study on the number of application of diazinon (g10%) insecticide against striped stem borer, chilo suppressalis walker

abstract in order to optimum utilization of diazinon on rice stem borer, chilo suppressalis walker (lepidoptera: pyralidae), an experiment was conducted with two factors including, rice varieties (tarom-mahalli, khazar, nemat) and application times (control with no application, first generation application, second generation application, first and second generations application and four times application). the experiments were based on the completely randomized block design as factorial with 15 treatments and 4 replications. the samplings were conducted before and after the first and second application and at the stages of deadhearts and whiteheads with 5 hills as basis for sampling. the results indicated that year effect was significant on all characters at 1%, but the effects of variety and application times were significant on all characters except yield loss. the effect of year on studied characters showed that the number of infected tillers before and after the first and second applications, deadhearts and whiteheads percentages were the highest in the first year. the variety tarom-mahalli had the highest infection at all sampling times. also, evaluation of the impact of application times on the studied characters indicated that the most infected tillers and whiteheads were observed on the control and second generation application, while the least infection was obtained in the treatments first and second generation application, and four times applications. results showed that even though tarom-mahalli is a sensitive variety to the pest, but one application in first generation could control the pest population and is the safest, and most efficient and economic method for control of c. suppressalis on the such an early and medium maturity variety in paddy fields.