Author
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CHARLET, LAURENCE |
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Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings Publication Acceptance Date: 2/29/2000 Publication Date: N/A Citation: N/A Interpretive Summary: The sunflower stem weevil is a pest of cultivated sunflower and crop damage has been reported in Colorado, Kansas, and Nebraska. Larvae overwinter in sunflower stalks, and if populations are high, can cause plant lodging. The objectives were to develop integrated pest management (IPM) strategies to reduce weevil damage. In 1996 and 1997 weevil populations in sunflower fields were studied in both the northern and central Plains and the larval parasite species identified. Between 1997 and 1999 the efficacy of insecticides applied to foliage, in-furrow, and as seed treatments was investigated and sunflower hybrids and accessions were evaluated for resistance. Incidence of weevil infestation and stalk populations were highest in the central compared to the northern Plains. Parasite species numbers were greatest in the central Plains. Foliar and in-furrow insecticidal treatments were effective in reducing densities of weevil larvae, but seed treatment was not. Among the hybrids and accessions evaluated some had about 50% less weevil larvae in the stalks. Effective IPM requires knowledge of the insect's biology, monitoring of fields to determine economic thresholds, the use of resistant cultivars, as well as biological, cultural, and chemical controls. Natural enemies are important in regulating pest numbers. Manipulating the environment to mitigate adverse factors, such as pesticides, can conserve the natural enemies present. Management techniques that reduce weevil densities in the stalks or improve the plant's ability to tolerate weevil attack should be utilized, including the use of resistant hybrids. Chemical control should only be used when adult numbers have reached the economic threshold. Technical Abstract: The sunflower stem weevil is a pest of cultivated sunflower and crop damage has been reported in Colorado, Kansas, and Nebraska. Larvae overwinter in sunflower stalks, and if populations are high, can cause plant lodging. The objectives were to develop integrated pest management (IPM) strategies to reduce weevil damage. In 1996 and 1997 weevil populations in sunflower fields were studied in both the northern and central Plains and the larval parasite species identified. Between 1997 and 1999 the efficacy of insecticides applied to foliage, in-furrow, and as seed treatments was investigated and sunflower hybrids and accessions were evaluated for resistance. Incidence of weevil infestation and stalk populations were highest in the central compared to the northern Plains. Parasite species numbers were greatest in the central Plains. Foliar and in-furrow insecticidal treatments were effective in reducing densities of weevil larvae, but seed treatment was not. Among the hybrids and accessions evaluated some had about 50% less weevil larvae in the stalks. Effective IPM requires knowledge of the insect's biology, monitoring of fields to determine economic thresholds, the use of resistant cultivars, as well as biological, cultural, and chemical controls. Natural enemies are important in regulating pest numbers. Manipulating the environment to mitigate adverse factors, such as pesticides, can conserve the natural enemies present. Management techniques that reduce weevil densities in the stalks or improve the plant's ability to tolerate weevil attack should be utilized, including the use of resistant hybrids. Chemical control should only be used when adult numbers have reached the economic threshold. |
