Owing to extreme weather conditions prevailing in the Malnad region for the last one month, the fruit rot disease — a fungal infection locally known as koleroga — has surfaced in the arecanut plantations here.
Premature dropping of affected flowers, nuts, and rotting of arecanut fruits are the main features of this disease, which is caused by the Phytophthora arecae variety of fungus.
Vishwanath M., Deputy Director, Horticulture Department, told The Hindu that arecanut plantations on more than 800 hectares of land in the district have been infected with koleroga.
He said Agumbe, Bidaragodu, Honnetalu, and Nittur gram panchayats have been identified as the worst affected areas.
Copper sulphate mixture, locally known as mailututta, is sprayed four times a year in a gap of 45 days in the Malnad region to the arecanut trees to avoid koleroga. The first spray was undertaken in the first week of June during the onset of the monsoon this year. However, the second spray, which was scheduled for second-third week of July, could not be undertaken as the region received heavy rain during this period. However, rain receded in Tirthahalli and Hosanagar taluks abruptly from July 20 and the temperature soared since then. This sudden variation in weather makes the arecanut trees vulnerable to koleroga. In addition to this, the inflorescence part of the arecanut flower and immature nuts in many trees had partially gone dry in summer owing to moisture stress caused by drought. The affected bunches have become abode for the fungal growth in monsoon.
Duggappa Gowda, a farmer from Agumbe village, said the flowers and tender nuts are falling down from the trees affected with koleroga for the last 10 days. The yield is likely to decline by 40% in the affected plantations this year, he added.
Mr. Vishwanath said farmers have been directed to clear the fallen tender arecanut nuts from the ground to avoid the further spread of the disease. As the rain has receded now, the farmers have been suggested to take up the second phase of spraying to tackle the disease. The department is also providing ₹1,200 as financial assistance for a hectare of land for the farmers to purchase copper sulphate, he added.
