Effect Of Plant Density On Infestation Of Wheafby Cereal Stem Sawfly (Cephus Pygmaeus L.)

Effect of wheat plant density on rate of cereal sawfly infestation was studied in the experimental field of Seed and Plant Improvement Institute in Karaj during 1996 and 1997 cropping seasons. The experiment was conducted in Randomized Complete Block Design with 4 replication and 5 treatments. The treatments were five seed rates of 130, 150, 170, 190 and 210 kgha-1. The developmental stages of the pest and the host were monitored throughout the experiment. After maturation of larva and in the beginning of diapause stage, the experimental field was harvested. The percentage of infestation was determined for each treatment by counting the number of infested and uninfested stems. The percentage of barren spikes, grain yield and 1000 kernel weight were also determined. The data of two years were analysed according to Duncan's Multiple Range Test. The analysis of variance revealed significant differences among the treatments in infestation by cereal sawfly, grain yield and 1000 kerenal weight, but no significant difference was found in barren spikes, and rate of infestation increased by incerease in plant density. Treatment 130 kgha-1 of seed with 4.13% of infestation was the least infested treatment in companson with the other treatments. However, treatments 190, 170, and 210 kgha-1 with 9.40, 9.25 and 8.71% infestation, respectively, were the most infested treatments. In spite of low percentage of infestation in 130 kgha-1 seed rate, it is not recommended because of low grain yield in the treatment.