Population Dynamics and Seasonal Abundance of the Beetle Oryctes owariensis Beavois, 1807 (Coleoptera: Scarabaeidae: Dynastinae) in Raphia Palms in Bayelsa State, Nigeria

Abstract

Oryctes owariensis (Coleoptera: Scarabaeidae) beetle is a destructive insect pest of both raphia and oil palms, causing damage to the fronds and trunk thus leading to low yields and subsequent death of infested palms. This study was aimed at monitoring the seasonal abundance of the beetle using visual lure or light traps suspended on poles around raphia palm farms designed as experimental sites (Locations A, B, C and D) for a duration of two years (2018 and 2019) in Bayelsa State. Four sampling seasons were engaged in the study: Four months of dry (January- April) and four months of wet (June- September) yearly. The lamps were powered seven consecutive nights monthly. Beetles trapped were counted daily and the numbers recorded. The result showed that the beetle had one generation per year, was nocturnal with seasonal activity spreading out from dusk to dawn. Adult population was highest within the dry sampling months of March to April as the insects mate for breeding, the wet months June and July recorded drastic fall in the number of trapped beetles while August and September recorded no catch. A total of 283 beetles were captured during the dry season against 8 trapped at the wet. Therefore, the high efficiency of the light traps as capture/ monitor tools in ascertaining the seasonal abundance of Oryctes owariensis beetle in raphia palm farms is a possibility for use in Integrated Pest Management Programs for controlling the pest population before they reach the economic threshold level.