ISSUE 4   June 5, 2008

WHEAT STREAK MOSAIC VIRUS AND HIGH PLAINS VIRUS-MORE SAMPLES

The NDSU Diagnostic Lab last week received winter wheat samples from several locations across the state that were either positive for Wheat Streak Mosaic Virus (WSMV), High Plains Virus, or for both. The level of severity of symptoms in the fields varied, from only scattered plants infected to portions of the field having severe symptoms. Last week’s Crop and Pest Report contained a story about WSMV, its symptoms and management options, so please see that article for further information.

High Plains Virus is a relatively new disease confirmed in the state, but this virus in wheat is also transmitted by the wheat curl mite, the degree of injury is similar to that caused by WSMV, the symptoms are similar, and the management of this virus is similar to steps to needed for WSMV.

A good summary of the two virus diseases is available on-line, in an article by plant pathologists from Oklahoma State University. The web address is:

http://entoplp.okstate.edu/ddd/diseases/wsmv-hpv.pdf

This publication also has a table that estimates yield losses caused by wheat streak mosaic virus in three winter wheat cultivars. For example, in Oklahoma, in the winter wheat cultivar ‘Chisholm’:

Time of infection

WSMV severity
(0-3)*

Yield
(bu/A)

Fall

2.7

19

Spring

1.3

42

Not infected

0

51

* Severity rated on scale: 0 = no symptoms; 3 = severe symptoms (Source: Bob Hunger, OKSU)

 

EARLY SEASON TAN SPOT

With the recent rains in some locations across the state, the NDSU small grains disease forecasting site indicates some favorable infection periods for tan spot of wheat. Growers with wheat in the herbicide application stage at these locations may want to consider applying fungicides in conjunction with their herbicides for tan spot control, especially where wheat has been planted into wheat stubble.

tan spot

A large number of fungicide products are available that do a good job against early season tan spot. Generally, when tank mixed with herbicides, additional adjuvants are not needed.

The NDSU disease forecasting site, that provides information on risk of tan spot, is available at:

http://www.ndsu.edu/scabforecast

The leaf disease predictions are obtained with a 3 step process:

1) choose the nearest NDAWN station and highlight;
2) click on the leaf disease stages of the crop;
3) click on get forecast

The scab forecast information, which we should not have to think about yet, is only achieved by clicking on the flowering growth stage.

 

DISEASE AND INSECT SURVEY BEGINS

NDSU IPM Field Scouts were trained on survey procedures on May 28th at the Carrington Research Extension Center. These field scouts will be looking for major disease and insect pests in wheat, barley, soybean, canola, and sunflower across the state. Their goal is to identify the distribution and severity of the major pests, in order to alert producers of any management needs, as well as verify that our field crops don’t have pests of export concern.

The 2008 field scouts are:

Andrew Friskop, Hankinson, ND native, surveying in the southeast and east central counties (Marcia McMullen, Sam Markell, and Jan Knodel coordinators, NDSU Plant Pathology and Entomology);

Amanda Schoch, New England, ND native, and Kayla Hutzenbiler, Belfield, ND native, surveying in the southwest and west central counties (Roger Ashley coordinator, DREC);

Taylor Mattson, Carrington, ND native, surveying in the central and south central counties (Greg Endres coordinator, CREC);

Tracy Samson, Max, ND native, surveying in the north west and north central counties (Denise Markle coordinator, NCREC);

Valerie Wilson, Edmore, ND native, surveying in the northeast and several north central counties (Mike Liane coordinator, Devils Lake Area Extension Office).

Last year, the NDSU IPM scouts surveyed over 1100 wheat fields, 318 barley fields, 268 soybean fields, 130 sunflower fields, and 156 canola fields. Highlights of the 2007 survey included: an increased detection of wheat leaf rust and wheat stem maggot in wheat, very low levels of Fusarium head blight in wheat and barley, the absence of soybean rust, relatively low populations of soybean aphid and canola flea beetle, and high populations of banded sunflower moth.

Marcia McMullen
Extension Plant Pathologist
marcia.mcmullen@ndsu.edu

 

FIRST REPORT OF SOYBEAN RUST IN LOUISIANA

On May 27th soybean rust was found approximately 50 miles south of Baton Rouge, Louisiana, near the small town of Jeannerette. The disease was observed Kudzu, a common weed in parts of the south. Although the incidence was low, the severity on the leaves with rust was approximately 50%. This is the first report of Soybean Rust in Louisiana in 2008.

Confirmation of soybean rust in Louisiana is not a surprise; the disease has appeared in the state in previous years. Soybean rust has already been confirmed in Texas on Kudzu. Spores from both finds will likely blow north and infect soybeans as the crop emerges. We will be tracking the disease as it progresses northward in 2008. At this point, the soybean rust finds have little impact on North Dakota. However, it is best to be aware of the disease development to our south. We will provide updates as things change. Further information is available at http://www.sbrusa.net.

Sam Markell
Extension Plant Pathologist
samuel.markell@ndsu.edu


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