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North Dakota Wheat Disease Survey, 2004
Marcia McMullen, Extension Plant Pathologist, North Dakota State University, Fargo, ND Roger Ashley, Area Extension Agronomist, Dickinson Research Extension Center, Dickinson, ND Greg Endres, Area Extension Agronomist, Carrington Research Extension Center, Carrington, ND Phil Glogoza, Extension Entomologist, North Dakota State University, Fargo, ND Terry Gregoire, Area Extension Agronomist, Devils Lake Area Office, Devils Lake, ND Jan Knodel, Area Crop Protection Specialist, North Central Research Extension Center, Minot, ND
Introduction: The purpose of the wheat disease survey is to detect the presence and severity of leaf and head diseases that are common in North Dakota and to verify the absence of diseases that might be of export concern. Survey information is provided on a timely basis to ND producers to assist them in disease management decisions.
Materials and Methods: Field scouts surveyed for leaf and head diseases of winter wheat, hard red spring wheat, and durum wheat. Fields were surveyed in all 53 counties. Survey scouts operated out of the Dickinson Research Extension Center, the North Central Research Extension Center, the Carrington Research Extension Center, the Devils Lake Area Extension Office, and the Fargo Experiment Station.
Crops were surveyed from the two-leaf stage through kernel mid-dough stage. In each field, the field scout examined five locations along a W pattern, 10 main stems per location, for a total of 50 plants. Incidence was recorded as % of main stems showing symptoms, while severity was based on % leaf or head area showing symptoms. The % of fields showing symptoms of a particular disease out of the total surveyed also is reported.
Results: A total of 1471 wheat fields were surveyed in 2004, across all ND counties. The numbers represented approximately one field surveyed per 6000 wheat acres/county. Surveys began on May 26 and continued through August 19. The August date surveys were primarily in the northeast and north central crop reporting districts where crops were later to mature.
Wheat leaf rust (Puccinia triticina) was found in 363 or 24.7% of all fields surveyed. Leaf rust was found in all but six counties; primarily absent in the southwest and common in the east (Fig. 1). The average wheat leaf rust severity across all fields was 4.9%. Leaf rust was slightly more common in 2004 than in 2003, but average severities were slightly lower.
Tan Spot: Tan spot (Pyrenophora tritici-repentis) was the most frequently occurring disease observed on wheat, found in 60% of all fields surveyed (Fig. 2). The average severity of tan spot in infected fields was 3.8%. The highest average severities generally were found in the southwest and south central counties.
Septoria Leaf Disease Complex: The Septoria leaf disease complex (Septoria tritici, Stagonospora nodorum, Stagonosopora avenae f. sp. triticea) was observed in fewer fields than tan spot (15.7% vs 60%), but the statewide average severity was higher (9.4% for Septoria vs 3.8% for tan spot). Septoria infections were primarily observed in the northeast and north central regions (Fig. 3), and were primarily observed in fields surveyed after flag leaf emergence.
Fusarium head blight (scab): Symptoms of Fusarium head blight (scab) were observed in 33.5 % of the 439 post-flowering fields surveyed (Fig. 4 = > Zadoks growth stage 71 = post flowering), a slightly higher percentage of fields with symptoms than in 2003, but overall severity was still low. For fields showing symptoms, the average % of heads with symptoms was 10.7% and average field severity (% heads with symptoms x head severity) was 1.4%. Fields with the most frequent observations of scab were in the east. Other Diseases Observed:
Stripe rust: Stripe rust (Puccinia striiformis) was observed in 34 fields across the state, similar to 2003. Severities were generally low, except in one field in Cass Co.
Spot blotch: Spot blotch (Cochliobolus sativus) was observed on leaves of wheat in 3.6% of all wheat fields surveyed, primarily in the southwest counties. This leaf spot disease is generally favored by warm, drier conditions than other common fungal leaf spot diseases of wheat, so levels dropped in 2004.
Bacterial leaf blight (stripe) and Black Chaff: Bacterial leaf blight was observed in 5.2% of fields surveyed, and black chaff, the bacterial head infection, was observed in <1% of fields surveyed after heading. The fields with symptoms of bacterial infection were all located in the northern tier of counties.
Loose smut: Of the post-headed fields surveyed, 42.4% had symptoms of loose smut, a slightly higher percentage than in 2003. The average % heads infected in these fields was 4.7%, and 12 fields had incidence levels greater than 15%.
Barley Yellow Dwarf Virus (BYDV): BYDV was observed in only 1.1% of the fields surveyed, predominately in the northeast, an area where grain aphid populations also were relatively high. Grain aphids transmit this virus.
Diseases Not Observed in Survey: The following diseases were not observed in the 2004 wheat survey: Wheat streak mosaic virus; stem rust; flag smut; dwarf bunt; and Cephalosporium stripe.
Acknowledgements: The authors wish to thank the ND Dept. of Agriculture, the ND SBARE Wheat Research Granting Committee, and the ND Wheat Commission for financial support of this survey effort on wheat. Many thanks to the field scouts of 2004: Lorilie Atkinson, Nathan Carlson, Heather Dickinson, Tammy Link, Clara Presser, Samantha Roth, Josh Seekins, and Nikki Zahradka. Thanks also to Jerry Schneider, data analyst.
Maps of occurrence of wheat diseases in 2004 may be found at the following web site: http://www.ag.ndsu.nodak.edu/aginfo/ndipm/
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Last Updated:
Tuesday, July 05, 2005 10:26:36 AM
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