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ISSUE 15  AUGUST 12, 1999

 

CANOLA DISEASE SURVEY BEGINS

    The canola disease survey is beginning. Survey will be done in fields when the crop is in the swath.
Emphasis will be on the counties with major acreages in 1998: Cavalier, Bottineau, Towner, Ramsey,
Benson, Rolette, Stutsman, and Wells counties in North Dakota; and Roseau, Marshall and Kittson
counties in Minnesota. Kent McKay, Janet Knodel and crop surveyor Brittany Sund will survey the
northwestern part of North Dakota. Greg Endres and crop surveyor Jerry Schneider will survey
counties around the Carrington REC, and Art Lamey and crop surveyor Jerry Ries will survey the
northern tier of counties in North Dakota. The Minnesota survey will be done by Dr. Dick Meronuck,
extension plant pathologist, University of Minnesota, Zach Fore, Minnesota Extension Area Specialist,
along with Art Lamey and Jerry Ries.

    The survey will determine the incidence and distribution of Sclerotinia stem rot and blackleg and the
severity of Alternaria black spot. In addition, some canola growers have been contacted in specific
areas and their cropping patterns determined. We will attempt to determine if there is any relationship
between crop rotations, weather patterns and disease.

    In east Polk County Minnesota and in Stutsman County, North Dakota, very little blackleg was
found last week and Sclerotinia incidence was moderately high in only one field in each county. Aster
yellows was present in almost every field in both counties. It is difficult to determine the incidence of
aster yellows in swathed fields, but it may have been as high as several percent in some fields.

 

ASTER YELLOWS IN CANOLA

    Aster yellows is common in canola this year. It has not been observed in previous surveys, so
apparently was not common. Affected plants have a cluster of green leaf-like flowers near the tip of
the raceme. In some cases, the cluster has shortened internodes, resulting in a witches’ broom at
the tip of the raceme. Some of the upper pods form into short, flat, broadened bladder-like structures.
Yield of affected plants will be reduced, but the overall impact on yield will not be great unless the
percent of infected plants exceeds 10%. Although prevalent and striking, I doubt if the incidence is
that high in most fields observed to date.

    Aster yellows is a mycoplasma-like organism that is transmitted by the aster leafhopper. The
leafhopper blows in each year from areas to the south of us. Apparently we had more leafhoppers
than usual this year, or a higher percentage were carrying the aster yellows organism.

 

RHIZOMANIA ON SUGARBEET

    Dr. Al Cattanach, General Agronomist for American Crystal Sugar Company, reports a number of
fields in Cass and Traill counties, in North Dakota and in Clay and Norman counties of Minnesota
with symptoms typical of rhizomania. Affected areas may be near low spots or waterways. The foliage
will have a fluorescent yellow appearance, and some of the petioles will be elongated and the leaves
narrower than normal. The roots will have a hairy appearance. The fluorescent foliage is b est seen on
cloudy days or early or late in the day when light intensity is reduced.

    At present, there is no action that can be taken except to keep track of locations with suspected
rhizomania. Rhizomania-resistant varieties that are suitable for our area should be available within a
few years. This probably will be the long-term solution to rhizomania problems.

Art Lamey
Extension Plant Pathologist
alamey@ndsuext.nodak.edu

 

WHEAT AND BARLEY FUNGICIDE TRIALS, 1999

    A large number of fungicide trials on spring wheat, durum wheat, and barley are again being
done by NDSU in 1999. Locations of the main trials include Fargo, Carrington, Langdon, and
Minot, with a few off-station trials, as well. Included in these trials are evaluations of product
efficacy against head scab and the leaf diseases, plus evaluations of application techniques. Most
trials have been evaluated, and some, but not all, harvested. Once the data has been analyzed, we
should have some very good information on product performance in 1999 and how some new
application techniques worked for head coverage and disease control.

    A uniform fungicide trial was established at Fargo, Carrington REC, Minot REC, and Langdon
REC. In some locations, the trial was not only on hard red spring wheat, but also durum and or
barley. Nine fungicide treatments were evaluated against the untreated check. The nine treatments
included a high rate of Folicur, Benlate + Mancozeb, Penncozeb, two timings of a BASF experimental,
two rates of a Novartis experimental, and two rates of Quadris. This trial also was done on wheat in
13 other states across the country that have had a history of scab. Some of these states had very little
disease this year because of drought, others should have good scab and leaf disease data. All of the
data from the Uniform Trials and the 14 state effort will be summarized and made available this fall.

    In addition to the Uniform Fungicide Trial, ND researchers looked at some new experimental
products in cooperation with several crop protection companies this year. In Fargo we had 10 trials
in with cooperation with private industry. We also have further evaluated application techniques at
Langdon and Fargo. Included in the 1999 evaluations are an experimental Spray Air system provided
by Spray Air to John Lukach at the Langdon REC, and a modified air assist sprayer built here at Fargo
by Agricultural Engineering and Biosystems Dept. and Plant Pathology Dept. personnel. We also had
two aerial application trials in Cass county in 1999.

    Although disease ratings and harvest data are not yet complete, preliminary results indicate that
most fungicides did a very good job against the leaf and head diseases in 1999, depending on rate and
application timing, and that certain application procedures provided better coverage and disease control.
Look for summaries of these results later this fall.

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

 

PLANT DIAGNOSTIC LAB REPORT

    Two weeks ago, I reported that false black chaff was observed on the wheat variety McKenzie.
Since that time, black chaff, the bacterial disease has been confirmed on McKenzie, and on several
other varieties of wheat as well. Both Drs. Marcia McMullen and Mike Peel stated that they have
observed a higher incidence of this disease than in recent years.

    The organism that causes black chaff is Xanthomonas campestris pv. translucens, a bacterium
that can survive in crop residue and seed. It is spread in the field by splashing rain and sprinkler irrigation
water. Wheat, barley, and oats are all susceptible to infection by this pathogen.

    Symptoms to look for with black chaff include a purplish-black discoloration of the glumes, in patches
or streaks. This dark discoloration may also be visible on the awns, in a striped pattern, giving a barber-
pole appearance to the awn. It is also typical to see striped lesions on the peduncle of the plant. This is
not a typical symptom of melanism and can be one way to differentiate between false black chaff and
the bacterial infection, black chaff.

    Crop rotations, which are a good general disease management practice, to non-cereals can help reduce
disease incidence. Since this disease can also be seed-borne, it is not be wise to use seed from an infected
crop. Under dryland conditions, damage to the grain is usually negligible if infection occurs late in the season.
However, under sprinkler irrigation, yield losses have been reported to be severe.

    Last week, there was a list of the diagnoses from the previous week in the lab. One of those listed was
Accent injury to corn. Normally, we don’t try to visually diagnose injury caused by a specific product,
so this was an exception. The reason for that was that the client stated that Accent had been applied, but
the diagnosis was really of a misapplication of the herbicide. The chemical was applied outside the window
of application, so the diagnosis really should have stated that the injury was the result of a late application
of Accent.

Cheryl Ruby
Plant Diagnostician
diaglab@ndsuext.nodak.edu


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