ABSTRACT
The cotton aphid, Aphis gossypii Glover, varies in size and color. During the summer, small yellow forms predominate, while during the spring and fall the aphids are larger and darker. Experiments were conducted to evaluate the growth and reproduction of different aphid morphs in the field and to begin to determine what factors cause the different morphs to be produced. Life history traits of the cotton aphid varied significantly with the color of the aphid. Darker aphids developed more rapidly, weighed more, and produced more progeny. The age of the cotton plant had a small effect on aphid reproduction, but no consistent effect on aphid size or color. Seasonal trends, probably primarily related to changes in temperature, were also apparent. Aphids became darker, larger, and more fecund as temperatures dropped in late August and early September. Survivorship and fecundity usually declined for a short time just before the field was irrigated and then returned to their previous levels. This result suggests that plant water stress may be an important factor in aphid population dynamics, and that irrigation scheduling could be manipulated as an aphid management strategy.
|