Author
 |
VICK, BRADY |
|
Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings Publication Acceptance Date: 1/30/1998 Publication Date: N/A Citation: N/A Interpretive Summary: The sunflower midge, Contarinia schulzi Gagne, was first discovered in 1971 when it caused severe damage to cultivated sunflower in ND and northwestern MN. Although it is distributed throughout the Great Plains of North America, the sunflower midge has been a serious economic pest only in the northern production areas of ND, MN, and Manitoba. Damage to the sunflower is characterized by distortion of the head (capitulum), result- ing in gnarling or severe cupping. In serious infestations, deformation can be so acute that seedset is prevented. This review describes unpub- lished research from the 1980s about the morphology and feeding patterns of the sunflower midge, attempts to rear the insect in the laboratory, and attempts to characterized the compound responsible for causing head gnarling. Also reviewed are recent papers on the measurement of ethylene evolution by sunflower hybrids and response to 2,4-dichlorophenoxyacetic acid injection as indicators of midge tolerance. Because 2,4-dichlorophen- oxyacetic acid, a synthetic auxin, causes head distortion, a role for endogenous plant auxins in gnarling of the sunflower head is suggested. However, other plant hormones could also be involved. In preliminary experiments, we tested 3 other plant growth regulators, abscisic acid, alpha-naphthaleneacetic acid (another synthetic auxin), and methyl jasmonate for their ability to cause sunflower head distortion. Abscisic acid caused moderate cupping of the sunflower head, whereas alpha- naphthalene-acetic acid caused severe distortion. The results with methyl jasmonate were variable, with a few treatments showing gnarling, while others had no effect. Thus, a role for other plant hormones in midge- induced sunflower head distortion cannot yet be ruled out. Technical Abstract: The sunflower midge, Contarinia schulzi Gagne, was first discovered in 1971 by J.T. Schulz and coworkers (Dept. of Entomology, North Dakota State University) when it caused severe damage to cultivated sunflower in ND and northwestern MN. Although it is distributed throughout the Great Plains of North America, the sunflower midge has been a serious economic pest only in the northern production areas of ND, MN, and Manitoba. Damage to the sunflower is characterized by distortion of the head (capitulum), resulting in gnarling or severe cupping. In serious infestations, deformation can be so acute that seed set is prevented. This review describes unpublished research from the 1980s about the morphology and feeding patterns of the sunflower midge, attempts to rear the insect in the laboratory, and attempts to characterized the compound responsible for causing head gnarling. Also reviewed are recent papers on the measurement of ethylene evolution by sunflower hybrids and response to 2,4-dichlorophe noxyacetic acid injection as indicators of midge tolerance. Other plant growth regulators, such as abscisic acid, alpha-naphthaleneacetic acid, and methyl jasmonate were also tested for their ability to cause sunflower head distortion. Abscisic acid casued moderate cupping of the sunflower head, whereas alpha-naphthaleneacetic acid caused severe distortion. The results with methyl jasmonate were variable, with a few treatments showing gnarling, while others had no effect. |
