ISSUE 4 May 27, 1999SMALL GRAIN DISEASE UPDATE
About 50% of the spring wheat crop was planted by May 23, 1999,
according to the latest ND Crop
Weather Report released by the North Dakota Agricultural Statistics Service. Some producers who have
observed tan spot on their early planted wheat may be applying early season fungicides with their herbicides.
Others are just trying to get the crop in. The later seeded crop MAY face an increased risk of exposure to
leaf rust and to grain aphids carrying barley yellow dwarf virus, as mentioned in previous Crop and Pest
reports. However, a lot can happen between now and later grain stages that could affect disease
development. Weather conditions here will influence the development of major leaf spot and head diseases,
with all of them being favored by wet weather and high humidities as the crop develops. Weather patterns
in the next few weeks in states to our south will influence development and movement of leaf rust and grain
aphids. The USDA Cereal Rust Bulletin #4, May 25th edition, reports that the northward development of
leaf rust has been slow into the Great Plains because of the cooler than normal weather and moist
conditions which kept the spores within the crop canopy. Currently, Nebraska is reporting very few
disease problems in their winter wheat, while Kansas is reporting only light levels of leaf rust. The most
severe disease in Kansas winter wheat appears to be barley yellow dwarf virus, according to their Plant
Disease Survey Report #3, dated May 20.
SMALL GRAIN FUNGICIDE RESEARCH
This past winter a semi-permanent greenhouse was built on the
NDSU campus and was dedicated to housing
experiments on fungicide application techniques for improving grain head coverage and for reducing Fusarium
head blight (head scab) severities. Over 40 experiments were run to evaluate nozzle types, droplet size,
sprayer pressure, water volume, and adjuvants. The work was a continuation of work done in the field in
1998. A summary report of this greenhouse research will be provided soon, so that growers will have the
option of adjusting their spray techniques to improve fungicide coverage for scab control.
Considerable fungicide efficacy and application technique studies
also will be done in the field this summer,
on hard red spring wheat, durum, and barley. Some new and promising experimental compounds for control
of head scab as well as leaf diseases will be tested at a number of Research/Extension Center locations
throughout the state. ND also will be cooperating in a 14 state Uniform Fungicide Trial to evaluate a standard
set of 10 treatments for efficacy in controlling Fusarium head blight (head scab). In addition, further work will
be done on application techniques, including looking at spray variables with an air assist sprayer, plus
examining adjuvants and other spray variables.
Extension Plant Pathologist/IPM Coordinator
KODIAK SEED TREATMENT ON KIDNEY BEANS
Some producers have inquired about using KODIAK seed treatment on
kidney beans. Kodiak is a
biological seed treatment containing GBO3 strain of Bacillus subtilis , manufactured by Gustafson. The
label indicates that the bacteria "colonize the developing root system, suppressing disease organisms such
as Fusarium, Rhizoctonia, Alternaria and Aspergillus. When used with a chemical seed treatment, the
combination of chemicals and KODIAK provides protection to the root for a much longer time than with
chemicals alone. As the root system develops, the bacteria grow with the roots extending the protection
throughout the growing season. As a result of this biological protection, a vigorous root system is established
by the plant, which often results in more uniform stands and greater yields. In addition, KODIAK has been
shown to increase the amount of nodulation by nitrogen-fixing bacteria when used on many legumes.
This improvement in nodulation is a result of a healthier root system allowing more sites for nodules to
form from naturally -occuring soilborne nitrogen-fixing bacteria."
This may sound like product-pushing hype, but seeing is believing!
Research in the Plant Pathology
Department at the University of Minnesota by Consuelo Estevez deJensen, Dr. Dick Meronuck and Dr.
Jim Percich confirmed most claims. They observed that KODIAK-treated kidney bean seed had less
Fusarium root rot and Fusarium yellows (a vascular wilt caused by a different species of Fusarium than
the root rot). Rhizoctonia root rot was suppressed slightly in a single preliminary greenhouse trial. Nodulation
and root growth was improved.
Last summer Green Valley Bean Company helped several kidney bean
growers in the Park Rapids, MN
area to set up KODIAK treated and untreated halves of center pivot circles. There appeared to be noticeably
less Fusarium root rot in the KODIAK treated halves of most trials visited. Root development and nodulation
was noticeably better in the KODIAK treated halves.
KODIAK may be applied to the seed along with other standard seed treatment products.
USE OF QUADRIS FOR CONTROL OF BLACKLEG IN CANOLA
Although blackleg has not been a serious problem in most North
Dakota canola fields in recent years,
it has been a serious problem in a few fields planted to susceptible Argentine cultivars. In previous years,
it was a common problem on Polish canola, grown in north central North Dakota. With the advancing season,
there may be some producers thinking of switching to a Polish cultivar. All Polish cultivars currently available
are susceptible to blackleg.
Quadris fungicide, recently registered on canola, is registered for
blackleg control. It is to be applied at
6.2 fl oz/A when the crop is in the 2-4 leaf stage. Data from trials in western Canada have shown a reduction
in the percent plants girdled, with the percent girdled reduced to about half when disease was severe.
Under conditions of severe disease, yield increases of 15-20% were documented in some trials. The use of
Bond as an adjuvant provided only marginal improvements over Quadris alone.
Extension Plant Pathologist
PLANT DIAGNOSTIC LAB REPORT
The samples submitted to the lab this week are predominantly trees.
Most of the problems with these
trees are due to environmental causes such as winter injury, high salts in the soil, and saturated soils. Ash
anthracnose has also been a big news item this week (see last weeks pest report for a detailed article). The
other cause of injury symptoms on trees this week is herbicide damage. Homeowners and growers are both
spraying now to control weeds in yards, gardens, and fields. When good care in herbicide application is not
exercised, injury can occur to trees through drift or direct application on the trees.
Trees are amazingly compensatory and may eventually recover from
herbicide injury. But if a herbicide is
applied in a high enough concentration, or if the injury is repeated several years in a row, trees may be killed.
Even if the damage is not severe enough to kill the tree, the stress on the tree from herbicide injury may reduce
the vigor and/or the life span of the tree.
Some symptoms of herbicide injury are droplet-type spots that appear
like a contact burn on leaves or a
general yellowing of tissue that has been sprayed. Phenoxy herbicides may cause the typical symptoms of petiole
twisting, leaf cupping, leaf elongation, and parallel venation. It is important to recognize that any of these symptoms
may also be the result of other biotic or abiotic factors so the context of the tree in question is critical. If a
herbicide injury is suspected, good documentation will be important. Take pictures of the injury symptoms,
note dates and check wind speed and direction for that date, try to ascertain what type of herbicide may have
drifted or been applied to the tree, and/or contact a forestry consultant for a site visit.
NEW SERVICE OFFERED THROUGH THE PLANT DIAGNOSTIC LAB
Visual diagnosis is still common in suspected herbicide
injury, but, in conjunction with Dr. Alan Dexters
lab, we can now offer Roundup (glyphosate) testing on plant material. Samples should be sent to the diagnostic
lab, and the fee for this test will be $150.00/sample. If possible, submit a "healthy" (non injured) sample and a
sample from the tree or part of the tree showing symptoms. As with all samples, also send a name, address, and
phone number for the contact person, and a complete description of the location of the tree and surroundings.