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ISSUE 16  August 27, 1998

 

WHEAT DISEASES SURVEY

    The following information is a preliminary summary of the 1998 wheat survey. Special thanks go to the three crop scouts who conducted this survey: Carrie Buttke, Shane Crawford, and Sarah Gelhlar. Over 600 wheat fields were surveyed for the presence and severity of leaf and head diseases. Nine of these fields were winter wheat, 136 were durum, and 477 were hard red spring wheat. Eight of the nine crop reporting districts were represented in the survey. In the west central (WC) district, only McLean county was included in the survey.

    The fungal leaf spots, tan spot and Septoria, were present in almost 100% of the fields surveyed at flag leaf stage or beyond, regardless of wheat class. Leaf spot diseases were detected at early growth stages in wheat fields planted into wheat stubble, and by late dough stage, some fields had 75-100% of the flag leaf infected.

    Wheat leaf rust was found in 39.4% of the fields surveyed. Districts that had the highest prevalence of fields showing detectable leaf rust infections were the SE, EC, and Central districts (see Table). However, the average percent severity of leaf rust on the flag leaf was the highest in the NE district. The higher severity in this NE district most likely was due to the fact that AC Barrie hard red spring wheat was a common variety in this district and this variety showed considerable levels of leaf rust in 1998. Leaf rust was most frequently observed on hard red spring wheats, and only rarely occurred on durums. Leaf rust was detected as early as June 2 on two-leaf wheat.

Wheat Leaf Rust Table

 

District

# of fields surveyed

% with
leaf rust

Avg. % severity
on infected
flag leaf

EC

100

62.00%

4.90%

SE

68

71.00%

5.20%

C

78

63.00%

6.80%

SC

18

44.00%

1.40%

NE

92

41.00%

11.20%

NC

81

27.00%

5.80%

WC

35

24.00%

1.60%

NW

150

7.00%

3.20%

    *Only McLean County surveyed

   Thirty-eight percent of the 622 fields surveyed were surveyed post-flowering. Of these post-flowering fields, 83.4% showed symptoms of head scab, with field severity ranging from 0.1% up to 67.5% (see Table). The WC and NW districts had the lowest frequency of fields showing some scab symptoms. Field severity of head scab averaged the highest in the NC and NE districts. The highest scab severities generally were found in durum fields in the NC and NE districts, but one field of durum in the NW district also had severe scab.

Wheat Scab (Fusarium head blight)

District

% of Post/
Flowering Fields with
symptoms

Avg. Field Severity *

Range of
Field
Severity

EC

90.30%

2.5

0.3-9.4

SE

88.20%

3.7

0.3-5.0

C

94.70%

2.8

0.1-8.6

SC

100.00%

1.4

0.3-4.0

NE

96.00%

5.9

0.1-55.0**

NC

69.40%

6.1

0.3-35.0**

WC

50.00%

2.6

0.3-6.6**

NW

68.20%

5.7

0.1-67.5**

*Field severity =Incidence (% of tillers with symptoms) x head severity (=% head showing symptoms)
**Highest scab severity found in durums.

Marcia McMullen
Extension Plant Pathologist

 

BARLEY DISEASE SURVEY

    Along with the wheat survey, a barley survey was conducted across a portion of the state. The survey’s range covered the northeast, stretching west to Ward county, and south to Cass county. All fields were in the late soft to early hard dough stage, and were examined for the presence and severity of leaf and head diseases.

    Net blotch and septoria occurred in nearly 100 % of the fields with severities being greatest in fields planted into barley stubble. Leaf rust showed up in the later fields primarily in the North Central region.

    Scab was present across the range of the survey with the highest severities observed in the northeastern most counties. The later crop showed slightly less severe scab infestations.

Barley

Scab Field Severity/County

Barnes

1.3%

Ramsey

1.1%

Benson

1.3%

Renville

0.5%

Bottineau

0.1%

Steele

1.2%

Cass

2.5%

Towner

2.0%

Cavalier

5.7%

Trail

1.8%

Grand Forks

0.8%

Walsh

1.2%

Nelson

4.2%

Ward

0.3%

Pembina

3.5%

   

Jeremy Pederson
Extension Barely Technician

 

CANOLA DISEASE SURVEY

    Most of the canola disease survey was completed by last week with the help of crop surveyor Carrie Buttke. Surveys were conducted in Benson, western Cavalier, Ramsey, Rolette, Stuttsman, Towner and Wells Counties, with 9 fields examined in Benson County, 13 in western Cavalier County and 10 in each of the other counties surveyed. Each field was examined when the crop was in the swath. Eight random stops were made in each field and 5 stems examined per stop for blackleg and Sclerotinia. Ten pods were examined for black spot at every second stop. Thus, 40 stems and 40 pods were rated. Incidence (percent of stems infected) was recorded for blackleg and Sclerotinia. Severity (percent of pod area affected) was recorded for black spot. Results are shown below. Please note that there were some errors in the previous survey report.

County

Blackleg Incidence

Sclerotinia Incidence

Black Spot Severity

Benson

0.3%

6.9%

0.3%

Cavalier

0.8%

18.8%

0.5%

Ramsey

0.8%

9.5%

0.3%

Rolette

0.3%

31.0%

1.3%

Stuttsman

0.3%

14.0%

0.1%

Towner

9.3%

20.5%

1.0%

Wells

3.0%

11.8%

0.5%

N. Dakota

2.0%

16.3%

0.6%

    The blackleg incidence in Wells County was due to a field with 28% blackleg. However, the blackleg lesions appeared to be superficial, and not girdling. The lesions were not causing premature dying of the plant, and so it appears that this was the low virulence strain of blackleg, which is not serious. The blackleg incidence in Towner County was due to a field with 82% incidence. The blackleg in this field appeared to be caused by the severe strain, which causes girdling of the stems, and can cause premature dying and severe losses.

    Surveys of Bottineau, Renville and Ward Counties are being conducted by Kent McKay. A preliminary report can be found in his article in this issue of the Crop and Pest Report.

    The preliminary data indicate that Sclerotinia incidence was much higher in Rolette and Towner Counties than it was last year, and that the overall Sclerotinia incidence was higher than last year. Blackleg incidence was slightly higher than last year, and Alternaria severity was also slightly higher. These data may change somewhat when the final figures are compiled.

 

CANOLA FUNGICIDE TRIAL AT NEWBERG

    Kent McKay’s trial at Newberg had heavy Sclerotinia infection, with over 50% of the untreated plants infected. Quadris was applied at 6.8, 9.6 and 13.7 fl oz/A. All the pre-bloom treatments were not significantly better than the untreated check. All three treatments applied at 20% bloom had significantly less Sclerotinia than the untreated check, and were not significantly different than Benlate at 0.9 lb/A. Note that the section 18 rate for Quadris in 1997 was 15 fl oz/A, at a cost of $32/A. The 6.8 fl oz rate at 20% bloom provided nearly as good Sclerotinia control as Benlate (no statistically significant difference); this rate could be cost effective and competitive with the cost of Benlate. A similar trial conducted by Bryan Hanson at Langdon had a low incidence of Sclerotinia in spite of the trial being misted daily (it was located next to the wheat scab nursery).

 

DETERMINE SCLEROTINIA LEVELS NOW

    It is important for producers to get an estimate of the amount of Sclerotinia (white mold) in susceptible crops and to keep records of these levels. This will help determine future crop rotations and avoid fields with high levels of Sclerotinia. Since Sclerotinia spores can blow in from nearby fields, avoiding badly infested fields is not a guarantee that Sclerotinia will be avoided, but it is a start. It is especially important to avoid planting sunflower into badly infested fields, since Sclerotinia wilt (infection through the roots) can occur at almost any soil moisture capable of supporting growth of sunflower. In contrast, Sclerotinia head rot in sunflower and infection in dry bean, canola, crambe, lentil, soybean, and field pea occurs from infection by airborne Sclerotinia spores which infect dead or dying flowers in wet weather.

 

PRELIMINARY RESULTS OF 1997 DRY BEAN GROWER SURVEY   

    Lenny Luecke completed a summary of the results of the 1997 dry bean grower survey last week. This survey was not mailed out as previous surveys, but was distributed at Northarvest Bean Day in February of this year. There were 206 useable forms returned, or about 30% of the forms returned in the mail survey in 1996, but at a fraction of the cost. The respondents planted 92,437 acres, or about 40% of the acres planted by respondents in the 1996 mail survey.

  Varieties. Montcalm dark red kidney was the most commonly planted variety in Minnesota (MN), planted on 16% of respondents’ acres, followed by Norstar navy on 13% and Topaz pinto on 10%. Norstar navy was the most commonly planted variety in North Dakota (ND), planted on 14% of respondents’ acres, followed by Othello pinto on 10%.

    Worst Production Problem. Weather was the worst production problem on 46% of MN and 30% of ND respondents’ acres, followed by disease on 18% of MN and 19% of ND respondents’ acres.

    Worst Disease Problem. White mold was the worst disease problem on 63% of MN and 62% of ND respondents’ acres. Root rot was the worst disease problem on 10% of MN respondents’ acres. Rust was the worst disease problem on 7% of ND respondents’ acres.

    Fungicide Use. The table below indicates the percent of respondents’ acres treated with various fungicides. Separate entries are given for Benlate and Topsin M applied broadcast (broad) versus those applied as a directed spray (band).

Fungicide

% Acres Treated

Minnesota

North Dakota

Bravo

0.7

2.0

Benlate Broad

20.2

8.3

Benlate Band

7.6

2.0

Tilt

6.4

7.2

Topsin Broad

19.5

9.6

Topsin Band

4.9

7.7

    The most commonly applied fungicides were the white mold fungicides Benlate and Topsin M; these fungicides were applied on 52% of MN and 28% of ND respondents’ acres. Broadcast application was more common than a directed spray (band).

    Worst Weed. Redroot pigweed was the worst weed on 28% of MN respondents’ acres, followed by foxtail on 18%, nightshade on 14%, ragweed on 11% and lambsquarters on 10%. Nightshade was the worst weed on 19% of ND respondents’ acres, followed by foxtail, Canada thistle and kochia, each on 15%.

    Herbicide Use. Post-emergence Basagran was the most commonly used herbicide, with 52% of MN and 48% of ND respondents’ acres treated. Pre-plant spring applied trifluralin was the second most commonly used herbicide by MN respondents, applied on 30% of their acres, followed by fall-applied Sonalan on 26%, past applied Assure II on 22%, spring-applied Lasso on 14% and pre-plant Prowl on 13%. Pre-plant spring applied Sonalan was the second most commonly used herbicide by ND respondents, applied on 34% of their acres, followed by pre-plant spring applied trifluralin on 28%, post-applied Pursuit on 26%, fall-applied Sonalan on 19%, Assure II on 18% and Poast on 10%.

    Worst Insect. Grasshoppers were the worst insect on 14% of MN and 15% of ND respondents’ acres, followed by leafhoppers on 10% of MN and 8% of ND respondents’ acres.

 

CRISIS EXEMPTION FOR CHLORINE DIOXIDE ON STORED POTATOES

    A crisis exemption was declared for the use of chlorine dioxide on stored potatoes in North Dakota effective August 19 for control of late blight and secondary soft rot on stored potatoes in North Dakota. The product is approved for use up to 200 ppm and will be distributed by Ostlund Chemical Co. in Fargo. The crisis exemption is effective until September 3, but it is anticipated that EPA will grant a specific exemption effective until June 30, 1999.

Art Lamey
Extension Plant Pathologist


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