Author
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Charlet, Laurence |
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Submitted to: Biological Control News Midwest
Publication Type: Other Publication Acceptance Date: 6/8/1995 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Sunflower has become an important U.S. oilseed crop. It is one of only a few native to North America. Insects have evolved with the plant and many have moved to the cultivated crop. Although hundreds of insects have been recorded from sunflower, only a small number have achieved pest status. Natural enemies have been a significant factor in preventing many insects from becoming economic pests. An important pest of sunflower has been the sunflower stem weevil. Larvae of this weevil damage the crop by feeding, developing, and overwintering in the stem. This weakens the stem and can result in lodging of the plant prior to harvest. Parasitoids attack both the egg and larval stages of the weevil. The braconid wasp, Nealiolus curculionis is the most abundant larval parasitoid attacking the weevil. The immature parasitoids overwinter within diapausing weevil larvae in the sunflower stalk. Field densities of adult parasitoids have been quite variable, but the consistent rates of parasitism suggest that N. curculionis effectively locates hosts under varying host population densities. Delayed planting has been an effective cultural control tactic for reducing larval numbers in sunflower stalks. The parasitoid effectively attacks larvae of the sunflower stem weevil in sunflower plants from different planting dates. Since the parasitoid appears to be a consistent mortality factor in the population dynamics of the sunflower stem weevil, it is important to utilize cropping practices that also conserve and protect these natural enemies. |
