A. crassicarpa (17), and A. aulacocarpa (13). All the diseases recorded on A. aulacocarpa and A. crassicarpa are new records for India. In the case of A. mangium and A. auriculiformis, except for a few diseases already recorded, the rest are new disease records. Although the number of diseases appeared to be high, the number of genera causing diseases. The common fungal pathogen genera found were Colletotrichum, Pestalotiopsis, Alternaria, Curvularia and Phomopsis. Although some of the foliar diseases (such as Phomopsis leaf spot of A. aulacocarpa, and Colletotrichum leaf spot, Cercosporidium leaf spot, an unidentified leaf spot and powdery mildew of A. mangium) were quite severe, resulting in premature defoliation, stem and root diseases recorded in various Acacia species were most damaging as they caused mortality of trees. In A. aulacocarpa and A. crassicarpa, root rot caused by an unknown basidiomycete is responsible for mortality. In A. mangium, root rot caused byGanoderma and dieback by Hendersonula were serious and caused extensive mortality. In A. auriculiformis also, dieback caused by Hendersonula was the most damaging disease