Ratios for Predicting Field Populationis of Soybean Insects and Spiders from Sweep-net Samples
Authors: Marston, Norman; Davis, Darrell G.; Gebhardt, Maurice
Source: Journal of Economic Entomology, Volume 75, Number 6, December 1982 , pp. 976-981(6)
Publisher: Entomological Society of America
Abstract:Calibration ratios were computed to predict field populations of 40 arthropod groups per m2 from sweep-net samples in soybean. First, absolute populations were estimated by a combination of cage-aerosol and D-Vac techniques. These counts were then related to numbers in 50-sweep samples. The tests were conducted at the beginning of flowering, late pod set, and mid-pod fill in wide-row (76-cm) and narrow-row (38-cm) plantings. A statistical comparison of 11 of these groups demonstrated that the sweep-net collected some groups more effectively than others. Immatures of Hemiptera, Homoptera, and Thysanoptera required especially high ratios to convert to populations per m2 Soybean growth stage also influenced effectiveness of the sweep net for some groups, with a smaller percentage of the total population being collected during pod development than at the beginning of flowering or during pod fill. Row spacing had little effect on the calibration ratios, with one exception; i.e., adults of the soybean thrips, Sericothrips variabilis (Beach), were most effectively sampled in the narrow-row (38- cm) planting.
Procedures are outlined for converting economic thresholds from number per row-m (or m2) to number per 50 sweeps. Relative variation of the sweep data is also discussed, and methods are presented for determining the optimum number of samples for experimental analysis.
Document Type: Research Article
Publication date: December 1982
- 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.
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