Posts Tagged ‘barley scald’

Agronomic Crop Disease Update – May 13, 2011

Thursday, May 12th, 2011

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Barley
Powdery mildew on ‘Thoroughbred’ is the most common disease at the present time. Fields with the top two leaves with mildew will have some yield reduction. After looking at the variety trials in Sussex County on Tuesday I could also find small amounts of leaf rust, barley scald and the spot form of net blotch. None of these should impact yield.

Wheat
Wheat is looking very good at the present time. There is very little disease present. A few unsprayed varieties have some powdery mildew that is confined to the lower leaves and leaf sheaths. A small amount of leaf rust was also spotted on one unsprayed variety on the lower leaves. Most of the wheat that I saw has flowered and with the dry weather in most of the southern parts of the state, it looks like head scab should not be a problem. In the northern areas of the state if we get showers this weekend we may have some opportunity for infection if wheat is flowering.

Barley scald

Soybeans and Soybean Cyst Nematode
It is still not too late to check for soybean cyst nematode especially if susceptible soybeans are going to be planted. Soil test bags with the submission form can be purchased at the Extension offices. If you need results quickly, test results can be sent via FAX or email if you provide the number or email address on the Nematode Assay Information Sheet. This information sheet can be found on the web at the Plant Clinic Website http://ag.udel.edu/extension/pdc/index.htm .

 

Small Grain Diseases

Friday, May 2nd, 2008

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Barley
Several diseases are present at this time. Powdery mildew, which we had reported earlier, seems to be found primarily on the variety ‘Thoroughbred‘. The spot blotch form of net blotch is also present in some varieties at low levels that should not affect yields. The latest “new” disease that appeared at heading is loose smut. This fungus is present in the seeds at planting and grows with the germinating plant and systemically infects the head and replaces the seed with its dark brown spore masses. Grain harvested from infected fields should not be used for seed unless it is treated with a systemic fungicide such as Baytan, Dividend, and Raxil. Because the spore masses weather and are absent during harvest the fungus does not cause surface contamination of the harvested grain so the feed value is not affected. Plant certified smut free seed and/or treat with a fungicide for loose smut control.

 

Loose smut of barley caused by Ustilago nuda

 Spot blotch and net blotch

Spot blotch on left two leaves, net blotch on right two leaves

 

Barley scald caused by a fungus Rhynchosporium secalis.

The last disease that I am seeing in barley is scald. This disease overwinters in old barley debris or can be seed borne. Look for the water-soaked gray-green spots that appear initially. As the lesion the dries out the center becomes bleached then tan with a brown margin (see photo). Some lesions can be very large and several spots can merge and kill the leaf. Rotation and use of resistant varieties is the best control method.

Wheat
Powdery mildew is still the most prevalent disease present. Continue to scout and remember that the end of flowering is the last opportunity to apply a fungicide for control. We have not confirmed it yet but I believe we have seen barley yellow dwarf mosaic virus (BYDMV) in wheat this week. A late fall infection or early spring infection produces symptoms of off-color wheat, which may be stunted in varying degrees, as well as red-purple flag leaves (the uppermost leaf). Since this virus is aphid transmitted, fields that are early planted or have had high aphid infestations are the most at risk. The later the infection occurs the less the effect on yield. Aphid control, including seed treatments, may prevent BYDMV as well as avoiding early planting.

 

Barley yellow dwarf causing reddened flag leaves

Flowering has begun for many wheat fields due to the warm weather last week. The remainder will be flowering in the next week or two. If you want to check the Scab Forecasting website visit: http://www.wheatscab.psu.edu/ for more info. Right now the risk for scab statewide for the next 48 hours is low.