Effects of different insecticide treatments on the damage by the striped stem borer Chilo suppressalis, controlling efficiency and rice yield
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Key Words：Chilo suppressalis, rice, controlling strategy, chemical control
Abstract：A new trend in the occurrence of the striped stem borer (SSB), Chilo suppressalis, characterized by heavy infestation for all generations, appeared in the recent years. To explore a new insecticidebased controlling strategy for SSB, we designed field plot experiments in early and late rice cropping seasons to investigate the effects of timing and number of insecticide application on SSB damage, controlling efficiency and rice yield. In the experiment region, the first and the second generations of SSB occur in the early season rice field and, the third and the fourth, in the late season rice field. Results showed that spraying 5% Regent SC plus 25% Methomyl at the hatching peak of the 1st and 3rd generations coupled with a 2nd spray 10 d after the 1st spray significantly suppressed SSB larval populations, with controlling efficiency of 92.4% for early season rice and 92.6% for late season rice, respectively. The rates of damaged rice plants and dead panicles were significantly reduced and rice yield increased significantly by 3.98%～4.20% if the plots were sprayed with the insecticides once at the peak of 2nd instar larvae of the 1st and 3rd generation and with additional sprays at the hatching peak of the following generation. Therefore, the new strategy for controlling SSB is spraying for all the 1st to 4th generations.