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Impact of Variegated Temperature, CO2 and Relative Humidity on Survival and Development of Beet Armyworm Spodoptera exigua (Hubner) under Controlled Growth Chamber

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Document pages: 14 pages

Abstract: Climate change will have a noteworthy bearing on survival, development, and population dynamics of insect pests. Therefore, we contemplated the survival and development of beet army worm, Spodoptera exigua under different temperatures, (15°C, 25°C, 35°C, and 45°C), CO2 (350, 550, 750 ppm) and relative humidity (55 , 65 , 75 and 85 ) regimes. Maximum larval and pupal weights were recorded in insects reared at 25°C. The growth of S. exigua was faster at 35°C (larval period 7.4 days and pupal period 4.5 days) than at lower temperatures. At 15°C, the larval period was extended for 61.4 days and there was no adult emergence from the pupae till 90 days. The S. exigua hatchling was absent at 45°C. The larval survival ranged from 31.6 - 57.2 , maximum survival was recorded at 25°C, and minimum at 45°C. The maximum (84.27 ) and minimum adult emergence were recorded in insects reared at 25°C and 35°C respectively. Maximum fecundity (384.3 eggs female) and egg viability (51.97 ) were recorded in insects reared at 25°C. Larval and pupal periods increased with an increase in CO2 concentration. The highest pupal weights (128.6 mg larva) were recorded at 550 ppm. The highest larval survival (73.50 ) was recorded at 550 ppm and minimum (37.00 ) at 750 ppm CO2. Fecundity was the highest in insects reared at 550 ppm CO2 (657.4 eggs female), and the lowest at 750 ppm. Maximum larval and pupal weights were recorded in insects reared at 75 relative humidity (RH). The growth rate of S. exigua was faster at 85 RH than at lower RH. The larval survival ranged between 40.0 - 58.5 . Maximum adult emergence (88.91 ) was recorded in insects reared at 75 RH and minimum at 85 RH. Maximum fecundity (447.6 eggs female) and the highest egg viability (72.95 ) were recorded in insects reared at 75 and 65 RH respectively. Elevated temperatures and relative moistness will diminish the life cycle, while hoisted CO2 will drag the life expectancy. Therefore, there is a need for thorough assessment of the impact of climatic factors on the population dynamics of insect pests, crop losses, and sustainability of crop production.

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