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Dietary nutrients were identified by mass spectroscopy from chromatographic isolates of the neutral lipid fraction of Bermuda grass, Cynodon dactylon L. (Pers.). These included methyl and ethyl linolenate, vitamin E (y-tocopherol, ∝-tocopherol), and the 3 sterols: campestrol, stigmasterol, and sitosterol. Gas liquid capillary chromatographic analyses of these molecules indicated significant differences among the Bermuda grass genotypes, especially in sterol composition. Campestrol was present in most of the genotypes examined with stigmasterol and sitosterol, showing the greatest variability in abundance and occurrence among the Bermuda grass lines. Larvae of fall armyworm, Spodoptera frugiperda (J. E. Smith), fed on diet supplemented with the lipid fraction showed significantly higher larval weight accumulation (28-54%) compared with controls. Larval growth was variably dependent on the genotype or somaclone lipid profile. These findings confirm a major role for neutral lipids in insect growth physiology and, by implication, are key elements in Bermuda grass nutritive value. Additionally, an antifeedant also was isolated from Bermuda grass. A crude sohxlet extract from Bermuda grass (line OSU 71 X6-7) was sequentially fractionated by silica gel flash column and reverse-phase high-pressure liquid chromatography (HPLC). A bioassay-guided scheme with the fall armyworm yielded an active antifeedant fraction eluting at 10% EtOAc/ CH2Cl2, from which a single active component was isolated by HPLC. The biological effects of these isolates on neonate fall armyworm larvae included a retardation of larval growth (80% reduction in larval weight) and an increase in duration to pupal metamorphosis (70%) that were significantly different from either control treatments or other chromatographic fractions. A concentration-dependent antifeedant response with the isolate to topically treated diet plugs was observed.
Document Type: Research Article
Publication date: October 1, 1997
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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.