Variation in populations of the introduced pollinating weevil (Elaeidobius kamerunicus) (Coleoptera: Curculionidae) and its impact on fruitset of oil palm (Elaeis guineensis) in India

Abstract

AbstractThe introduced pollinating weevil, Elaeidobius kamerunicus Faust, established itself well in the oil palm plantations in India, but the population fluctuated between seasons reaching its lowest level during the dry season. The wet season was more favourable for the population build-up of E. kamerunicus. As the weevil population in the male inflorescence did not represent the actual numbers present at a given time, an estimation of pollinator force as well as the population size is recommended. Fruitset increased significantly after the introduction of E. kamerunicus, but fluctuated widely between seasons. However, the fluctuation in populations in the male inflorescences, as well as the variation in the number visiting the female inflorescences, did not have any impact on the fruitset. During the dry season when the weevil population was very low, fruitset was high, but during the wet season when the weevil population was very high, the fruitset was lower. Availability of male inflorescences as well as climatic factors such as rainfall, number of rainy days and relative humidity affected the pollinating efficiency of the weevil by reducing the pollen load and its viability. Even though there was a population decline of E. kamerunicus during the dry season there was no reduction in pollinating efficiency and hence there is no need to introduce additional pollinators such as E. subvittatus Faust, which is more efficient during dry seasons.