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Pathologist urges considering sugarbeet disease resistance before ordering seed
December 05, 2007
Sugarbeet growers, facing new seed variety choices for next spring's planting, need to keep the importance of disease resistance high on their list of requirements, says a Montana State University plant pathologist.
Sugarbeet growers will be considering the potential of relatively new options like Round Up Ready varieties as well as traditional concerns like disease resistance," said Barry Jacobsen, MSU plant pathologist. "One of those considerations should be that we have limited control of some diseases other than the resistance bred into sugarbeet varieties."
For some areas of the state, disease resistance is paramount, he added.
"In the Western Sugar Factor District along the Clark's Fork, Yellowstone and Big Horn River Valleys, and in the Sidney Sugars production area in the Mile City, Terry, Fallon and Glendive areas, growers should only select varieties with resistance to the rhizomania and curly top viruses.
Seed treatments to control disease are only partially effective, he added. "While Poncho seed treatment will help control curly top, it only does so with varieties having a moderate level of resistance," he said. That assessment is based on the last three years of research at the Southern Agricultural Research Center at Huntley. Research data from North Dakota has shown that Poncho also provides control of root maggot, flea beetles, wireworms and springtails.
"Fusarium yellows" is another disease that should be a priority for growers anywhere in Montana, Jacobsen added. There are no controls for this disease other than variety resistance. Screening trials in 2006 and 2007 indicated that some newly approved Round Up Ready varieties are very susceptible to this disease.
Fusarium yellows is caused by a soilborne fungus. Once the fungus infests soil, even long term rotations are of little help, he said.
In addition, growers with cyst nematode infestations should select varieties with high levels of resistance to fusarium yellows, because the nematode causes this disease to be more severe. MSU research has shown that Tachigaren seed treatment reduces losses on varieties with moderate levels of resistance.
Resistance of cercospora leaf spot is required in the Sidney Sugars production area, and this has been a major factor in reducing the need for fungicide applications and reducing losses to this disease. Western Sugar growers east of Pompeys Pillar should consider selecting varieties with at least moderate resistance. Resistance to this disease is measured on the "KWS scale," and varieties with ratings less that 5.3 should be considered moderately resistant.
"Selection of these varieties will not eliminate the need to use fungicides, but will generally save one or two fungicide applications," Jacobsen said.
There are high yielding varieties with moderate levels of resistance to aphanomyces black root rot. However these varieties provide better stands and higher yields if growers also have them treated with Tachigaren fungicide seed treatment. Growers can select either the 20 or 45 gram per seed unit rate. If the higher rate is selected, it must be only applied to pelleted seed. MSU research has shown that the 20 gram rate is nearly equal to the 45 gram rate in reducing losses to this disease in Montana.
Recently, varieties with resistance to the sugarbeet cyst nematode have become available and only some of these have the virus and fusarium yellows resistance needed for successful production.
"Where these cyst nematode varieties that lack either curly top or fusarium yellows resistance have been planted, serious losses have occurred," Jacobsen said.
Resistance to rhizoctonia crown and root rot is available, Jacobsen said, but MSU research clearly demonstrated that growers will have higher yields and better disease control by selecting varieties with high yield potential, and resistance to other critical diseases, then use Quadris fungicide at the four-to-eight leaf stage.
Information on disease resistance is available from seed dealers and sugar company representatives.
Western Sugar will host a series of seed seminars for growers that will cover Round Up Ready varieties and disease resistance. The first meeting will be at the Southern Agricultural Research Center office building at Huntley on Tuesday, Dec. 11 starting at 9 a.m. A second meeting Dec. 11 will be at the Hardin Depot starting at 2 p.m. On Wednesday Dec. 12 similar meetings will be held in Laurel at the Best Western starting at 8:30 a.m. and at Powell, Wyo. at the Eagles starting at 2 p.m.
Contact: Barry Jacobsen (406) 994-5161 or uplbj@montana.edu
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