الفهرس 
MAIZE, Zea mays L. YIELD LOSSES DUE TO INSECT PEST INFESTATIONOnly 14 pages are availabe for public view
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Abstract
This study aimed to assess the yield losses of the maize due to stem borers; Sesamia critica, Ostrinia nubilalis and ear rot disease, Fusarium moniliforme under field conditions in three varieties of maize (white, yellow and sugary corn). The yield losses were assessed by compare the actual yield for the absent or infected plants with the expected yield for the intact plants. Also, the effect of insecticide treatment on yield losses was investigated using Jasper 3.4 %ME (Emamectin) in a recommended concentrations (120 ml/ feddan). The yield losses was conducted using the conventional and analytical methods to compare whichever more accurate.
In order to predication of yield losses caused by stem borers infestation, the regression between maize yield losses and the percent of infestation with corn borers, S. cretica and O. nubilalis was evaluated.
-In this study the yield losses due to the tested pests for three maize varieties under insecticide treatment were also estimated at different sawing dates in four small holder corn fields in El-Behiera governerate, then we assessed the compensatory yield for the yield losses whether due to the absence or infestation of plants.
1. Estimation of grain yield losses per corn plant of three corn varieties affected by infestation with three pests and treatment with insecticide under field conditions.
To assess the yield losses of corn plants due to the pest infestation, the effect of insecticide treatment, corn varieties and the pest infestation on grain weight/ear of corn were measured. The analyzed results of the present study shows that the grain weight/ear of intact maize were significantly influenced by the corn Varity, while, it wasn’t affected by insecticide treatment. The highest grain weight was obtained in white corn (154.33 gm/ear), followed by yellow corn and the sugary corn recorded the lowest grain weight (36 gm/ear). . It was clear that the insecticide treatment caused an increase of grain weight by 3.44 gm/ear. Regardless the insecticide treatment, the means of grain weight/ ear were significantly difference, where, the means of grain weight for white, yellow and sugary corn were 145, 108.17 and 37gm/ear, respectively.
Under the sugar-cane borer, S. creticae infestation, the means of grain weight / ear as affected by insecticide treatment of maize varieties were measured. Regardless the corn varieties, the difference between grain weight of treated and untreated plants reached 9.34 gm. The grain weight /ear of corn varieties were descending from white grain maize (66.5 gm./ear) to yellow grain maize (38.5 gm./ear) to sugary maize (19 gm./ear). It was found that the heaviest grains/ear recorded by white grain maize under insecticide treatment (50 gm./ear), while, the lightest grain weight (18 gm./ear) was recorded by untreated sugary maize. Generally, the grains weight was clearly decreased under S. creticae infestation, when compared with the grains weight in intact plants.