Community based spraying approach needed to control leaf spot disease in arecanut plantations, says former CPCRI Director P. Chowdappa

Leaf spot disease has also been reported in onion, pomegranate, grape since past two years, he says

The leaf spot disease which has hit arecanut plantations, mainly in five districts of the coastal and the Malnad regions, in the State can be effectively controlled by adopting community based spraying approach, according to P. Chowdappa, former Director, Central Plantation Crops Research Institute (CPCRI), Kasaragod, Kerala.

“The severe epidemics of leaf spot caused by fungus Colletotrichum was recorded in arecanut since 2021 even though the disease was reported in 1977 as inflorescence dieback and leaf spot in 1993,” he told The Hindu.

Mr. Chowdappa said that the longer duration of the rainfall this year could be one of the reasons for the disease spreading fast to a vast tracts of arecanut. If not, new variants of the fungus might have also attacked arecanut. Usually the severity of the disease comes down in the summer and it can reappear in the prolonged wet condition if control measures are not taken in the disease hit plantations before the onset of monsoon.

“C. gloeosporloides, has been reported as the causal agent of the leaf blight and inflorescence dieback of arecanut in India. However, seven Colletotrichum species such as C. cordylinicola, C.fructicola, C.gloeosporioides, C.siamense, C.tropicale, C.arecicola and C.karstii have been found to be associated with arecanut leaf spot in Hainan region of China,” he said.

The former Director said that epidemics caused by Colletotrichum species generally occur in rainy, humid, and warm weather, with temperatures ranging between 20°C and 30°C and spread through water splash and wind.

The disease appears as a small round/ellipitical light to dark brown spots surrounded by dark brown margins and yellow halo on leaves, sunken spots with concentric rings on fruits and dieback symptoms on inflorescence.

Through the spray of Bordeaux mixture before the onset of monsoon followed by spray of new generation mixture of fungicides can effectively control the disease. “Community based spraying approach by government agencies using unmanned aerial vehicle should be adopted for effective management,” the scientist said, adding that if the disease is noticed in a particular plantation in an area owners of other plantations in the same area should take up spraying to control its spread.