NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

May 20, 1999

Producers Warned about Diseases in Late-Planted Wheat

Planting wheat later than normal has helped some producers sidestep troubles with Fusarium head blight (scab) in recent years. However, while the threat from scab subsides, late planting increases the risk from two other diseases affecting wheat: leaf rust and barley yellow dwarf virus. For that reason, a specialist at North Dakota State University says wheat producers who still have crop to plant should be reassessing their options.

"In 1998, spring wheats showed some variation in susceptibility to leaf rust, as recorded at several locations in the eastern part of North Dakota," says Marcia McMullen, extension plant pathologist and integrated pest management (IPM) coordinator at NDSU. "Among the wheats showing the most rust were Forge, AC Majestic, Ingot, AC Barrie, Lars and 2375. Durums have a slow-rusting reaction to leaf rust and generally aren't damaged much."

Wheat leaf rust does not overwinter in this region, McMullen says. Instead, the disease develops on wheats in the southern plains states, and then fungal spores produced by the disease are carried north by prevailing winds. Late-planted spring wheat is more at risk because the fungus has longer to build up into high populations. Also, younger plants are more easily damaged by the rust.

"This year leaf rust has been reported as being more severe in Texas and Oklahoma," McMullen says. "If rust appears to be developing in our region, there are a number of fungicides available for leaf rust control."

Similarly, barley yellow dwarf virus can create problems for late-planted wheat, oats and barley. This virus is transmitted by grain aphids, which also blow into the region during the summer months from southern states, McMullen says.

"If these aphids arrive when the grain has reached the flag-leaf stage or beyond, generally the virus doesn't do much damage, other than cause some yellow-tipped flag leaves," McMullen explains. "But in late-planted grain that often becomes infected at a younger stage of development, the virus gets established in the plant and can cause severe stunting and yellowing, with poor grain fill. Last year, some late-planted spring wheat in northeast North Dakota did become severely infected with barley yellow dwarf virus and yielded poorly."

This past winter some testing of regional wheat varieties for response to barley yellow dwarf virus infection occurred at a USDA-Agricultural Research Service lab at the University of Illinois, McMullen says. Coordinating that effort were Terry Gregoire, area extension specialist for cropping systems in Devils Lake, and Mike Edwards, a USDA-ARS virologist in Fargo.

The Illinois researchers grew out seed of eight varieties to test for barley yellow dwarf virus on plants. Based on those limited results, it appears that Russ, Hagar, 2375 and AC Barrie may be more susceptible to barley yellow dwarf virus than the other varieties tested, McMullen says. In contrast, the more tolerant spring wheat varieties in the sample were AC Majestic, Gunner and HJ98. Ben durum also displayed tolerance to barley yellow dwarf virus.

"The NDSU Extension Service will be keeping tabs on the development of aphids and barley yellow dwarf virus in states to our south," McMullen concludes. "If aphids appear to be a threat to late-planted grain, a number of insecticides are available to control their populations."

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Source: Marcia McMullen (701) 231-7627

Editor: Dean Hulse (701) 231-6136