Thermal requirements and bioclimatic thresholds of sorghum aphid, Melanaphis sacchari (Homoptera: Aphididae) on Sorghum bicolor
摘要
Effect of temperature on the development and survival of the aphid, Melanaphis sacchari was examined under laboratory conditions at seven constant temperatures (15, 18, 20, 25, 27, 30 and 32 °C) on sorghum. The developmental duration for each nymphal instar decreased linearly with increasing temperature from 15 to 30 °C. The oviposition period declined from 13.6 days at 15 °C to 2.5 days at 32 °C. Maximum daily fecundity (4.2 offspring/female) and survival (100%) was observed at 20 °C, while the lowest survival (18.2%) was at 32 °C. The estimated thresholds derived from linear models indicated that Ikemoto-Takai linear model fitted better compared to Campbell model across all the nymphal instars, except for total nymphal developmental rate (R2 = 0.8). Thermal constants required for the development of each nymphal instars and for the total nymph were significantly lower in Ikemoto-Takai linear model (10.9 to 17.6 and 98.9 degree-days, respectively) compared to Campbell model. The Lactin-2, Briere and simplified β type non-linear models accurately described the developmental rates for individual nymphal instars as well as the total nymph. The Lactin-2 model estimated optimal temperatures (Topt) in consistent with the observed maximum developmental rates across all the nymphal instars and total nymphal development. The non-linear thermodynamic SSI model estimated the intrinsic optimum temperatures in the range of 16.6–19.7 °C for different instars and 20.4 °C for total nymphal development of M. sacchari. The temperature dependent growth and development of M. sacchari helps in understanding its field abundance, distribution and implications for pest management in sorghum.