Forecasting yield of corn,Zea mays infested with corn leaf aphid,Rhopalosiphum maidis

Abstract: Corn leaf aphid, Rhopalosiphum maidis (Fitch) is one of the most serious corn pests in Egypt. The aim of the present study is to assess the corn yield losses and to build forecasting models of yield related with aphid infestation. Number of aphids/plant were determined during corn growth stages 10 leaves (V10); tasseling (VT); ripening 2 (R2) and ripening 4 (R4). At the end of growing season, yield losses were estimated. Results revealed that infestation with aphids through V10–VT caused 28.14% yield losses at average aphid density 818 aphid/plant. Infestation through R2–R4 caused 16.28% yield losses at average aphid density 1038 aphids/plant. Percentages of yield losses of corn ears through V10–R4 were 14.66, 22.9, 35.28 and 36.03% at average aphid density of 100, 1000, 2000 and 3000 aphids/plant. As ear yield negatively correlated with aphid density, regression analysis was used to construct forecasting yield models. Statistical analysis showed that simple linear and logarithmic models provided a good fit to the data and also indicated that the two models are similar in prediction of ear yield. These constructed models were diagnostic checked using new data. The checking revealed that the linear model is stable and valid where insignificant difference was observed between predicted and actual yield.