Insect pests of rain-fed upland rice and their natural enemies in Ekpoma, Edo State, Nigeria

Abstract

The insect fauna of rain-fed rice, Oryza sativa, was assessed using the sweep net and direct count methods. The objective of the study was to provide basic information on the insect pest complex of rice in the area and their natural enemies. One hundred and five insect species belonging to nine orders and 57 families were found. The insect orders in order of abundance were Diptera (45.67%), Coleoptera (12.77%), Lepidoptera (12.23%), Orthoptera (8.44%), Heteroptera (8.23%), Homoptera (7.03%), Hymenoptera (3.25%), Dermaptera (1.95%) and Dictyoptera (0.43%). Diopsis thoracica Westwood (Diopsidae) (69.43%) was the most abundant dipteran followed by the sarcophagids (14.93%) and calliphorids (7.11%). Members of the family Chrysomelidae represented 50% of the coleopterans followed by the coccinellids (17.46%). While 31% of the lepidopterans were noctuids, 60% were pyralids. The pentatomids (50.57%) were the most abundant heteropterans while the acridids (43%) were the most prevalent orthopterans. The homopterans were mainly Cofana unimaculata Signoret (which represented 79%). The insects were clustered into three groups with D. thoracica alone in group 1, C. unimaculata and Sarcophaga species in group 2 and the rest in group 3. We therefore conclude that D. thoracica is the most important pest of rice in Ekpoma while C. unimaculata may also be very important, but Sarcophaga species appears to be the most important natural enemy in the system.