Seed rates and insecticides effects on Russian wheat aphid Diuraphis noxia (Hemiptera: Aphididae) occurrence in irrigated durum wheat (Triticum durum) in the central highland of Ethiopia

The Russian Wheat Aphid (RWA) Diuraphis noxia (Kurdjumov) causes severe damage to wheat in the highlands of Ethiopia. An experiment was conducted to evaluate the effect of seed rates and insecticides on incidence of RWA and grain yield of durum wheat under irrigated filed condition at Debre Zeit Agricultural Research Center, Ethiopia, during 2017. Three insecticides (Dimethoate 40 EC, Actellic 50 EC and Highpro220EW) and one untreated check with six seed rates (75,100,125, 150,175, and 200 kg/ha) were used in split plot design with three replications. Data were collected on plant or plot basis. Data on RWA number was recorded on plant bases. Whereas, leaf rolling, chlorosis, number of deformed head, phenological stages, yield and other yield related parameters were collected on plot basis. Data were subjected to analysis of variance using SAS version 9.3. Mean separation was made using least significant test using Tukey’s HSD (Honestly Significant Difference). The seed rates and insecticides significantly affected the incidence of RWA plant damage (chlorosis), deformed heads, plant height, yield and yield components except the interaction for number of grains per head and thousand seed weight. Dimethoate 40EC and Highpro 220EW sprayed plots gave the highest grain yield and the tallest plant height. The highest grain yield was obtained from 125 kg/ha sown plots and sprayed with Dimethoate 40 EC and the lowest grain yield was obtained from the untreated check sown at the rate of 75 kg/ha. The highest number of RWA per tiller and damaged plants were recorded on the untreated plots and the lowest RWA numbers was recorded, in decreasing order, from Dimethoate 40EC, Highpro 220EW and Actilic 50EC treated plots. Untreated plots with seed rate 150 kg/ha, 175 kg/ha and 200 kg/ha sown plots significantly reduced RWA population than the others. This indicates that there is the possibility of using seed rates above 150 kg/ha to managing RWA. RWA is a serious pest of irrigated wheat in Ethiopia, causing substantial yield losses in different seasons to in irrigated wheat production. The overall results indicated that sowing at a seed rates of 125 kg/ha and spraying Dimethoate 40EC gave the highest yield grain and can be recommended for RWA management under irrigated condition.