Journal of Agricultural Research (2020), Volume. 7, Issue (2)
Effect of Temperatures on Life Cycle, Longevity and Fecundity of Spider Mites’ Predator, Stethorus punctillum Weise (Coleoptera: Coccinellidae) against Tetranychus truncatus Ehara (Acari: Tetranychidae)
May Thandar Kyaw, Zaw Linn Myo Htun*, Ah Nge Htwe, Aung Zaw Htwe, Thi Tar Oo
In this study, developmental stages, longevity and fecundity of spider mites’ predator, Stethorus punctillum (Coleoptera: Cocinellidae) against Tetranychus trancatus was investigated at different temperature regimes (20, 25, 30 and 35˚C) under laboratory conditions during October 2018 to March 2019. Results indicated that the duration of the egg, larval and pupal stages were significantly affected by temperature. The longest life cycle (19.59 ± 0.31 days) and the shortest (7.66 ± 0.46 days) were observed at 20˚C and 35˚C, respectively. The highest immature mortality percent (63.63%) was observed at 35˚C followed by 36.67% at 30˚C, 20.00 % at 20˚C and 16.67% at 25˚C. The lower development threshold temperature for egg, 1st, 2nd, 3rd, 4th larval instars, pupal and all these stages combined was 11.4, 10.3, 8.0, 8.5, 9.2, 9.4 and 9.49˚C, respectively. Degree day (DD) accumulation was calculated for each developmental stage. Total mean DD estimated for development from egg to adult emergence were 224.28, 226.60, 228.89 and 220.41 at temperatures of 20, 25, 30 and 35˚C, respectively. In this study, 20 - 25˚C was the optimum temperature range for the predator development due to high fecundity, high percent of egg hatchability and low mortality percent.
Keywords: Stethorus punctillum, Tetranychus trancatus, temperature, longevity, fecundity, life cycle.