|Kirk, William -|
|Sprague, Christy -|
Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 22, 2012
Publication Date: January 1, 2013
Citation: Kirk, W.W., Hanson, L.E., Sprague, C.L. 2013. Glyphosate and fungicide effects on Cercospora leaf spot in four glyphosate-resistant sugar beet (Beta vulgaris) varieties. Crop Protection. 44:38-43. Interpretive Summary: The herbicide, glyphosate, has been shown to reduce severity of some foliar diseases on soybean and wheat. Cercospora leaf spot, caused by the fungus Cercospora beticola, is one of the most important foliar diseases problems in Michigan sugar beet production. The recent introduction of herbicide-tolerant sugar beet allows for testing of glyphosate, alone and in combination with standard fungicides, for the management of Cercospora leaf spot. Four glyphosate tolerant commercial sugar beet varieties were inoculated with C. beticola to promote development of Cercospora leaf spot. Plants were treated with four different herbicide treatments: 1) no herbicide (hand-weeded control), 2) a standard herbicide program in use in the industry (combination of 4 herbicides), 3) three applications of glyphosate, and 4) four application s of glyphosate. Herbicide treatments were evaluated alone and in combination with a Cercospora leaf spot fungicide control treatment standard in the growing region. Plant variety and the fungicide treatment had signficant effects on Cercospora leaf spot severity. However the herbicide treatments had no signficant effect on disease severity. Results from this research indicate that glyphosate, alone or in combination with the fungicides tested, did not signficantly contribute to disease control for Cercospora leaf spot in sugar beet.
Technical Abstract: Glyphosate has been shown to reduce foliar diseases in soybean and wheat. In fact, currently there is a patent application for a synergistic combination of glyphosate and a fungicide for disease management. Cercospora leaf spot (Cercospora beticola) is one of the most significant foliar disease problems in Michigan sugar beet production. The recent commercialization of glyphosate-resistant sugar beet allows for the testing of glyphosate and glyphosate-fungicide combinations for the management of Cercospora leaf spot. To allow for controlled testing, the glyphosate-resistant sugar beet varieties, ACH 827RR, Hilleshög 9027, Hilleshög 9028, and Hilleshög 9029 were inoculated with Cercospora beticola for the development of Cercospora leaf spot. Four different herbicide treatments: 1) no herbicide (hand-weeded control), 2) a standard-split herbicide program (two applications of desmedipham & phenmedipham + triflusulfuron + clopyralid + non-ionic surfactant), 3) three applications of glyphosate, and 4) four applications of glyphosate were evaluated alone and in combination with a standard Cercospora fungicide program. Variety and fungicide main effects were significant for Cercospora leaf spot severity. However, regardless of the herbicide program Cercospora leaf spot severity was not affected. Therefore, results from of this research indicate that glyphosate and glyphosate-fungicide combinations do not significantly contribute to Cercospora leaf spot control.