Impact of Variegated Temperature, CO&SUB&2&/SUB& and Relative Humidity on Survival and Development of Beet Armyworm &i&Spodoptera exigua&/i& (Hubner) under Controlled Growth Chamber

摘要

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), CO_(2) (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 CO_(2) 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 CO_(2). Fecundity was the highest in insects reared at 550 ppm CO_(2) (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 CO_(2) 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.