Occurrence, mortality factors and within-plant distribution of bollworm, Helicoverpa armigera (Hubn.) on cotton
1994
Solsoloy, A.D. | Domingo, E.O. | Bilgera, B.U. | Solsoloy, T.S. | Bugawan, H.S. | Barluado, Z.D. (Cotton Research and Development Inst., Batac, Ilocos Norte (Philippines))
The seasonal occurrence of cotton bollworm, Helicoverpa armigera, mortality factors and egg and larval distribution on cotton were determined. The peak of occurrence of the pest was recorded at 57, 78, and 106 days after emergence (DAE) on cotton planted within the season, in Guimba, Nueva Ecija, Pozorubio, Pangasinan and Polomolok, South Cotabato, Philippines, respectively. The pest occurred earlier in late-planted cotton than in the early-planted ones, with peaks of occurrence at 54 and 75 DAE, respectively. Rainfall, relative humidity, air temperature and sunshine duration did not significantly influence the population trend of the pest. The mortality factors on the various insect stages were: physiological defects, diseases, natural enemies and dispersion. The eggs were predominantly laid on top of young leaves and growing terminals of the upper third-portion of the cotton plant. The larvae were confined on the upper third-portion from 43 to 64 DAE, at the middle-third portion from 78 to 85 DAE and at the upper third from 92 to 106 DAE. The availability and type of fruiting forms were the primary cues for the pattern in the egg and larval distribution within the cotton plant
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