ISSUE 8   June 28, 2007

NDSU IPM CROP SURVEY - June 18-22

Wheat:

The NDSU field scouts examined 119 wheat fields last week across all parts of the state. The wheat surveyed was in all stages, from 2-leaf in the far north to post-flowering stages in some winter wheat fields. Many spring wheat fields were in the boot to heading stages.

Tan spot leaf infection was again the most common disease observed, found in 92% of the fields surveyed, with moderate to high severities observed on flag leaves of winter wheat, but severities of 1-5% were recorded on leaves of most spring wheat fields, including those not yet in the flag leaf stage. Ten percent of the fields were reported as showing symptoms of Septoria (Stagonospora) leaf blotch, a fungal disease frequently seen later in the season as temperatures increase. The speckled fruiting bodies of the Septoria fungus were evident with a hand lens in lesions in some spring wheat cultivars at the Carrington Research Extension Center. The symptoms of Septoria may easily be confused with tan spot if the fruiting bodies are not evident, but generally the lesions have a smaller yellow halo, and the centers of the lesions get a more greyish appearance, as well (see figure).

Septoria leaf blotch
Septoria leaf blotch symptoms on spring wheat leaves

Leaf rust was observed in 36.1% of the fields surveyed, about twice as many as the previous week. However, average severity of leaf rust remained low in spring wheat (1-8%).

One head in a winter wheat field in the southeast was observed with Fusarium head blight (scab) symptoms. Incidence in winter wheat may become more obvious, generally about 3 weeks after flowering.

Grain aphids were commonly observed in the southeast, south central, northeast and southwest counties for the week of June 18-22, an increase in numbers and distribution from the previous week.

Barley: The NDSU field scouts observed 50 barley fields during the week of June 18-22. These barley fields still had a wide range of growth stages, from the 2-leaf stage to heading in other fields. The most common disease reported for these barley fields was the same as the previous week, spot blotch, with a few showing net blotch and bacterial blight, as well. Fungal leaf spot severity ranged from 1% to 25%. Only one field showed very low levels of barley leaf rust.

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

 

NEW RACE OF DRY ANTHRACNOSE IN MANITOBA

On Monday, I spoke to dry bean pathologist Dr. Robert Conner at the Agri-Food Canada research station in Morden, Manitoba. He informed me that a new race of the pathogen causing anthracnose of dry edible beans was found in Manitoba. A good article about this find appears in the most recent issue of the Manitoba Pulse Growers Association publication Pulse Beat (spring/summer 2007 : Issue 51).

Anthracnose has been observed in North Dakota for years, but only race 73 has been identified in the state. The new race (race 105) was isolated on the cultivar Envoy, which is resistant to race 73. Although race 105 has not been found in North Dakota, other diseases have spread freely between Manitoba and North Dakota. With all the rainfall this spring and early summer, conditions are favorable for disease development and movement.

Anthracnose can cause disease on all above ground parts of bean plants. Leaf symptoms are small elongated lesions on petioles and follow the vein patterns of a leaf. On pods, anthracnose produces small sunken cankers with a dark brown border. Dark brown lesions are observed on seed when pods are infected in their early stages of development.

Dry antrhacnose            Dry antrhacnose            Dry anthracnose on dry beans

I am interested in collecting anthracnose samples on dry beans, particularly those found on resistant varieties (Envoy or others). Infection on a resistant variety could indicate a new race is causing the disease. Please send any suspicious anthracnose samples to:

NDSU Plant Diagnostic Lab
Department of Plant Pathology
306 Walster Hall; PO Box 5012
Fargo, ND 58105-5012

Race identification takes time, and will not likely be done until fall or winter. However, samples collected this year can provide valuable information for next year’s crop. Thank you for helping us keep on top of the situation.

 

GROWING DEGREE DAYS AND THE SCLEROTINIA RISK MAP

When accessing the Sclerotinia Risk Map website, two other maps are presented; a top zone soil moisture map, and a growing degree-days map. Recently, there have been questions regarding the accuracy of the growing degree map. The growing degree map estimates the growth stage of Canola in a defined area, but it is based on a regionally-averaged planting time and subsequent growing degree days. Each field is different, and in many cases what the map says is incorrect for an individual field. The important thing to remember is that Canola is susceptible in the flowering stage. When your field is flowering the Risk Map can be applied to your field, otherwise, it is irrelevant. Once your field flowers, NDSU canola pathologist Dr. Luis del Rio suggests looking at the current risk map and the two maps prior. These three most recent maps have shown to have the highest correlation to disease development.

If your field is not flowering the risk map is irrelevant to your field. The sclerotinia risk map is available at

http://www.ag.ndsu.edu/sclerotinia or http://www.northerncanola.com/maps/index.asp

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


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