Lepidopteran stem borer species abundance and associated damages on irrigated Kilombero low land rice ecosystem in Tanzania

Abstract

Background: Rice stem borers are among the most biotic stresses of economic importance in agriculture. Little was known about stem borer problem in Tanzania prior to this study. Understanding stem borer abundance and damages would help to design appropriate stem borer integrated pest management strategy in rice. This study was aimed at investigating rice stem borerʼs species abundance and their associated damages in irrigated lowland rice ecosystem in Kilombero Tanzania. Materials and Methods: Field survey study on rice stem borer abundance and incidences were conducted in farmerʼs fields on selected rice varieties at varied growth stages in Kilombero district under irrigated rice schemes. Adult moths were trapped by light traps and incidences assessed based on dead hearts and white head in 1 m2 quadrat in field stratum sampled at random. Results: Results indicated the presence of Chilo sp. and Sesamia calamistis in all study areas with Chilo sp., as most abundant species (79.24-92.05%) followed by S. calamist (7.97-20.77%). The abundance of these two stem borer species and their associated damage incidences varied significantly between rice varieties and rice growth stages (p<0.05). The insecticides sprayed on different rice varieties had neither effect on species abundance nor on incidences of stem borers under the study area suggesting that the sprayed insecticides did not control the pest. Conclusion: This study therefore concluded that control measures particularly IPM is highly recommended short of which the control of stem borer will in future be unachievable.