NDSU Crop and Pest Report
Plant Pathology


ISSUE 15   August 19, 2004

YEAR END SUMMARY: NDSU IPM SMALL GRAIN SURVEY

Except for some final surveys this week in the northeast and northcentral and northwest regions, the NDSU IPM crop scouts have finished their survey efforts for the summer. Most will be heading back to college soon. Many thanks to the NDSU field scouts (Lorilie Atkinson, Nathan Carlson, Heather Dickinson, Tammy Link, Clara Presser, Samantha Roth, Josh Seekins, and Nikki Zahradka) for their excellent efforts this year.

Thanks, also, to Jerry Schneider, Fargo North High business teacher and coach, for his work in getting the weekly data summarized and posted on the web.

The following is a summary of diseases that the field scouts observed in wheat and barley in 2004:

Wheat:

Tan spot was the first and the most common disease observed in wheat across the whole state. The vast majority of the fields had flag leaf severities less than 15%, while a few had severities greater than 30%. Septoria leaf spot was observed later in the season, primarily in the northern regions of the state, with flag leaf severities generally less than 15%. A few fields in southern counties had severities of Septoria higher than 30%. A survey of the predominate species associated with the Septoria complex on wheat across the state is being done by Dr. Tika Adhikari and Dr. Shaukat Ali of the NDSU Plant Pathology Dept.

Wheat leaf rust was observed across most of the ND counties east of the Missouri. Field scouts recorded the highest severities of leaf rust in the north central and northeast counties, with a few fields having flag leaf severities of leaf rust greater than 40%. Leaf rust occurrence was much less in the far western counties of ND.

Wheat stripe rust did occur in the state again in 2004, observed in approximately 35 wheat fields. Distribution of occurrence was east of the Missouri, but scattered across all counties in this region. Severity was generally very low, less than 1%.

Fusarium head blight (scab) in wheat was observed primarily in the Red River Valley counties and in the northeast counties. Severities generally were either below 1% or between 1-5%, but a few fields had field severities > 5%. (see figure). Some final observations on scab occurrence will be made the week of Aug. 16-20.

Other wheat diseases observed:

Spot blotch leaf spot occurred primarily in the southwest, with low incidences and severities. Bacterial leaf blight (stripe) was recorded only in northern counties and a few of these fields also exhibited the head infection phase called black chaff. Glume blotch, the head infection phase of Septoria, was observed in some fields in the eastern counties. Barley yellow dwarf was rare in 2004, only recorded in 12 fields in the northeast. Wheat ergot was observed only in 4 fields surveyed. Wheat loose smut was commonly observed in post-heading fields, and 12 fields had incidences of greater than 15%.

Barley:

The field scouts generally did not find severe barley diseases in 2004. The most common leaf spot disease observed was net blotch, with severities generally ranging between 1-15%. Spot blotch observations in barley were few. Some Septoria leaf infections were observed in barley, primarily in the northeast. Low levels of Barley leaf rust was observed in seven barley fields. Barley loose smut was commonly observed, with three fields having incidence levels greater than 15%. Fusarium head blight (scab) levels observed in barley were quite low, with the vast majority of fields with any symptoms having less than 1% field severity.

Maps indicating state wide occurrence and severity of these diseases can be found at the following web site:

http://www.ag.ndsu.nodak.edu/aginfo/ndipm/

A more thorough summary of the results of the disease survey will be made available later in the fall.

 

FINAL 2004 CEREAL RUST BULLETIN ON WEB

The USDA Cereal Lab has published the last Cereal Rust Bulletin for the year. It is available on the web at:

http://www.cdl.umn.edu/crb/2004crb/04crbfin.html

This bulletin provides an excellent summary of the occurrence and progress of leaf and stem rusts this past season on wheat, barley, and oats. For wheat leaf rust, the bulletin indicates that this disease was severe and concentrated in the upper Midwest. They indicated that losses to wheat leaf rust occurred in the most susceptible cultivars, IF they had not been sprayed with fungicide.

Marcia McMullen
Extension Plant Pathologist
mmcmulle@ndsuext.nodak.edu

 

NOW IS THE TIME TO LOOK FOR SOYBEAN CYST NEMATODES

Soybean cyst nematode infested fields were found for the first time in Richland County, ND last year. In late August through early September, the female soybean cyst nematodes should be visible on the soybean roots, if present. Above-ground symptoms, which may not always be present, can include stunted, yellow, and prematurely dead plants. To look for female nematodes on the roots, bringing a hand lens to see the nematodes, a shovel to dig the plants, and a bucket of water to wash soil off the roots will help. Female nematodes on the soybean roots will be lemon-shaped and much smaller than the nodules (Figure 1). Nematodes can be white, yellow, or brown in color depending on age. As the female nematodes are not always easy to see on the roots, sending a soil sample from suspect areas in the field to a lab may be necessary to rule out nematode damage. The NDSU Plant Diagnostic Lab as well as other labs can look for the presence of soybean cyst nematode in soil samples. A pint of soil from the top 6-8 inches of soil is generally enough for a lab. If sampling the entire field, collect soil samples in a zig-zag pattern and collect 10-20 cores per 10 acre area. If soybean cyst nematodes are found in a field, a management program should be initiated. A management program that relies on crop rotation and planting resistant varieties, will help lower the nematode population in fields. For more information on soybean cyst nematode visit the NDSU soybean disease webpage at:  http://www.ndsu.nodak.edu/soydiseases/


Fig. 1. Females of the soybean cyst
nematode present on a soybean root
(Photo courtesy G. Tylka)
.

 

STEM CANKER ON SOYBEAN

Stem canker on soybean was found in a few soybean fields last year, and has been spotted this year as well. Symptoms of stem canker consist of a reddish brown lesion at a node which can lead to death of that branch (Figure 2). In general, usually one or two branches may die prematurely due to stem canker, but usually not every branch on a plant. Planting high-quality seed and crop rotation are the main ways to manage stem canker. Some soybean varieties may be more susceptible to stem canker than others, but little information on northern soybean variety reactions to stem canker is available. If you suspect stem canker in a field, send samples to the NDSU Plant Diagnostic Lab for confirmation.


Fig. 2. Stem canker lesion on soybean
(Photo courtesy Univ. of Illinois).

Carl Bradley
Extension Plant Pathologist
carl.bradley@ndsu.nodak.edu


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