Observations on the development, survivorship and reproduction of Tetranychus piercei McGregor reared on fresh banana leaves were conducted at 16, 20, 24, 28, 32 and 36°C. The developmental time from egg to adult varied from 7.2 d at 32°C to 33.1 d at 16°C. The developmental threshold temperatures of egg, larva, protonymph, deutonymph, preoviposition and a whole generation were 11.2, 9.8, 11.9, 12.5, 13.3 and 10.7°C, respectively. The effective accumulated temperatures were 72.3, 33.6, 22.2, 27.8, 17.7 and 163.6 day-degrees, respectively. Within the range of 16 to 36°C, the relationships between developmental and survival rates of all immature stages, average number of eggs/female, longevity of adults and temperatures showed parabolic trends. Survival rate was the highest (96.1%) at 32°C; whereas at 36 and 16°C it decreased to 79.1 and 66.4%, respectively. The highest number of eggs (35.8 eggs/female) was recorded at 28°C; and the lowest at 16°C (17.9 eggs/female). Female longevity was the longest (34.5 d) at 20°C and the shortest (8.2 d) at 36°C. The net reproductive rate (R0) was the highest (23.6525) at 28°C and the lowest (5.1044) at 36°C. The intrinsic rate of increase (rm) and finite rate of increase (l) reached maximal values (0.3488 and 1.4174 respectively) at 32°C, whereas minimal values (0.0724 and 1.0752 respectively) were at 16°C. The mean generation time and time for population doubling were the shortest at 36 and 32°C, respectively, which were 7.2192 d and 1.9871 d. The highest population trend index (25.28) was obtained at 28°C and the lowest (4.88) at 36°C. These population parameters and population trend indices increased with temperatures in a parabolic function. The results suggest that T. piercei could develop and reproduce within a wide range of temperatures, and that temperatures from 25.8–32°C are the most suitable conditions for the development, survival and reproduction of the mite.
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Vol. 7 • No. 1