NDSU Crop and Pest Report
Plant Pathology


ISSUE 12  July 17, 2003

ND IPM DISEASE SURVEY, UPDATE FOR 7/7-7/11

The NDSU IPM scouts examined 102 wheat and 28 barley fields the week of July 7-11, for insect and disease pests. The maturity of the fields ranged from early leaf stages in the NW to soft dough in the south and east central and central counties.

(see following figure for locations and growth stage of wheat crops surveyed, 7/7-7/11, 2003.)

IPM Survey map

Wheat leaf rust was observed in 14% of the wheat fields, primarily confined to the east central and south central regions of the survey.

IPM Survey map

Two fields also showed symptoms of stripe rust, one in Sioux and one in Stutsman county. Tan spot and Septoria blotch were observed on the top leaves of crops in 73% of the fields surveyed, with Septoria being dominant in more mature fields and having an average severity of 2-5% on the flag leaves.

Head scab was observed in 7 of the 47 post-flowering fields surveyed, with scattered plants infected and the field severity index averaging between 0.1% to 1% in these fields.

Barley yellow dwarf virus was observed in 45% of the fields surveyed in the NE counties, indicating infection resulting from high aphid populations in that region.

Loose smut was observed in 21% of wheat fields surveyed, with average incidence from 2-4%, but some fields with incidences as high as 30%. The high incidence of loose smut indicates the need for growers to know their seed source next year and the need for seed treatment.

In barley, 18 of the 28 fields surveyed were in the milk to dough stages of kernel development. Growth stages of barley surveyed from 7/7- 7/11.

IPM Survey map

The leaf spots fungi causing net blotch, Septoria, or spot blotch were commonly observed, with severities on flag leaves averaging between 1 and 5%. Barley leaf rust was observed in two surveyed fields.

Loose smut was observed in 18% of the barley fields, with average incidences of 2-4%. One surveyed barley field in Slope county had head scab and 18% of the barley fields showed symptoms of BYDV, primarily in the NE.

 

DISEASE RATINGS ON WINTER WHEAT AT ELENDALE AND LISBON, ND

An evaluation of winter wheat varieties at a Ducks Unlimited winter wheat plot at Elendale, ND on July 1 indicated some substantial differences in susceptibility among varieties to infection by Septoria (Stagonospora nodorum) and leaf rust.

Disease severity in untreated plots of Winter Wheat at Elendale, ND 2003 (2 rep means)

Variety

% Septoria on flag leaf

% Leaf Rust on flag leaf

Jagalene

7 b

0 c

Wesley

9 b

5 c

Arapahoe

12.5 b

2 c

CDC Falcon

32.5 b

0 c

Jerry

25 ab

5 c

Nekota

17.5 b

30 a

Wahoo

7.5 b

5 c

Expedition

11.5 b

20 b

Harding

6.5 b

0 c

Millennium

9 b

0 c

The above disease severity ratings were taken on July 1, at early dough. Disease severity on CDC Falcon plots at Lisbon increased substantially in one week’s time, from July 1 to July 10. Septoria leaf spot severity on the flag leaf of non-fungicide treated CDC Falcon plots averaged 25% on July 1 and increased to 75% by July 10. Various fungicide treatments on these CDC Falcon plots reduced leaf disease severity by 75 to 91%. Reports on fungicide results will be made available after harvest.

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

 

AMISTAR FUNGICIDE LABELED FOR BROADLEAF CROPS

Amistar fungicide, which contains azoxystrobin as the active ingredient, is a new product available from Syngenta. The active ingredient, azoxystrobin, is the same as in Quadris fungicide, but at a different concentration (80% a.i. Amistar; 22.9% a.i. Quadris). Crops grown in North Dakota that Amistar is registered on include dry bean, chickpea, potato, and sugarbeet.

Carl A. Bradley
Extension Plant Pathologist
cbradley@ndsuext.nodak.edu

 


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