Studies were conducted to examine the spatial distribution of immature Bemisia argentifolii Bellows & Perring and immature Eretmocerus eremicus Rose & Zolnerowich on cantaloupe vines and to develop efficient sampling plans. More B. argentifolii eggs were found on the 3rd leaf from the terminal of a cantaloupe vine than on any other leaf. The density of whitefly nymphs peaked at leaf position 8, whitefly pupae (large 4th instars) peaked at leaf position 11, and immature E. eremicus peaked at leaf position 14. We looked at 4 parameters to describe the distribution of whitefly and parasitoid life-stages among the various leaf positions as follows: (1) median leaf position, (2) the leaf position with the highest percentage of a particular stage, (3) the leaf position where insect counts were best correlated with counts on the entire vine, and (4) the coefficient of variation (CV). All 4 distribution parameters changed throughout the season. In general the leaf positions described by the 4 distribution parameters increased (i.e., were further from the terminal) until the middle of the season when they began to decline. Across the entire season, the 4 distribution parameters for whitefly eggs were associated with leaf positions 3, 4, and 5; for whitefly nymphs with leaf positions 7, 8, and 10; for whitefly pupae with leaf positions 11 and 12; and for immature parasitoids with leaf positions 11, 13, and 14. Based on considerations of cost and precision, it was most efficient to sample leaf 3 for whitefly eggs, leaf 8 for whitefly nymphs, leaf 11 for whitefly pupae, and leaf 14 for immature parasitoids. Using the Taylor power law, density-dependent minimum sample sizes (number of leaves per field) necessary to achieve a predetermined statistical precision (mean ± SE) were estimated. Over a broad range of densities, 50 leaves per field are adequate to achieve a precision of 0.20–0.25 for all life stages. We also provide estimates of the optimum number of leaves to collect per vine based on the within-vine and between-vine variability and the costs (time) associated with counting whiteflies and moving to another vine.
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.