NDSU Crop and Pest Report
Plant Pathology


ISSUE 14   August 5, 2004

NDSU IPM SMALL GRAINS SURVEY UPDATE, JULY 26-30, 2004

The NDSU IPM field scouts surveyed 115 wheat and 14 barley fields in North Dakota the week of July 26 to July 30. The majority of the wheat was in the milk to dough stage of development, but several fields also were ripening and some in the Northcentral region were still in the flowering stages (see figure).

In barley, most fields were in dough to ripening stages. The majority of barley fields are becoming too mature to survey.

In wheat, tan spot and Septoria were common on flag leaves, with severities primarily in the 1-15% range. Some glume blotch, caused by Septoria infections on the grain head, were observed in 10% of the wheat fields surveyed.

Five fields of wheat in the northcentral region showed symptoms of low levels of stripe rust. Wheat leaf rust continues to be found scattered across the state, in 39% of the fields surveyed.. A majority of the fields had leaf rust severities under 15%, but one spring wheat field in Nelson county had a severity of 50%.

Fusarium head blight (FHB = scab) was observed in 32.5% of the post-flowering wheat fields surveyed (versus 20% the previous week).

Field severity indexes of FHB ranged from <1% up to between 6 and 10%. The majority of observations were in the NE and EC regions, where rainfall has been the greatest and the Fusarium head blight risk map has indicated high risk over a fairly long period.

In barley, fungal leaf spots of Septoria, net blotch and spot blotch were observed, but continued to be at low levels in most fields. Only one of the 14 barley fields surveyed in the past week had symptoms of scab, and that was in Nelson county.

 

SMALL GRAINS DISEASE FORECASTING MODEL - FHB RISK

Many NDAWN locations in the northeast and northcentral regions of North Dakota indicated a higher risk potential for Fusarium head blight infections over the July 21-24 period than in the subsequent week. A few examples are given in the following table.

Site

July Date and % Risk of serious FHB (scab)

7/21

7/22

7/23

7/24

7/25

7/26

7/27

Mohall

65

71

67

63

56

55

48

Berthold

77

79

72

70

65

57

58

Cando

73

73

69

65

61

61

56

The July 21-24 period may have coincided with flowering in some fields in those parts of the state, and scab infections from that time period may be evident now.


Our NDSU IPM survey will pick up field infections of scab, but additional observations from crop consultants, county agents, and private agronomists are welcome, as this kind of information helps us validate the reliability of the disease risk model. If you have information to share on incidence and severity of scab plus flowering date, please let me know.

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


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