Abstract
The development and reproductive rate of Japanese and Thailand strains of the diamond-back moth Plutella xylostella were compared at 17, 20, 23, 26 and 29°C. The developmental period of immature stages and longevity of adults of the Thailand strain were similar to those of the Japanese strain. However, the preoviposition period was longer and the fecundity was less in the Thailand strain than those in the Japanese strain at all temperatures. The intrinsic rate of increase of the Thailand strain was always lower than that of the Japanese strain. The developmental threshold temperatures of immature stages and adult maturation were 9.9 and 8.4°C in the Thailand strain, and 9.2 and 8.8°C in the Japanese strain. The thermal constants of immature stages and adult maturation were 294.1 and 86.5 day-degrees in the Thailand strain, and 294.1 and 59.6 day-degrees in the Japanese strain.
