STUDIES ON THE OCCURRENCE AND DAMAGE BY YAM TUBER BEETLES (HETEROLIGUS SPP) IN ANIOCHA AND OSHIMILI AREAS OF DELTA STATE, NIGERIA

摘要

A two-year (2001 and 2002) studies to evaluate the occurrence, population distribution and damage by yam beetles: Heteroligus spp was undertaken in four Local Government Areas in Delta State, Nigeria namely: Oshimili South and North, Aniocha South and North. Beetle population were sampled from farmers fields using light traps in selected locations in the Council areas. Sampling period was April to December for both years. Data collected were number of beetles caught per month, damage indices such as number and size of beetle feeding holes, percentage tuber attacked and tuber yield. Beetle occurrence began in May and were encountered till November. Peak population of beetle occurred in August across the location for the two-year trials. Beetle species comprised of H. meles Billb and H. appiusBurm with the former, the most abundant species regarding the number caught across the locations. Oshimili North and South had higher beetle feeding holes significant at (P < 0.05) than Aniocha South and North for both years and across the locations. No significant difference in size of feeding hole but in terms of percentage tuber attacked, Oshimili South showed higher attack significantly different than Aniocha North both in 2001 and 2002 but not significantly higher than attacked in Oshimili North and Aniocha South in 2001. However, there were no significant difference in the yield of tuber across the locations and for the two-year period. Yam beetle is still a serious insect pest of yam and the two species responsible for tuber damages are H. meles Billb and H. appius Burm in these areas.