Economic Threshold for Cotton Aphid (Hemiptera: Aphididae) on Cotton in the Southwestern United States.
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Cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a common pest of cotton throughout much of the world. In the United States, insecticide applications targeting cotton aphid in cotton are common in the Mid-South, Texas, and California. Cotton aphid population dynamics data were collected from eight insecticide efficacy trials conducted in Lubbock, TX, over a 4-yr period. Among the field populations in the nontreated plots, the instantaneous rate of population growth averaged 0.560.608, and the mean population doubling time was 3.972.16d. For calculating economic injury levels (EIL) and thresholds, control costs were set at US$30.50/ha, market prices were evaluated at US$0.88, US$1.33, US$1.77, and US$2.21kg-lint, and cotton yield potentials were evaluated at 672, 896, and 1,120kg-lint/ha. The EIL we calculated ranged from 66 to 272 aphids per leaf, and averaged 137 aphids per leaf. Economic thresholds (ET) were calculated based on lead times of 1, 3, 5, and 7d before EIL occurs. The mean ET across control cost, market price, and yield potential were 11048, 7031, 4519, and 2913 aphids per leaf at lead times of 1, 3, 5, and 7d, respectively. Most curative pest management tactics in cotton are implemented within 3d of determining need, and the ET at 3d that we calculated (7031 aphids per leaf) overlaps the current recommended action threshold in Texas and California of 50 aphids per leaf.
