Crop loss assessment of rice stem borer, Chilo suppressalis Walker on Hashemi rice variety under field conditions

Rice striped stem borer (RSSB) is the most important insect damaging rice crops. The quantification of damages and yield loss caused by this pest is crucial in IPM. In order to determine rice striped stem borer damages on native varieties of Hashemi، experiments were conducted at the Rice Research Institute in 2011. The pest damages could be found in the form of dead hearts and white heads. The relationship between nutrition، damages and rice yield losses were also assessed. This study was carried out in a randomized complete block design with 7 treatments and 3 replications of artificially contaminated rice with eggs masses in cages with dimensions of 2×1×2 m (height × width× length). Treatments were performed at vegetative stage of rice by installing one، three and five egg masses (45-50 numbers) on the leaf blade and in the reproductive stage on leaf sheath with similar density. A control was considered alongside treatments. The results of this study showed that in the vegetative stage of rice plants، five eggs masses treatments caused infection with 9. 44 percent of dead hearts with 3828 kg per hectare and 6. 17 percent yield loss it compared to the control. Also in the reproductive stage، this treatment showed the lowest yield level with 3492. 48 kg per hectare. In the above mentioned treatments، the greatest amount of white heads with 16. 88 percent، and grain yield crop loss by 14. 4 percent was observed as compared to the control. The yield of the control was 4080 kg per hectare. The results showed that for one percentage of dead hearts contamination up to 30 kg and for one percentage of white heads up to 50 kg of yield loss was observed by stem borer infestation.