Yield and Yield Components of Wheat (Triticum Aestivum L.) affected by Aphid feeding and sowing time at Multan, Pakistan

We assessed feeding effect of Schizaphis graminum Rond. and Rhopalosiphum padi L. (Homoptera: Aphididae) on yield losses to wheat (Triticum aestivum L.) (Cv. Sahar) sown on November 05th (early November), November 20th (late November) and December 05th (early December) during 2011, at Multan, Punjab (Pakistan). Aphids were controlled by applying imidacloprid 200 SL with Knapsack sprayer, as one spray (5th March), two sprays (5th and 26th March 2012) and no spray (control). Aphid densities were recorded on weekly basis starting from 12th March. At harvest shoot biomass, number of grains per spike, thousand grain weight and yield were recorded. Polynomial orthogonal contrasts were employed for evaluation of sowing dates, insecticides and their interactions for spray treatments on yield and yield components. Aphid (S. graminum) was dominant over R. padi and its highest number was observed on March 26th, 2012 in all sowing dates of both species. Delayed sowing of wheat increased aphid abundance, however, application of imidacloprid significantly reduced it. Sowing dates and insecticide(s) significantly affected shoot biomass and number of grains/spike. Highly significant differences for thousand grain weight and yield were observed in all sowing dates. Early sowing and application of insecticide(s) significantly increased the yield of wheat. One spray and two sprays of imidacloprid could significantly increase 1000 grain weight and yield in late November and December sown wheat. From this investigation, it is evident that early sowing of wheat is the best for reducing the risk of aphid attack on wheat crop.