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A method for evaluating pyrethrum extracts is described. It was found that different strengths of pyrethrum extracts vary directly in the speed with which they paralyze flies. A series of similarly performed tests indicated that the reproducibility of the results is great, especially the values for speed of paralytic action. The per- centage mortalities produced by such a series extended over a wider range but statistical analysis indicated that this variation was well within the limits of errors due to random sampling. Typical paralytic curves are shown and the value of the 50% paralytic point (the time when 50% of the insects are paralyzed) for making comparisons is pointed out. For a series of various concentrations of pyrethrum extracts the differences in mortality were not very great. This criterion of toxicity can only be used for diagnosing differences between extracts which differ widely in concentration. Differences in speed of paralytic action between a 3/4 pound and a 1 pound extract of a fairly powerful grade of pyrethrum powder (0.26% Pyrethrin I) were easily distinguishable and were found to be clearly significant as indicated by statistical analysis. The differences in percentage mortality, analyzed similarly, were not significant.
Document Type: Research Article
Publication date: February 1, 1931
More about this publication?
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.