Posts Tagged ‘barley diseases’

Small Grain Disease Update

Thursday, April 12th, 2012

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

The dry weather and low humidity has been very unfavorable for diseases at the present time. There are still some fields of barley with powdery mildew and leaf rust. If they needed treatments they should have been treated by now. Wheat is looking a bit better in that powdery mildew levels are low and except for some barley yellow dwarf mosaic virus in some areas the crop looks good. Rainfall is desperately needed. The risk for Fusarium head blight or scab is low at the present time. To keep track of the threat of scab be sure to check the website http://www.wheatscab.psu.edu/.

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.

Small Grain Disease Update – May 27, 2011

Friday, May 27th, 2011

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

Barley
The most prevalent diseases that can still be seen in areas where the barley has not returned yet are the spot blotch form of net blotch and powdery mildew. After checking the barley varieties today near Sandtown in western Kent County I don’t believe that net blotch will be affecting yields, but powdery mildew on unsprayed ‘Thoroughbred’ will reduce yields if the flag leaf is infected. There is some scab infected barley in Kent County.

Wheat
The wheat in the Kent County variety trial has tan spot moving in rapidly on some varieties. Most of the varieties are in the watery ripe stage of development and will not likely be adversely affected. Leaf rust was easily seen on a public variety ‘Rumor’. Powdery mildew in general was low in most varieties but was in the upper canopy on SS8302, Milton, Bravo, and USG3770. There is a low level of scab in the trial as well. If scab is going to appear it should be evident now or very soon depending on location. Low levels of scab (less than 1% of the heads infected and most of the infected heads were only partially infected) were present in 8 out of 45 varieties (around 18%).There is some sort of physiological spotting that could look like a disease but is probably a resistance reaction by the variety in response to a fungal infection. This spotting was evident on the following varieties at this Sandtown location: Merl, Sunburst,USG3665, USG3409, USG3251, and Grow Mark FS627.

 

Barley Leafspot Diseases

Friday, April 8th, 2011

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

As you scout your fields at this time of year it is often easy to find scattered brown spots in barley. Sometimes in wheat and rarely in barley, a minor disease called Ascocyta leafspot can be found on winter damaged tissue that can resemble Septoria leafspot but the plants grow out of it once warm weather arrives. The other brown spot that can be seen now is the early symptoms of net blotch. This is a very common leafspot of barley in our region. Severity is determined by the weather (it likes cool and wet) and the susceptibility of the variety. High nitrogen fertilization early will also favor development. Spot blotch rarely gets severe enough here to warrant fungicide applications. The symptoms that develop on barley can vary depending on the variety of the fungus present (there are several forms or isolates of this fungus) and the barley genetics. Later in the season we see the spot blotch form of net blotch (two leaves on the left) more frequently than the classic net blotch symptom seen on the two leaves on the right in the picture below.

Two leaves on left- spot blotch form of net blotch, on the right classic net blotch symptoms

Sometimes the only symptom development is a small brown spot or fleck that never enlarges or blights a leaf. This is thought to be the barley resistant reaction to the fungus infection.

The picture above, taken two days ago, shows the early symptoms on leaves before jointing has occurred. Typically, as the season warms the older infected leaves at the base of the plants will die and the new leaves may or may not develop more symptoms depending on the weather.

Agronomic Crop Disease Updates – September 17, 2010

Friday, September 17th, 2010

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

Corn
Corn harvest is underway so be sure to check corn fields for lodging potential by squeezing the lower nodes or pushing on the stalks. A simple way to do this is to walk through the field and, keeping your hands at chest height, push stalks 8-10 inches from vertical. If 10-15% of the stalks lodge, schedule the field for early harvest before a strong wind results in severe lodging. Drought conditions during grain fill put substantial stress on corn plants. In many fields, it is likely that the corn crop responded by cannibalizing stalk reserves to fill the grain. This results in a weakened stalk and greater susceptibility to stalk rot.

Small Grain
Be sure that you plant wheat 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 that will protect them from early infection.

Soybeans
Do not ignore soybean cyst nematode. Soil sampling after harvest before any fall tillage is recommended for fields to be planted next season to soybeans following this year’s crop. Do not plant SCN susceptible varieties without soil testing first. Soil sample bags are available from the county Extension offices for $10/ sample bag.

Soybean Rust Update
Nothing new has developed north of the North Carolina find on August 30. Florida had its first soybean rust detection on soybeans on September 14. Needless to say, soybean rust is not going to be an issue in most of the US this season.

Small Grain Disease Update – April 30, 2010

Thursday, April 29th, 2010

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

Keep scouting wheat for foliar diseases. Stripe rust is still a concern and is present in the South. Warmer weather will favor the Septoria, Stagnospora complex that causes speckled leafspot and glume blotch as well as common leaf rust and tan spot.

Last week I inadvertently did not include Twinline fungicide from BASF as another choice for powdery mildew control and other diseases on wheat and barley.

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.