A choice bioassay was used in the laboratory to investigate oviposition preference of the cabbage957g962, Delia radicum (L.), for canola, Brassica campestris L. cv. Tobin, in different developmental stages. Given a choice of two different ages of canola plants, females invariably preferred to oviposit in sand around the oldest plants. Greatest preference was shown for 5-wk-old plants in the stem elongation stage. The effect of oviposition on plants in the five-leaf (3-wk-old), stem elongation (5-wk-old), and initial flowering (7-wk-old) stages was also examined by artificial infestation with 10 eggs per plant and assessment of root damage and numbers of puparia recovered. Root damage or survival from eggs to pupation did not differ significantly with stage of plant development. In a separate experiment, root damage was related (r = 0.76) to introduction of 10,25, or 50 eggs per plant in the stem elongation stage. However, percentage survival from eggs to pupation and pupal weight did not differ significantly among treatments. Microscopic examination of root damage revealed that larvae consumed a narrow band of tissue bordered on the outside of the taproot by a thin layer of periderm and phloem tissue and on the inside by the parenchyma cells of secondary xylem. Independent of larval density, wounds never penetrated to the center of the root. Consequently, no plants in any of the development stages examined were killed by larval feeding. Plants appeared to compensate for damage by a significant increase in root weight with increasing level of infestation.
Document Type: Research Article
Publication date: June 1, 1992
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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.