1Thermal units requirements for development of the american bollworm, Helicoverpa armigera ( HUBNER)

摘要: The present study was carried out under four constant temperatures of 20, 23, 26 and 29oC each ± 1 when the American bollworm, Helicoverpa armigera (Hubner) larvae were fed on the Lettuce vegetable leaves, Lactuca sativa L. The time required for embryogenesis, larval duration and pupal duration as well as pre- and post-oviposition periods decreased as the temperatures increased from 20 to 29oC. The lower threshold of development (to) were12.56, 11.09, 11.23 and 9.99oC for incubation period, larvae, pupae and pre- oviposition period, respectively. The average accumulated thermal units required for development of the different stages was 43.05, 255.66, 231.29 and 9.99 degree-days for incubation period, larvae, pupae and pre-oviposition period; respectively. The lower threshold of development (to) to complete a generation was 10.92oC. The average accumulated thermal units required for a generation was 589.62 degree-days. The thermal units required to complete the development of different stages and completion one generation, as well as helping in the design of development indexes, determining the time required for these stages under fluctuating temperatures in field and forecasting system for establishing and develop the non chemical methods for controlling using the Helicoverpa armigera IPM program.