Reliability of Pheromone Traps for Cotton Bollworm (Holiothis armigera Hübner) Population Assessment

Abstract

The night activity and relationship between direct counts and trapped Heliothis armigera in cotton field was studied between 10 September and 17 November 1987 in Nakhon Sawan province in the upper Central Plains region of Thailand. For dire4ct counts, six observers using head lanterns were assigned to cover an area of approximately two ha of experimental cotton, capturing bollworm moths with sweep nets. Netting commenced at 19.00 hours and lasted for 30 minutes; it was then undertaken for the same period at 20.30, 22.00 and 23.30 hours. The counts were made every 7 days during the growing period. All female moths were dissected to determine their mating status. Over the same period, 5 pheromone traps were placed in the same field and the trapped moths collected every three days.
The study did not reveal any correlation between the number of trapped moths and the numbers of male, female, virgin and mated females, based on the direct counts. The highest number of captured moths (32.11%) was recorded during the time 19.00 to 19.30 hours; the lowest number (17.49%) was recorded during the period 23.30 to 24.00 hours.