NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
October 21, 1999
The 1999 survey of canola diseases showed that Sclerotinia stem rot continues to be the most serious disease problem in North Dakota and Minnesota. As this region's canola industry continues negotiations with the Environmental Protection Agency regarding registration of additional fungicides to fight the disease, the annual surveys have become an important tool, says a specialist with the North Dakota State University Extension Service.
"There certainly is a need for fungicides to help manage Sclerotinia," says Art Lamey, an extension plant pathologist at NDSU. "These annual surveys have substantiated our argument."
Full registration of the fungicide Quadris to control Sclerotinia in canola came in time for the 1999 production season, but first-year results were variable, according to some growers. Lamey says weather delays resulting in late application may have been responsible for some of the variability.
"Canola producers did have a chance to prepare this year, and at least in some cases, the fungicide seemed to help," Lamey adds.
The average Sclerotinia incidence was 13 percent for North Dakota in 1999, about the same level as in 1998, Lamey says. Minnesota's 1999 average was 15 percent, up from 11 percent in 1998 but below the 1997 level of 19 percent.
"The Minnesota numbers just show how much variability environmental conditions bring about," Lamey says.
North Dakota's Sclerotinia hot spot for 1999 was Ramsey County, which had a 29-percent incidence level. Minnesota's Kittson County had a 26-percent incidence level. Lamey says the counties with the worst Sclerotinia problem in 1999 had long histories of canola production. In addition, some canola producers in those counties use shorter rotations than other producers. Also, environmental conditions were optimal for Sclerotinia development in the hardest-hit counties. Other North Dakota counties with significant Sclerotinia incidence levels in 1999 were Cavalier (19.8 percent), Wells (18.8), and Benson (16.9), and in Minnesota, Roseau County (18.1).
"Other factors affecting Sclerotinia infection include the concentration of susceptible crop acres and the intensity of the disease in previous years," Lamey says. "So, canola producers may want to spend some time this winter studying the disease's history in their area and talking to their neighbors to get a feel for next year's planting intentions. This information can help enhance cultural practices to manage the disease."
For the 1999 growing season, Blackleg generally appeared to be more of a problem in counties farther west in North Dakota, Lamey says. McHenry County had highest average incidence, 9.6 percent.
"The growers have some choices when it comes to Blackleg management that we really don't have with Sclerotinia," Lamey says. Options for controlling Blackleg include burying crop residue, rotation (three years on the same field and nearby fields), and varietal selection.
This year, surveyors observed aster yellows in 35 percent of the fields they surveyed in North Dakota and in 22 percent of the surveyed fields in Minnesota, but they made no effort to determine severity levels, Lamey says.
"In previous years, we didn't really notice any aster yellows," Lamey says. "Late planting could very well have contributed to aster yellows, but entomologists also reported an increase in aster leafhopper numbers this year, and the leafhopper is responsible for transmitting the disease. So, the appearance of aster yellows in 1999 canola fields is probably the result of timing and more leafhoppers."
The 1999 disease results are based on 135 fields surveyed in 14 North Dakota counties and 41 fields located in five Minnesota counties, for a total of 176 fields. Lamey says the survey techniques have been adapted from those used in Saskatchewan. Working with Lamey on this year's survey were Kent McKay, Janet Knodel and Greg Endres, all area specialists with NDSU Extension Service, and Karen Andol and Zachary Fore with the University of Minnesota Extension Service.
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Source: Art Lamey (701) 231-7056
Editor: Dean Hulse (701) 231-6136