ISSUE 11   July 22, 2010

NEW PLANT PATHOLOGIST AT CARRINGTON RESEARCH EXTENSION CENTER

On June 1, Michael Wunsch joined NDSU as the plant pathologist at the Carrington Research Extension Center.  He has a 70% research and 30% extension appointment, and he will be working with the breadth of crops grown in North Dakota. 


Michael Wunsch
 

Michael’s research activities in Carrington are focused on disease management.  He will be assuming responsibility for field trials assessing varietal disease resistance and fungicide efficacy and timing, and he will collaborate with agronomists at the station in cropping systems research.  Michael also has interests in disease etiology, pathogen epidemiology, and pathogen diagnostics, and he will conduct research in these and other areas of plant pathology as needed.  His extension responsibilities will be focused on the diseases impacting crops grown across North Dakota. 

Michael obtained his Ph.D. in May 2010 from Cornell University in Ithaca, NY.  At Cornell, he investigated the etiology of brown root rot of alfalfa and Fusarium wilt of birdsfoot trefoil, the distribution and host range of the causal pathogens Fusarium oxysporum f. sp. loti and Phoma sclerotioides, and the epidemiology of P. sclerotioides.  He studied under the guidance of Gary Bergstrom, the New York state extension field crops pathologist.  Michael received a B.S. in biology and a B.A. in economics from the University of Missouri-Columbia, and he served with the U.S. Peace Corps in Honduras prior to commencing his graduate studies.  Michael is originally from Montana.

 

NDSU IPM SURVEY RESULTS, JULY 16

      Wheat:  NDSU IPM scouts looked at 61 wheat fields the past week, with the average growth stage of these crops at kernel watery ripe.  However, in the southeast and south central regions, most of the crop is in soft dough stage, while in the north central and northwest areas, the crop ranges from tillering stage to soft dough, so less mature crop in the west and north central regions.   Average tan spot severity has crept up a bit, to an average of 5% on top leaves.  Septoria leaf blotch also was observed, in 18% of the fields.  The scouts did not report any observations in commercial wheat fields of leaf rust or stripe rust this past week.  Five of the 61 wheat fields were observed with symptoms of Fusarium head blight (scab), with an average severity of 5.0%.   In the north central region, a lot of wheat stem maggot also is being observed.  Wheat stem maggot causes a bleaching of the head and stem, down to the first node, while scabby heads generally have partial head infection, or if complete head infection, the stem right below the infected head often has a purple color (see figures). 


Scab with discolored stem.


Wheat stem maggot.

Fourteen fields were observed with wheat streak mosaic symptoms, primarily in the north central and western regions, and two with barley yellow dwarf symptoms. Bacterial leaf blight symptoms were also observed in 10 fields, primarily in less mature fields of the north central and western regions. 

Barley: Seven barley fields were surveyed and the average growth stage in these surveyed fields was kernel watery ripe.  No observations of scab were made this past week, and net blotch and Septoria were the fungal leaf spots observed.

Marcia McMullen
NDSU Extension Plant Pathologist
marcia.mcmullen@ndsu.edu

 

SUNFLOWER RUST UPDATE

In the last two weeks, approximately 60-70 fields have been scouted for rust in North Dakota.  Only 10-15% of them have had some rust, and with two exceptions, all fields have low severity and disease was limited to lower leaves.  The majority of fields where rust was found were near the Canadian border; significantly less was observed in the southern part of the state.

It is important to scout for rust.  The pathogen can be distinguished from other diseases by the dusty cinnamon-brown pustules (Figure 1).   


Figure 1.
  Sunflower rust pustules. 

Fungicide trials in the last two years suggest a fungicide application is most effective when the severity on the upper four fully-expended leaves is approximately 1-3% (Figure 2).  In our trials, a single application applied in this severity range during bloom (R5’s) managed the disease very well.  In fields where severe rust is observed in vegetative stages, two applications could be necessary.  However, this situation appears to be a rare and localized event, and will depend on a prolonged favorable environment (frequent heavy dews, moderate to warm temps). 


Figure 2.
Computer generated image representing
1% (left) and 2% (right) rust severity on sunflower leaf.

Headline, Quadris, and tebuconazole products (Folicur and other generics) are labeled for use on sunflower.  More information about rust management, plus research trial data, and management presentations can be found at the National Sunflower Association Website, www.sunflowernsa.com.

 

SUNFLOWER DOWNY MILDEW UPDATE

Dr. Tom Gulya is mid-way through a survey for sunflower downy mildew in North Dakota.  To date, he surveyed 63 fields, and has observed downy mildew in 60-70% of them.  However, only three fields with economically-destructive levels of downy mildew were observed; all of them south of Bismarck.  Dr. Gulya will in continuing his survey this week into the Devils Lake area and Northeastern North Dakota. 

Dr. Gulya’s effort to observe and obtain samples of downy mildew infected sunflowers is important for future disease management.  The pathogen race(s) will be determined and used to help future resistance breeding efforts.  If you are willing to help and have a field with severe downy mildew, particularly if a downy mildew resistant hybrid was planted, please contact myself or Tom Gulya (thomas.gulya@ars.usda.gov) for sample collection/submission.  The race information will be provided back to you after the greenhouse tests this fall/winter.  Typical symptoms of Downy mildew include plant stunting (Figure 3), rigid leaves, chlorosis on leaves which appears to be radiating from the petiole, and white fluffy growth on the undersides of the leaves.  More information and photos of symptoms can be found in NDSU extension publication PP-1402 at www.ag.ndsu.edu/pubs/plantsci/rowcrops/pp1402.pdf.

 

SCOUT FOR COMMON BEAN RUST

Since a new race of the common bean rust pathogen was identified two years ago, bean rust has been a looming threat to our dry bean crops.  Although I have not heard of bean rust appearing yet this year, it is important to scout for the disease.  Bean rust likes heavy dews and moderate – warm temperatures; conditions we that have had recently.

Look for pustules in the middle to lower part of the bean canopy.  Pustules are raised cinnamon-brown bumps.  Spores can easily be rubbed off leaving a streak on your thumb (Figure 3).  The most common misidentification of the disease is soil-splash on the undersides of the leaves after a rainstorm.  However, when rust pustules are rubbed, the pustules will remain as a cream-colored lesion, soil will not.  Bean rust is most likely to be found first where dew periods are the longest; next to tree rows is a good place to look.   


Figure 3.
Bean rust pustules.

If bean rust is found, please contact your county agent.  Together we can put out alerts if needed, and make recommendations that fit the situation.  Fungicide data from last year’s trials indicate that we can manage this disease with fungicides, as long as it is detected early.

 

PULSE CROP DISEASE SURVEY

Dr. Rubella Goswami’s research team is currently scouting for, and sampling pulse crops for disease.  Last week they sampled 27 pea, lentil, and chickpea fields in southern ND.  This week they are sampling/surveying the northern half of the state.  Samples collected during this trip will be used to assess pathogen incidence and severity in each crop, to monitor for the development of fungicide resistance, possibly screen for genetic resistance in germplasm in the future, and help us make the most appropriate disease management strategies.

To date, there have been limited surprises.  Ascochyta and root rots appear to be the most common diseases.  Results of most tests (fungicide resistance monitoring for example), will be done during the fall/winter seasons and made available as the information is generated.

Sam Markell
Extension Plant Pathologist
samuel.markell@ndsu.edu


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