Canola, Brassica napus L., is being evaluated as a winter grain crop in the southeastern United States. The damage potential of insect pests was studied during three growing seasons in the Piedmont and coastal plain regions of Georgia by controlling insects with insecticides at the rosette, beginning bloom, or pod-fill stages of plant development. Canola pod infestations by the cabbage seedpod weevil, Ceutorhynchus assimilis PaykuII, reached 60% at some sites in northern Georgia indicating that this insect will be an important pest of canola in this area. However, C. assimilis was not collected in any year in southern Georgia. Yield responses to insecticide treatments were associated with a complex of aphids, primarily the turnip aphid, Lipaphis erysimi (Kaltenbach), and green peach aphid, Myzus persicae (Sulzer), which caused direct injury to leaves and stems. Aphid injury reduced plant height and winter survival and delayed plant development. Comparison of untreated and season-long treated plots indicated that aphid injury reduced yield by 9.9, 30.4, and 34.8% in 3 yr in the coastal plain region. In northern Georgia, yield losses caused by aphids were ≤2.0% in three of four trials, but aphid injury reduced yield by 32.7% in one trial. Insecticidal control of aphids had the greatest effect on yield during the rosette stage with treatments at first bloom also enhancing yield in some trials. Insecticide treatments at pod-fill stage did not affect canola growth and yield in any trial. Aphids most likely will be a limiting factor in canola production in the southern United States, particularly in the coastal plain region. Aphid management activities should be directed at seedling and rosette stages of plant development.
Document Type: Research Article
Publication date: August 1, 1994
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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.