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Studies on seasonal phenology and climate change impact on brown planthopper (BPH) with stress proteins and insecticidal efficacy perspective


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Subhash Chander
Division of Entomology ICAR-Indian Agricultural Research Institute New Delhi
Studies on seasonal phenology and climate change impact on brown planthopper (BPH) with stress proteins and insecticidal efficacy perspective

The studies on seasonal phenology and climate change impact were conducted at the Division of Entomology, ICAR-IARI, New Delhi that involved the determination of biochemical constituents in brown planthopper (BPH), Nilaparvata lugens (Stal) from September second week until November second week during 2017 and 2018 with migration perspective. The BPH was observed to appear in the farm from July third week onwards but at this stage it could be collected in very low number. From August first week onwards population shows an increasing trend that continued during September and October, eventually reaching maximum during November first week However, November third week onwards the population declined and finally disappeared. The biochemicals such as protein, water soluble carbohydrates (WSC) and glycogen were observed to be the lowest during September and highest in November. The lower quantity of these biochemicals in September perhaps could be related to with their use for the flight from original habitat to new habitat i,e study area. However, an increase in the concentration of these compounds in October that eventually peaked in November was indicative of likely emigration of the pest to safer areas to tide over low temperature encountered under Delhi environment. Further, the assessment of the effect of elevated CO2 (600±10 ppm) and temperature (40°C) on the expression of heat shock protein genes of BPH revealed that, nlhsp10, nlhsp60, nlhsp70, nlhsp90 were induced after exposure to elevated CO2, elevated temperature as well as to combination of both elevated CO2 and temperature. Among the genes, the expression of nlhsp90 was found to be highest under elevated temperature, while nlhsp70 was observed to be a highly responsive gene to elevated CO2 after one hour of exposure. On the other hand, the combination treatment upregulated nlhsp10 and nlhsp90 after exposure to each of 1, 2 and 3 hours of duration. On the other hand, nlhsp60 and nlhsp70 were upregulated after 1 and 2 hours of exposure but their expression reduced after the 3 hours of exposure. Further, the assessment of the effect of elevated CO2 on the bio-efficacy of buprofezin (0.05%) against BPH at 400, 500, 600 and 700 l/ha spray volumes was also carried out. The peak BPH population did not vary between ambient and elevated CO2 during two years of study. The rice plants grown under elevated CO2 had more vegetative tillers 95 (18%) and reproductive tillers (22.1%) than ambient CO2, that resulted in higher canopy circumference under elevated CO2. However, grain yield (18.8%), seed number per panicle (13.1%) and 1000-seed weight (11.29%) were observed to be lower under elevated CO2 than ambient CO2. Buprofezin (0.05%) proved to be most effective at spray volume of 700 l/ha followed by 600, 500 and 400 l/ha under both ambient and elevated CO2 conditions. However, BPH mortality was observed to be higher under ambient than elevated CO2 at respective spray volumes. Spray volume of 500 l/ha, currently recommended for the management of rice insect pests was found to be not at all effective under elevated CO2, Insufficiency of spray volume of 500 l/ha could be ascribed to increased canopy size under elevated CO2 due to increased tillering. The lower efficacy of buprofezin (0.05%) against BPH under elevated CO2 than ambient CO2 at different spray volume evinced a need for revision in pesticide application recommendations. Key Words: Brown Planthopper, Climate Change, Heat shock proteins, Buprofezin



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