Toxicity of Fractionated and Degraded Mexican Marigold Floral Extract to Adult Sitophilus zeamais (Coleoptera: Curculionidae)
Authors: WEAVER, DAVID K.; ZETILEH, LARHY J.; WELLS, CAHL D.; BAKER, JAMES E.; BERTSCH, WOLFGANG; THHONE, JAMES E.
Source: Journal of Economic Entomology, Volume 90, Number 6, December 1997 , pp. 1678-1683(6)
Publisher: Entomological Society of America
Abstract:Floral extract of Mexican marigold, Tagetes minuta (L.), was toxic to adult male and female maize weevils, Sitophilus zeamais Motschulsky, under illuminated and dark conditions. The LD50 values ranged from 35 to 47 µg per weevil across sex and photoperiod, whereas LD99 values ranged from 319 to 816 per weevil. Fractionation tended to decrease toxicity. Generally, both sexes were similarly susceptible to a given treatment. Although the original extract and certain fractions probably contained photoactive thiophenes, which are toxic to certain larval Lepidoptera, there was no obvious effect of illumination on toxicity for this beetle species. Air exposure for 24 h, in the presence or absence of light, greatly reduced the toxicity of the unfractionated extract. Chromatographic profiles indicated that fractionation procedures had a significant effect on sample composition and on the amount of nonvolatile matcrial. Air exposure for 24 h had a much more dramatic effect, with concomitant 365-nm UVA or incandescent light causing even greater degradation. Degradation under illumination is the end result of the process that causes photoactivation in susceptible species. Apparently, S. zeamais was not adversely affected by the amount of photoactivation that occurred as the extracts or fractions were degrading under our test conditions. These results are discussed in terms of maximizing the control potential of labile material in subsistence agriculture, particularly when purification is required to remove undesired compounds.
Document Type: Research Article
Publication date: 1997-12-01
- 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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