Lettuce Yield Reductions Correlated with Methyl Parathion Use
Authors: Johnson, M. W.; Welter, S. C.; Toscano, N. C.; Iwata, Y.; Ting, I. P.
Source: Journal of Economic Entomology, Volume 76, Number 6, December 1983 , pp. 1390-1394(5)
Publisher: Entomological Society of America
Abstract:The effects of methyl parathion and methomyl applications upon yields and photosynthetic rates were examined on lettuce in the growth period between thinning and rosette formation. Reductions in lettuce head weight and density were linearly correlated with the increased numbers of methyl parathion applications made during the season. Applications of methomyl were correlated with increases in lettuce head weight. A positive correlation was found between the percentage of plants that bolted before formation of a marketable head and the number of applications of both insecticides; methyl parathion elicited the greater effect. Both insecticides reduced photosynthetic rates and leaf conductance rates, and reductions were linearly correlated with rates of insecticide applied. The effects of the insecticides on physiological processes were of short duration. Based on calculated reductions in yield, a pesticide threshold of not more than three applications of methyl parathion per season on lettuce in southern California was suggested.
Document Type: Research Article
Publication date: December 1, 1983
- 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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