Interactions between rice plant , Chilo suppressalis (Walk. In response to nitrogen fertilization‎.

The striped stem borer, Chilo suppressalis (Walker), is one of the most important pests of rice in temperate and subtropical Asia. Larval feeding on rice plants at the vegetative stage leads to yellowing and drying of the growing shoot ( deadhearts) while, larval feeding at the reproductive stage results in panicles with unfilled grains (whiteheads). The Interactions among the striped stem borer and rice plants in response to nitrogen fertilization in integrated pest management is very important, partially due to area that nitrogen fertilization is used. A screen house experiment has done in a factorial design with three factor(variety, infestation and fertilization levels) on the basis of completely randomized design to examine the damage and compensation in rice plants when injured by the striped stem borer larvae at tillering stage, as well as larval survival and development of the insect at different nitrogen (N) fertilization levels. Data were analyzed using analysis of variance (ANOVA) by SAS software program. Potted plants were fertilized at late seedling stage at the rates 0, 115, 230, 345 ,460, 575 and 690 mg N/pot, respectively. Three weeks after seedling in pots, plants in 42 pots were artificially infested with newly emerged C. suppressalis larvae, 32 larvae per pot; the remaining 42 plants were not infested and served as controls. The larvae were released near the auricle of tillers using a hairbrush. After infestation, cages were sealed at the top margin by screen to present larvae from escaping. Tillering, height attainment of plants, deadhearts, whiteheads and remaining healthy tillers in each infested plant and healthy tillers in each control plant were counted. Data were analyzed using analysis of variance (ANOVA) by SAS software program. The result indicate that both number of tillers and height in infested and control Plants were significantly affected by the N fertilization level. Tillering was increased in the plants fertilized ( F= 31.44, P=.0001) and Infested plants were significantly smaller than controls at all N levels (F=12.62, P=.0001). Also, The number and percentage of deadhearts (F=3.49, P=0.0106), whiteheads (F=7.78, P=.0001), larval survival (F=6.95, P=.0001) and larval weight (F=3.35, P=.0128) affected by the N fertilization level. The number and percentage of deadhearts , whiteheads, larval survival and larval weight increased gradually as fertilization increased. Conclusively, both the compensation response of rice plants and their suitability for C. suppressalis larvae could be significantly affected by N fertilization levels. Key words: Pest, compensation, White heads, Survival, Dead heart