Epidemiological studies of Colletotrichum gloeosporioides disease of cocoa

Abstract

SummaryThe intensities of foliar infection (leaf blight and shot hole) and pod rot, caused by Colletotrichum gloeosporioides, were recorded from a cocoa‐areca mixed garden and a cocoa‐monocrop garden during 2 years. The intensity of pod rot was recorded from both the gardens. The intensities of leaf blight and shot hole gradually increased from July, reached a peak during September‐November, decreased thereafter and reached the lowest level during April‐June. Increase in leaf infection was associated in both plantings and in both years with the period of rain (June‐November). The phylloplane population of C. gloeosporioides also increased during June‐November when the temperature tended to be low and constant with high rainfall and relative humidity. During this period there were few susceptible stages of pods (cherelles and young pods) and pod infection was very low. Nearly mature pods were free from infection. I n both years, pod infection was more in the cocoaareca mixed garden than' in the cocoa‐monocrop; it was observed during January‐May, when the susceptible stages were mostly prevalent but when the C. gloeosporioides population was low and the climatic factors appeared to be relatively unfavourable. This may be one reason for the lesser incidence of pod rot when compared to foliar disease.