Infestation and Yield Losses Due to Sesame Webworm (Antigastra catalaunalis, (Duponchel) on Different Sesame Varieties in Western Tigray, Northern Ethiopia

Sesame (Sesamum indicum L.) is the most important oilseed crop in Ethiopia. It is basically grown during the summer season in different regions of the country and produced mainly in the northern and northwestern lowlands of Ethiopia. The production of sesame is low because of insect pests such as sesame webworm, sesame seed bug and gall midge. Among these pests, sesame webworm is one of the most important insect pests and it attacks the crop at all growth stages and causes a significant yield loss. Therefore, the present study was aimed to assess the infestation and avoidable yield losses of sesame due to sesame webworm on different released sesame varieties at field conditions. A field experiment was conducted to assess the infestation and yield losses with respective cost-benefit of nine released sesame varieties to sesame webworm in paired plots (treated with Diazinon 60% EC and untreated) in RCBD with three replications in 2016 production year. There was a significant difference (p<0.001) between the protected and unprotected plots of each variety in leaf, flower and capsule injury. Protection of sesame from the webworm with insecticide effectively reduced leaf (0.02%), flower (<2%) and pod (<1%) damage to very low levels, On the other hand, the unprotected sesame had high levels of infestation. The highest capsule injury was recorded on BaHa-Necho (9.68%) and varieties Adi, Setit-2 and Borkena sustained <5% capsule injury. Grain yield was also increased significantly (p<0.001) in the protected plots of the nine varieties as compared to their corresponding unprotected plots. Maximum yield was obtained from Setit-2, Setit-1, Humera-1 and Higher in both treated and untreated plots. The highest avoidable yield losses were obtained from Adi, Gonder-1, BaHa-Necho, and BaHa-Zeyit with respective cost-benefit ratio 2.27, 2.02, 2.12 and 2.03. Therefore integration of sowing the varieties Setit-2, Setit-1, Humera-1 and Hirhir and spraying with Diazinon 60 EC, at a rate of one liter per hectare at 2, 4 and 6 weeks after crop emergence (WAE) has potential to reduce the yield losses of sesame due to sesame webworm infestation and to increase yield of sesame.