evaluation of rice stem borer's damage chilo suppressalis walker (lepidoptera: pyralidae) on different rice varieties

in order to evaluation of rice stem borer's damage (chilo suppressalis walker), on rice ‎cultivars an experiment was carried out by two factors, (three cultivars and five spraying times), in ‎completed randomized block design an factorial sampling was conducted on the hills infested to ‎deadhearts (d.h), whiteheads (w.h) and yield loss. five hills were randomly selected from each plot ‎and evaluated. the effects of variety and spraying times on different variables (except yield ‎variables) were significant (p ? 0.01). the percentage of d.h and w.h at the first year were higher ‎than other years. also, the d.h, w.h and yield loss on tarom-mahali cultivar was higher than others ‎‎(p ? 0.05). the means of percentage d.h and w.h, 1.34, 2.49 were estimated, in the three years, ‎respectively. also, yield loss was estimated 12.20 kg/hec. compare with chek treatment. correlation ‎coefficient between d.h and yield -0.37 and w.h with yield were -0.35 (p ? 0.01). tarom-mahali ‎cultivar was more sensitive to rice stem borer’s damage than khazar and nemat cultivars.‎