Characteristics of Aphid-Population Growth on Potatoes in Northeastern Maine

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Abstract
The average overall population trend of four species is represented by a sigmoid curve whose peak is reached in this region about August 20. During 15 years the average number of apterous individuals of these four species, counted by the 3-leaf method, has ranged at the peak from 01 to 2,700 per plant. The population is seldom, if ever, limited by factors dependent on density. Rapidity of decline after the peak varies greatly from year to year. Phenomena recognized as population growth characteristics are represented by points or measurable intervals between points on the upward swing of the curve. All these characteristics appear to depend basically upon the tendency of the apterae to move laterally to unpopulated plants early in the summer, and vertically to the less densely populated parts of the plants later. Population growth early in the season is expressed more meaningfully by the percent of plants infested than by the number of aphids per plant, but better by the latter method once all the plants become infested. Although there are limitations to its use, knowledge of these growth characteristics has been beneficial in obtaining adequate aphid control from fewer applications of insecticides and at reduced cost.

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