The number of plants that sampling requires in aphid population studies often exceeds one hundred. Thus, only quick and nondestructive methods can be used to sample this pest in a reasonable time interval. We propose a visual method for estimating the density of the aphid Macrosiphum euphorbiae (Thomas) on tomato plants reared in greenhouses. After approximately 1 min of visual observation plants can be assigned to abundance classes, the boundaries of which are roughly the powers of √10. Precise counts were collected simultaneously on sets of reference plants from the same greenhouse. Projection pursuit nonparametric regression was then used to provide unbiased estimates of aphid densities from the abundance classes and several easily gathered explanatory variables. The robustness of the method was evaluated by testing the models on the complementary data sets from plants in which the aphid densities were precisely counted. In both single and twin-row cultural conditions, for the reference and complementary data sets, the order of magnitude of the error was less than one class rank per plant. The investigation time was reduced by approximately 10-fold compared with the exact counting method. This easy-to-teach field method could be useful in large-scale population surveys and for optimizing integrated pest management strategies.
Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.