Influence of staggered cultivation and weather parameters on the outbreak of rice yellow stem borer, Scirpophaga incertulas walker in Polonnaruwa district of Sri Lanka

An outbreak of Rice yellow stem borer, Scirpophaga incertulas Walker was occurred in Polonnaruwa district of Sri Lanka during 2018 Yala season causing heavy yield losses. An early pest infestation was also observed in the same area during 2018/19 Maha season. Hence, this survey was conducted to investigate whether there is any relationship among weather factors, cultural practices and rice stem borer outbreak in Polonnaruwa district in 2018 Yala season. Delayed planting, staggered cultivation, lack of awareness among the farmers on identification of the pest and its damage symptoms, along with lack of knowledge on control measures and improper use of insecticides were identified as the major cause of the problem. Continuous cultivation of rice varieties that are more vulnerable to the Rice Yellow Stem Borer attack also contributed to the population build up. The climatic conditions prevailed during the season contributed to aggravate the damage by increasing the RYSB population leading to an outbreak of the pest population resulting in heavy yield losses.