Demographic parameters of the cotton aphid, Aphis gossypii (Hom.: Aphididae), population in cotton fields of Gorgan

Abstract

Age-specific life table parameters of Aphis gossypii Glover (Homoptera: Aphididae), one of the major pests of cotton in the Gorgan region, were determined on Gossypium hirsutum L. at different periods during 2002 and 2003 growing seasons. Population projection matrices were used to calculate aphid population elasticity and sensitivities to the changes of aphid survival and fecundity rates. A. gossypii attained its optimum growth and reproduction rates at early season (July). At this condition, the net reproductive rate (17.16 female/female), intrinsic rate of increase (0.349 female/female/time) and finite rate of increase (1.42) were the largest, while population doubling time (1.96 days) was the smallest. At mid and late seasons (August and September) the intrinsic rates of increase were 0.257 and 0.208, respectively. The lowest intrinsic rate of increase (0.073) was observed during a short period in early August. Survival curves of the aphid population were near to Deevy’s type III. The elasticity and sensitivity of nymph survival rates were higher than the adult fecundity rates and decreased relative to the age increasing.

Keywords

• aphis gossypii
• gossypium hirsutum
• demography
• life table
• gorgan