Economic injury level of the cotton aphid, aphis gossypii glover(Hemiptera: Aphididae), on cucumber, cucumis sativus L., in greenhouses

Abstract

Economic injury level of cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) was developed for the cucumbers in greenhouses by conducting following experiments. Experiments were conducted to determine damage of the cucumbers by A. gossypii at vegetative (5- leaf plants) and vegetative-reproductive (10-leaf plants) growth stages. Two different factors, aphid infestation densities and aphid infestation periods, were considered in the experiements. At the vegetative stage, initial infestation densities were 2, 4, 6, 8 individuals/plant and aphids were infested on the third leaf from the bottom of plant. Aphids were maintained for three and five weeks, and excluded by insecticide treatment. At the vegetative-reproductive stage, initial infestation densities were 10, 20, 30, 40 individuals/plant and aphids were infested on the third leaf from the bottom of plant. Aphids were maintained for two, four and five weeks, and excluded by insecticide treatment. Aphid densities were investigated weekly in both experiments. The percent loss of cucumber fruit production (fresh weight) increased with infestation density and infestation period of aphids, which were measured by cumulative aphid-days (CAD). The relationship between percent loss of fresh weight and CAD were Y = -0.0909 X + 1840.2 (r2 = 0.896) and Y = -0.072 X + 1296.1 (r2 = 0.7375) at vegetative and vegetative-reproductive stages, respectively.