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ISSUE 16  August 23, 2001

 

CANOLA DISEASE SURVEY:  PRELIMINARY RESULTS

Data has been received on the disease levels in 194 surveyed canola fields in 21 counties of North Dakota and Minnesota. Sclerotinia continues to be the major disease problem in both states. Sclerotinia incidence (percent infected stems) reported by Jan Knodel in northwest and north central North Dakota varied from 1% in McLean County to as high as 14% in Pierce, 10% in Renville, 9.5% in McHenry and 9% in Bottineau Counties.

Incidence reported by Roger Ashley in southwest North Dakota , in Hettinger County, was nearly 8%.

Incidence reported by Nels Peterson, Mike Liane, Scott Knoke and Art Lamey in northeast North Dakota ranged from 12.8% in Benson County and 13.8% in Nelson County to as high as 20% in Cavalier County and 28.8% in Ramsey County.

Incidence reported in Red Lake County, MN, by Zachary Fore was 6%. Incidence in two fields surveyed by Russ Severson in West Polk County, MN, averaged 32.5%.

Incidence data was taken on fields at random, regardless of whether the fields were sprayed with fungicide or not. Most fields known to have received a fungicide had minimal incidences. Individual fields, assumed to be unsprayed, had incidences as high as 65% in Cavalier County and in Ramsey County; other individual fields had incidences as high as 30-50%. The overall incidence in northwest and north central North Dakota was about 7%; the incidence in the rest of the state and in Minnesota was over 15%.

Aster yellows, which was common in 1999 and 2000, was uncommon in 2001. One field with a moderate level of incidence was reported in Cavalier County and another in Ramsey County.

Blackleg incidences were generally low, but incidences in individual fields were as high as 12.5% and 27.5% in Cavalier County and 15% and 20% in Pierce County.

Alternaria black spot of the pods was generally low in all areas.

Additional data will be gathered in the next week or two.

Art Lamey
Plant Pathologist Emeritus

alamey@worldnet.att.net

 

SMALL GRAIN DISEASE AND INSECT SURVEY - PRELIMINARY SUMMARY

Six NDSU IPM field scouts surveyed over 1500 small grain fields in ND this summer. The vast majority were wheat or durum fields, but barley and oats also were included. The following is a brief initial summary of the results of that survey. A more complete summary of survey results will be available in the Table of Contents Issue of the Crop and Pest Report, that will be published in September.

Initial disease detections on 1-5 leaf wheat consisted primarily of tan spot in wheat and spot or net blotch in barley. Leaf rust was detected on winter wheat in Sargent and Benson counties in mid-June, but was not detected in spring wheats until the first week of July, in SE and SC counties. Leaf rust levels remained low until the first part of August, when severity levels became as high as 35% on flag leaves on late planted spring wheat. A table of leaf rust severities on spring wheat cultivars in ND and MN in 2001 can be found on the USDA Cereal Disease Lab website:

http://www.cdl.umn.edu/germplasm/survey/MN_ND2001.html

The ND ratings were done by Dr. Jack Rasmussen, NDSU Dept. of Plant Pathology.

Septoria leaf blotch became frequent and severe on spring wheats and durums as the crops went into heading and grain fill, with incidences of 100% and severities of 40-60% not uncommon. Glume blotch, the head infection phase of Septoria, also was observed in some fields. The virus diseases of barley yellow dwarf and wheat streak mosaic were observed very infrequently in the field surveys. The grain aphids that carry and transmit barley yellow dwarf also were infrequently observed. Loose smut was observed in a moderate percentage of fields surveyed, with incidences often ranging from 2- 10%. Diseases of export concern, such as flag smut and dwarf bunt, were NOT found in the survey, nor were cereal leaf beetles.

Wheat head scab infections were frequent and in some cases severe in the NE, NC and NW districts Head scab field severity generally was much less in barley than that found in wheats. Some examples of head scab observations from the NC and NW districts the week of Aug. 13: Nathan Carlson surveyed in McLean , Mountrail and Williams counties and observed head scab in all 15 spring and durum wheat fields he surveyed. Incidence of plants infected ranged from 4 - 82%; head severity ranged from 7-34%. Kelly Novak surveyed in Ward, Renville, Burke, and Divide counties and found head scab in all of the wheat and durum fields surveyed that were past watery ripe stage. Incidence ranged from 2-66%; head severity ranged from 3-21%. Across the 7 counties, the highest field severity (incidence x head severity) was 20%; the range was 1-20%. Of two barley fields, one had no scab observed, the other had a field severity of 2.2%. Subsequent summaries of head scab levels will take into account class of wheat, growth stage at time of survey observation, and date of survey observation. Scab severities will vary according to heading date and according to growth stage at time of evaluation. Scab evaluations determined at early kernel development result in lower severity ratings than those taken at soft to mid-dough. Scab severities may also vary according to wheat class.

 

PRELIMINARY RESULTS FROM SCAB FUNGICIDE TRIALS AND CULTIVAR EVALUATIONS

Uniform fungicide trials to evaluate products for their efficacy against Fusarium head blight (scab) again were conducted in ND, this year at Fargo, Langdon, Carrington, and several locations in the NC region. Included in the trial were Folicur, Tilt, several experimental products and a biological. The following are preliminary results from several locations, showing field severity of scab only.

Scab Field Severity Values in 2001 ND Uniform Fungicide Trials - some preliminary results

Treatment

Fargo HRS*

CREC Durum*

Garrison Durum*

Untreated

5.7

42.1

14.9

Folicur 4 fl oz

3.3

8.3

6.7

AMS2119 5.7 oz

3.5

6.7

5.4

BAS 505 0.4 lb

3.4

7.2

6.4

BAS 505 + Fol. 0.2 lb + 2 fl oz

2.8

5.3

5.0

Tilt 4 fl oz

--

16.6

10.0

Yeast

3.9

33.3

11.6

*Scab field severities = incidence x head severity; Fargo site of Marcia McMullen on Oxen wheat; CREC = Carrington results on durum, research by Blaine Schatz and Greg Endres; Garrison durum results of Kent McKay; NCREC, Minot.

Kent McKay, NDSU Extension Area Specialist, North Central Research Extension Center, and I rated cultivars for scab severities at Ross and Columbus, ND on Aug. 8, when most spring wheat cultivars were in the mid-dough stage, and durum cultivars were in the early dough stage. We rated one replicate at each site. The following is a summary of scab field severity (FS) ratings at Ross in Mountrail county. Similar results were observed at Columbus and higher severity ratings were recorded at Mohall.

Scab field severity ratings at Ross, ND, 2001

HRS cv

Scab FS*

Durum cv

Scab FS*

Argent

39.8

Voss

25.0

Gunner

12.8

Navigator

36.8

Parshall

18.1

Vic

37.2

Amidon

52.1

Belzer

9.8

Alsen

10.8

Pierce

22.8

Trenton

35.1

Kari

26.3

Keene

37.6

Lebsock

11.4

Reeder

22.9

Ward

31.6

Dandy

34.5

Munich

30.3

Ember

16.6

Kyle

24.4

Scholar

42.6

Avonlea

37.4

McKenzie

55.3

Renville

23.5

McNeal

43.5

Plaza

17.8

Norpro

32.4

Mountrail

25.8

   

Monroe

45.3

   

Pathfinder

22.5

   

Melita

26.9

   

Ben

16.3

   

Maier

13.7

* FS = field severity of scab = incidence x head severity

 

POTATO LATE BLIGHT HOTLINE

As of August 20, late blight was confirmed from a field near Lisbon in SE ND. The late blight was limited to a small spot in the field. A new report of late blight was confirmed from a field in Pembina, ND, as of August 21. Growers in these areas should scout fields, destroy small areas of late bight infections and continue fungicide applications. Late season applications of Gavel or tin fungicides may reduce tuber infection in late blight infected fields. Conditions for late blight remain favorable at all irrigated sites and for Stephen of the non-irrigated sites, but for other non-irrigated sites, conditions remain unfavorable for late blight development.

 

SUNFLOWER DOWNY MILDEW SURVEY

The NDSU IPM scouts also surveyed 90 sunflower fields for the presence of downy mildew. Downy mildew infected plants were observed in 47.8% of these fields, with percent plants infected in a field ranging from 0.5% to 42% (a field in Ward county). The average % infected plants in positive fields was 4.6%. Dr. Tom Guyla, USDA sunflower pathologist, identified downy mildew to race from some of these fields. All but one sample had races that were Apron resistant. He identified four different races that appeared to be evenly distributed across the state.

Marcia McMullen
Extension Plant Pathologist

mmcmulle@ndsuext.nodak.edu


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