Posts Tagged ‘loose smut’

Small Grain Disease Prevention

Friday, September 23rd, 2011

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

Be sure that you plant wheat and barley varieties with high levels of disease resistance. Select varieties with high levels of resistance to powdery mildew, leaf rust and stripe rust. Seed should be treated with Baytan, Raxil, Dividend or other labeled product to protect plants from loose smut and common bunt. Varieties that are susceptible to powdery mildew should be treated with Baytan, Dividend, or other seed treatment fungicide that will protect them from early infection.

Prevention of Disease in Small Grains

Friday, September 12th, 2008

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

Be sure to plant fungicide treated seed for control of loose smut and common bunt especially if you saved your own seed for planting. Select varieties that are high yielding as well as resistant to powdery mildew, leaf rust and stripe rust.

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.

Several Pest Management Issues to Think About if You are Saving Cover Crop Wheat or Barley for Grain Production

Friday, March 28th, 2008

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu and Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

With the high prices of wheat and barley some cover crops may be kept for grain instead of plowing them under. As long as the stand is sufficient for economical yield the fields can be managed for grain production. There are several pest management issues that could be a problem if you have decided to do this. Loose smut is a systemic fungus disease that is transmitted in infected seed. Infected seed looks healthy and germinates as if it were not infected. When the seed germinates the fungus is activated and systemically grows within the young seedlings. The fungus remains in the plant over the winter and when growth resumes the fungus grows with the plants and eventually to the head where the fungus spores replace the wheat or barley kernel and other flower parts. The only window to control this disease, if the seed is contaminated, is with a seed treatment for loose smut at planting. If the cover crop seed was certified and/or treated with Baytan, Raxil, Vitavax, or Dividend at rates for loose smut control, the crop is protected. Currently there is no labeled foliar fungicide for wheat or barley that will control loose smut if the plants are infected. There is no way to tell if the crop is infected until heading, so if you planted untreated, saved seed or untreated seed from an unknown source there is a risk of loose smut at heading.

Since cover crops are often planted before production fields, Hessian fly could be a potential problem. Fields planted well before the “fly free” dates (New Castle County -Oct 3; Kent County – Oct 8 and Sussex County- Oct 10) could have been exposed for a longer time to egg laying by Hessian fly adults. Any eggs laid in the cover crop wheat hatched into maggots which fed on that wheat and then changed into pupae (called flax seeds) to survive the winter. When the Hessian fly adults emerge from the flaxseed this spring, they will seek a host upon which to lay their eggs. Since wheat is the principal host plant of the Hessian fly and they are not strong flyers, these fields may be susceptible to spring infestations. Please refer to the article “Management of Hessian Fly in the Spring” in WCU Volume 16, Issue 1 for sampling and possible control options.