An experiment was conducted at Department of Entomology, Indian Agricultural Research Institute, New Delhi during 2015–16 and 2016–17 to study the impact of elevated CO2 on functional response of wolf spider, Pardosa pseudoannulata (Boesenberg and Strand, 1906) against brown planthopper, Nilaparvata lugens (Stal, 1854) (Hemiptera: Delphacidae). Spider feeding rate on BPH was higher in jar arena compared to microcosm arena both under ambient CO2 and elevated CO2 conditions. Regression of number of attacked prey (1/Ha) upon prey density per unit area (H) over time duration of experiment (T) in microcosm and in jar arena under ambient and elevated CO2 revealed type II functional response. Attack rate, maximum attack rate and efficiency parameters were higher and handling time was lower in both jar arena and microcosm under elevated CO2 condition compared to ambient CO2 condition. Simultaneously, predators might have consumed more number of preys due to their poor nutrient quality under elevated CO2 compared to ambient CO2. It was revealed that with increase of predator density within the same prey density in same area under both ambient and elevated CO2 conditions, the prey control might have optimized. This information generated would support the planthopper management by regulating predator number for increased predator efficiency.

SUMMARY :Study on effect functional response of wolf spider, Pardosa pseudoannulata (Boesenberg and Strand) in relation to different prey densities of 3 rd and 4 th instar Brown planthopper, Nilaparvata lugens (Stal.) nymphs was undertaken in glass jar arena with '3' spiders under both ambient CO 2 and elevated CO 2 conditions. Under elevated CO 2 condition, predator feeding rate increased from 10.0±3.24 to 31.0±4.36 hoppers/ predator with increase of prey density from 10 to 50 hoppers /predator compared to feeding rate (10.0±3.24 to 33.0±4.39) under ambient CO 2 condition. The feeding rate of the spider under elevated CO 2 was slightly higher than ambient CO 2 condition because elevated CO 2 probably lowered the quality of rice plant and ultimately reduced the quality of prey. In order to compensate for poor nutrient quality of prey, predators might have consumed more number of prey under elevated CO 2 compared to ambient CO 2 . Based on predation study, number of attacked prey (H a ) and prey density per unit area over a period of time (HT) were determined. Regression of 1/H a on 1/HT under ambient CO 2 as well as elevated CO 2 revealed functional type II response of wolf spider on BPH nymph. The attack rate (0.43), maximum attack rate (4.27) and efficiency parameters (0.53) of the predator were higher but handling time was lower (0.71) under elevated CO 2 compared to ambient CO 2 condition. Effect of climate change on functional response of the predator wolf spider, Pardosa pseudoannulata (Boesenberg and Strand) feeding on the brown planthopper, Nilaparvata lugens (Stal.)

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The effect of elevated carbon dioxide (CO2) on protein content, and catalase and peroxidase activity in rice (Oryza sativa L.) plant and brown planthopper (BPH) [Nilaparvata lugens (stal)] was studied in open top chamber (OTC) at elevated CO2 (570±25 μl/l) compared to ambient CO2 (400±25 μl/l). Uninfested rice plants under elevated CO2 had lower protein content but increased activity of both catalase and peroxidase compared to ambient CO2. The BPH infested rice plants had significantly lower protein content (15.89 g/l) and reduced catalase activity (0.78 μmoles of H2O2 decomposed/min/mg of protein) under both elevated and ambient CO2 conditions compared to uninfested rice plant. However, the activity of peroxidase in infested rice plant was non-significantly increased at both elevated and ambient CO2 compared to uninfested rice plants, indicating perhaps that it is an important enzyme in plant defence against BPH in addition to elevated CO2. Further, lower protein content in rice plants under elevated CO2 resulted in lower protein in BPH that fed on them. The activity of catalase and peroxidase in BPH was enhanced when they were fed rice plants under elevated CO2 compared to ambient CO2.