Kan suksa thang niwetwitthaya khong non yai phak, Plutella xylostella L. (Lepidoptera: Plutellidae) lae sattru thammachat nai prathet Thai.

The female produced an average of 233.5 eggs and the incubation period was 1.87 += 0.34 days. The larva had four instars and mean duration of each instar was 2.42, 1.86 and 3.63 days, respectively. The growth increment in terms of the width of the head capsule assumed a geometric progression with a ratio of 1.5022. The prepupal and pupal stages were 1.11 + 3.20 days, respectively. Adult male life span was 16.17 days, while that of the female was 9.50 days. Preoviposition period of the adult female was 0.1 day and the highest number of eggs were counted in the second day of the oviposition period as fifty-seven eggs. Total life-cycle from egg to adult emergence averaged 15.52 days. Life table analysis yielded the following population parameters: the net reproductive rate (Ro)=24.5539, the cohort generation time (Tc)=16.3244, the capacity for increase (rc)=0.1961 and the finite rate of increase (lambda)=1,2166, the percentage of mortality was high in the egg stage (84.25 percent) followed by pupal, first instar larval, prepupal and second instar larval stage. The spatial pattern of distribution of P. xylostella larvae were contageous during transplant to harvest stage of the green-chinese cabbage (Brassica juncea). Three sampling methods were employed to count the larva and pupa at age plant of 5, 6, 7, 8 and 9 weeks. Stratified random sampling which used a sample of 10, 15, 10, 1 and 3 percent, respectively was the most suitable. The population osillation of the larva and pupa were not related with temperature, relative humidity, rainfall, wind velocity and sunshine duration. The natural enemies found on the larval stage and pupal stage were Apanteles sp. and chelonus sp., respectively. A high cost parasite relationship was indicated (r=0.8847). On using the sticky pheromone trap, the number of adult males were highly related with counted larva from the field in the same week (r=0.720) and the flight activity period of adult males was about 18.00-21.00 and 03.00-06.00 hr.