ISSUE 9   July 5, 2007

WHEAT DISEASE FORECASTING

The NDSU wheat disease forecasting model

indicated on July 3rd that flowering wheat is still at risk for Fusarium head blight in northern tier counties in ND, especially if cultivars being grown are susceptible or moderately susceptible and still approaching or in the flowering stage. The Penn State FHB forecasting web site also indicated risk along the eastern-northern tier counties of ND, but indicated that the risk will go down as the weekend approaches, with the high temperatures predicted. Much of the wheat in the southern half of ND has finished flowering.

Wheat leaf disease infection risk has gone down in most areas of ND, because of recent high temperatures and drier conditions, but leaf rust in susceptible cultivars may continue to develop, as the leaf rust fungus only requires 6 hours of dew for infection. Crops past flowering but showing flag leaf disease are also past the window of fungicide application.

NDSU Disease Forecasting site:

http://www.ag.ndsu.nodak.edu/cropdisease/cropdisease.htm

Penn State Scab Forecasting site:

http://www.wheatscab.psu.edu

 

PRELIMINARY RESULTS OF FUNGICIDE EVALUATION IN WINTER WHEAT

Evaluations of disease levels and fungicide treatment were done on winter wheat cultivars at Lisbon, ND on July 2, 2007. Leaf disease was very severe in the untreated plots of many cultivars of winter wheat at this site, with many flag leaves consumed completely by a combination of leaf rust and Septoria leaf blotch, plus some bacterial stripe in a few cultivars.

The fungicide treatment in this trial was a single flowering application of 3 fl oz of Proline + 3 fl oz of Folicur. This mixture was very effective in controlling fungal leaf disease. Three weeks after treatment, there was still 100% control of leaf rust, and between 80-90% control of Septoria in treated plots. The bacterial leaf infection present on some cultivars was not controlled with fungicides.

Fusarium head blight also was reduced by fungicide treatment, with preliminary calculations indicating from 60-80% reduction in field severity on susceptible cultivars. Similar evaluations will be made at other locations of winter wheat cultivars, and also on spring wheat cultivars.

Marcia McMullen
Ext. Plant Pathologist
marcia.mcmullen@ndsu.edu

 

ASCOCHYTA BLIGHT IN PEAS

Ascochyta blight is a fungal disease that can infect peas. It was a wide spread problem in 2005. Symptoms of ascochyta blight appear as either tan to brown or purple in color, depending on the pathogen. Pycnidia, which are black fruiting bodies of the fungus, may be found spread throughout the center of the lesions. Wet conditions promote the disease. All pea varieties are susceptible to ascochyta blight, but some may be more susceptible than others. Headline and Quadris are registered for control. Fungicide trials conducted in 2005 in Leeds and Mohall showed excellent returns by applying fungicides at the 50% bloom stage. The optimum stage for applying fungicides to peas is between 30 to 50% bloom. At 50% bloom, there will be ˝ to 1 inch pods present. Fungicides applied on the developing pods will reduce pod lesions later in the growing season.

Pea Fungicide Trials Results 2005 (McKay, Novak NCREC, Minot)

Location

Fungicide

Yield (bu/A)

Leeds

Untreated

37

Quadris 6.2 fl oz/A

44

Headline 6 fl oz/A

43

Mohall

Untreated

40

Quadris 6.2 fl oz/A

43

Headline 6 fl oz/A

46

 

DISEASE CONCERNS IN LENTILS

Fungal diseases, ascochyta blight and anthracnose, can be devastating diseases in lentils under wet, humid conditions. It is very important to monitor lentils for both diseases now as they begin to bloom.

Ascochyta blight is a fungal disease caused by a specific strain of ascochyta that infects only lentil. It is a different species from the fungus/ascochyta that infects chickpea or dry pea. There are lentil varieties more tolerant to ascochyta; however they are not resistant and all varieties need to be monitored for disease. Ascochyta lesions are tan or grey with dark black/purple margins and tiny black fruiting bodies located in the center of the lesion. Lesions can be found on leaves, stems and/or pods.

Athracnose is a severe disease in lentil when present. Lesions are grey to cream-colored on leaves and tan or dark brown on the stems. The disease usually infects in patches within a field and the infected areas prematurely ripen and turn dark brown.

Ascochyta and anthracnose can be controlled by timely applications of Headline or Quadris fungicides. It is very important to apply these fungicides before the onset of disease. For best results, the timing of a single application is usually at early flower, 30 to 50% bloom. If the fungicide application is applied at 50% bloom there will developing pods present, which will reduce pod lesions and seed infection later in the growing season.

The following table lists the fungicide results of a single application, applied between 30-50% bloom stage, of Headline and Quadris fungicides at the North Central Research Extension Center, Minot, ND.

Lentil Fungicide Trials Results (McKay, Novak, Michels NCREC, Minot)

Year

Fungicide Treatment

Yield (lb/A)

2002

Untreated

1526

Headline 6 fl oz/A

1913

2003

Untreated

1489

Headline 6 fl oz/A

1467

2005

Untreated

1030

Quadris 6.2 fl oz/A

1263

Headline 6 fl oz/A

1419

2006

Untreated

1571

Quadris 6.2 fl oz/A

2071

Headline 6 fl oz/A

1960

Kent McKay
Area Extension Agronomist
North Central Research Extension Center, Minot
kent.mckay@ndsu.edu

 

SOYBEAN RUST UPDATE

Since the first report of soybean rust this year (May 8, Iberia Parish, Louisiana) the disease has been found in Florida, Texas, additional sites in Louisiana, and as of June 26, Alabama. Most findings are along the coast, where the disease is able to overwinter. The disease was found in these regions last year, but approximately one month later in the season.

A national effort to monitor the spread of soybean rust is underway in the United States. Plant pathologists have established ‘sentinel plots’, which are soybean fields scouted for soybean rust on a weekly or biweekly basis. In North Dakota, 20 sentinel plots are established throughout the eastern half of the state, and scouting began last week. Updates from the national scouting effort are available at http://www.dtnsoybeanrustcenter.com/. Soybean rust in southern states does not pose an imminent threat to soybeans in North Dakota, but it is best to be aware that the disease is active to our south. The disease has a long way to spread before it would reach us, and numerous states in the Great Plains would report disease before it could threaten North Dakota. In the event that it spread into the Great Plains, we will keep growers informed on a timely basis. In the event that soybean rust appeared in North Dakota, numerous fungicides can be used to control the disease.

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


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