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The effects of test-location, daylength, thrips density, and choice or no-choice test on feeding damage by Frankhiniella occidentalis (Pergande) were studied in chrysanthemum, Dendranthema grandiflora Tzvelev. Under all circumstances, tested cultivars differed significantly in the level of both silver and growth damage caused by thrips feeding on old and young chrysanthemum leaves, respectively. Thrips resistance to both types of feeding damage, measured under the different test circumstances was highly correlated. This means that thrips resistance in chrysanthemum measured in our standardized laboratory experiment gives a good prediction for chrysanthemum breeders who want to select cultivars for thrips resistance under commercial greenhouse conditions. Only test location had an effect on the level of growth damage. In the greenhouse, all chrysanthemum cultivars were more susceptible to growth damage than in the laboratory. The level of silver damage, however, remained constant. Silver damage was only influenced by daylength. All cultivars showed higher levels of silver damage under short daylength compared with long daylength. A density of 10 thlips per plant was found to be high because only 1.6 times more silver damage and 1.1 times more growth damage was found at a 4 times higher thrips density. At the highest density, many thrips died, which resulted in about the same thrips numbers for both treatments at the end of the experiment. Thrips tended to choose among cultivars. However, this did not result in a higher variance in resistance in the free-choice experiment compared with the no-choice experiment.
Document Type: Research Article
Publication date: February 1, 1997
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.