Posts Tagged ‘small grains’

Small Grain Diseases

Friday, March 2nd, 2012

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

Powdery Mildew on Small Grain
Be on the lookout for powdery mildew on ‘Thoroughbred’ barley and wheat. Powdery mildew has been seen on both within the last several weeks. ‘Thoroughbred’ barley is very susceptible to PM as you know and if the stand is thick and lush you will more than likely see it. Does it need to be controlled this early in the season? I think it depends on how many times you are willing to spray it. Dr. Arv Grybauskas did a trial last season looking at fungicide applications at jointing (GS6), flag leaf emergence (GS9) and flowering (GS10.5) Tilt (4.0 oz/A) was applied at GS 6 or 9 and Prosaro (6.5 fl. oz/A) was applied at GS 10.5. While all treatments gave a positive yield response in two trials, only the later applications gave a significant yield increase. It confirms what we have been saying about the importance of keeping the top two leaves free of disease and the positive relation to grain fill. This is true in wheat and susceptible barley like ‘Thoroughbred’. If you spray to control mildew at jointing you may have to come back again later because the control will not last season-long. Disease control later is more important for protecting the yield potential of the crop.

For powdery mildew on wheat, check areas of rank growth first to see if the disease is present in the field then revisit to see if it spreads. It is too early to consider control of powdery mildew (PM), but if it is present, keep scouting. Unless the variety is very susceptible the mildew does not move fast depending on the weather.

Rank areas, like the one pictured here that was infected with powdery mildew, should be checked often.

Close-up of powdery mildew as it looks now

Rust on Small Grain
Everyone has been wondering about the possible consequences of the warm winter and one consequence might affect wheat. Both leaf rust and stripe rust have been found in the South this winter. It has been mild and relatively moist depending on the location. This scenario is conducive for rust infections that get started in the southern production regions and blow north as the season progresses. With the early appearance down south, the mid-Atlantic area may see rusts early enough to be a threat. Keep your eyes open as the season progresses.

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.

Harvest Aids for Small Grains

Friday, June 3rd, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

A number of glyphosate products such as Roundup and Touchdown are labeled as harvest aids in winter wheat and barley. Check the label for other formulations of glyphosate. Applications must be made after the hard-dough stage and at least 7 days prior to harvest. Aim is labeled as well, but the spectrum of control is limited to velvetleaf, morningglory, pigweeds, and few other weeds. Apply at least 3 days before harvest. Use of 2,4-D (or products containing 2,4-D) is generally not recommended as a harvest aid due to its volatility, and potential damage to the crop during application.

 

Agronomic Crop Disease Updates

Friday, June 3rd, 2011

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

Soybeans
The dry conditions combined with high soybean cyst nematode (SCN) egg counts could mean we will see more stunting from SCN this season. Be on the lookout for stunting in irregular areas. The SCN females can be seen on the roots of infected soybeans around 28-32 days after planting.

Barley
Barley harvest is fast approaching and the crop looks pretty good. Besides some leaf rust, net blotch, powdery mildew on ‘Thoroughbred’, and a little head scab, diseases have not been bad this season.

Wheat
A few diseases were observed during a recent check of the variety plots near Middletown in New Castle County. Low levels of tan spot and powdery mildew were seen in a few varieties, but all but one of the 45 entries had some head scab. Most of the infections were under 1% of the heads infected and many of those heads were only partially infected. Wheat in NCC was the most at risk according to the scab predictions. Some shriveled grain with the white coating of the Fusarium fungus was observed on some of the infected heads. Increasing fan speed on the combine will blow the light chaffy “tombstones” out the back and not contaminate the rest. Planting multiple wheat varieties with different flowering times (maturity) will decrease the risk of scab for next year. Statewide, overall scab levels are low compared to several years ago. I had mentioned in last week’s WCU that several varieties in the variety trial had genetic flecking or a resistance reaction including Merl, USG 3209, USG 3251, USG3665, Sunburst, and Grow Mark FS627. These symptoms are not an active disease.

Flecking on USG3409 that looks like a disease

Head scab on wheat

Healthy kernels and Fusarium head scab infected “tombstones”

Tan spot on wheat

 

Harvesting Grain from Scabby Fields
The following are tips to reduce the amount of scabby kernels in the harvested grain and to avoid potential health problems for combine operators and grain handlers. Scabby grain is contaminated with mycotoxins, especially vomitoxin, which is harmful to humans.

Harvest tips:
1. Avoid breathing in dust from scabby fields by using a high quality dust mask. Spores of the scab fungus (Fusarium graminearum) and small pieces of contaminated plant parts are present in the dust. Inhaling these particles may cause health problems.

2. Harvest the most severely scab damaged areas, such as low areas or double seeded headlands, separately. Don’t co-mingle the most damaged grain with sounder grain.

3. Turn up the air on the combine to blow out the lightest, scabby kernels back into the field.

4. If rain is forecast, it may be better to harvest scabby fields at slightly higher moisture content than to wait for grain to dry down. However, this grain still needs to be dried down and maintained below 15% moisture after harvest to prevent fungal growth in storage.

5. After harvest, gravity table grain separation can be used in removing more of the light-weight, scabby kernels.

6. Get grain from scabby fields tested for vomitoxin before feeding, before blending, or before making a decision to discard suspect grain.

From http://www.scabsmart.org/harvest%20practices.html

 

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.

 

Small Grain Disease Update – May 20, 2011

Friday, May 20th, 2011

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

Fusarium Head Blight (Scab) in Wheat Update: Although the recent weather pattern early this week has been favorable for head scab in wheat, most of the wheat in Sussex and Kent County has completed flowering by now and not likely to become infected with scab. If you have wheat that is flowering now consider a fungicide application of Caramba or Prosaro. Wheat that is about 5 days or more past initial flowering cannot be treated. The labels state the last stage of application is mid-flower and there is a 30-day to harvest restriction.

Scab identified on barley. We just received a sample of ‘Nomini’ barley from Kent County and have confirmed a scab (Fusarium head blight) infection on the top 6-7 kernels. The sample was only two heads and several plants but growers will want to keep an eye out for bleached heads on barley from here on out. Nothing can be done now but increasing fan speed on the combine at harvest which can help blow the lighter chaffy infected grains out of the combine. Hopefully this turns out to be an isolated find.

 

Small Grain Disease Update – May 6, 2011

Friday, May 6th, 2011

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

Wheat
Be sure to keep scouting for the presence of diseases, especially powdery mildew, at this time. With the return of cooler temperatures and risk of showers and cloudy weather as well, powdery mildew could become a problem, especially in very thick stands of susceptible wheat. It is important to keep the uppermost two leaves as free of diseases as possible to protect yields. At the most, you can wait until you see 5-10% of the upper two leaves infected before applying a fungicide. Tilt, Stratego, Twinline, and Quilt can be applied as late as heads emerged but not yet flowering. If scab should be a concern this year it may be best to use only a triazole fungicide at heading through flowering to avoid mycotoxin issues if scab infection occurs. There is evidence that if fungicides containing strobilurins (Quilt, Twinline, Stratego) or strobilurins alone are applied during heading up to flowering, they can increase mycotoxin production if scab occurs during flowering. If a fungicide is needed as late as flowering for powdery mildew, Septoria leaf blotch, tan spot, or other disease and conditions are favorable for scab development consider applying Prosaro, Caramba, or Folicur for scab suppression and control of the other diseases just mentioned. For a table that rates the efficacy of fungicides for use on wheat diseases see the following link to the Kansas State fact sheet with the NCERA-184 ratings. This is a group of wheat pathologists from across the country that collaborates on wheat disease control. http://www.ksre.ksu.edu/library/plant2/ep130.pdf

Head Scab Risk Assessment Tool
Scab is still the one wheat disease that can cause major economic losses if weather conditions are favorable prior to and during flowering. The tools that we have to manage scab are limited but the use of rotation, resistant varieties and fungicides can help reduce the losses from scab should it appear. One of the tools that we have to help predict its occurrence and aid in making fungicide application decisions is the Head Scab Risk Assessment Tool that is found on the wheat scab website http://www.wheatscab.psu.edu/. The site provides information on how to use the tool and its limits.

 

Small Grain Disease Update – April 29, 2011

Friday, April 29th, 2011

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

Wheat is developing rapidly with the recent increase in temperature. Be sure to keep scouting for the presence of diseases, especially powdery mildew, at this time. It is important to keep the uppermost two leaves as free of diseases as possible to protect yields. At the most, you can wait until you see 5- 10% of the upper two leaves infected before applying a fungicide. Tilt, Stratego, Twinline, and Quilt can be applied as late as heads emerged but not yet flowering.

If scab should be a concern this year it may be best to use only a triazole fungicide at heading through flowering to avoid mycotoxin issues if scab infection occurs. There is evidence that if fungicides containing strobilurins (Quilt, Twinline, Stratego) or strobilurins alone are applied during heading up to flowering, they can increase mycotoxin production if scab occurs during flowering. If a fungicide is needed as late as flowering for powdery mildew, Septoria leaf blotch, tan spot, or other disease and conditions are favorable for scab development consider applying Prosaro, Caramba, or Folicur for scab suppression and control of the other diseases just mentioned. For a table that rates the efficacy of fungicides for use on wheat diseases see the following link to the Kansas State fact sheet with the NCERA-184 ratings. This is a group of wheat pathologists from across the country that collaborates on wheat disease control. http://www.ksre.ksu.edu/library/plant2/ep130.pdf

Head Scab Risk Assessment Tool
Scab is still the one wheat disease that can cause major economic losses if weather conditions are favorable prior to and during flowering. The tools that we have to manage scab are limited, but the use of rotation, resistant varieties and fungicides can help reduce the losses from scab should it appear. One of the tools that we have to help predict its occurrence and aid in making fungicide application decisions is the Head Scab Risk Assessment Tool that is found on the wheat scab website http://www.wheatscab.psu.edu/. The site provides information on how to use the tool and its limits.

 

Small Grain Weed Control

Friday, April 22nd, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

I have looked at a few fields of winter wheat or barley where growers were concerned about lack of weed control. Turns out these fields had jagged chickweed or speedwell in them, which spring applications of Harmony Extra do not control. Based on our observations either Osprey or Harmony Extra applied in the fall did do a good job of controlling jagged chickweed. Speedwells are not controlled with Harmony Extra. We have trials this spring and will have more to share with you by fall, but most of the products that can be sprayed this late in the season do not control speedwell.

For wild garlic control, Harmony Extra is the product of choice and the label allows two applications per season. But, be sure to read the label for the total amount that can be used per season.

Common chickweed

Common chickweed

Jagged chickweed

 

Barley With Multiple Nutrient Deficiencies

Friday, April 22nd, 2011

Richard Taylor, Extension Agronomist; rtaylor@udel.edu and Phillip Sylvester, Kent Co., Ag Agent; phillip@udel.edu

Another field of barley with severe deficiency symptoms showed up in Kent County this past week. Although the field had received ammonium sulfate this spring, the rate used provided only about 10 to 15 lbs of S per acre, which is less than the crop requirement. If the low S fertilization rate is coupled with the heavy rainfall many areas have experienced over the past several weeks, it would not be surprising that a significant amount of the sulfate-S has leached below the rooting zone of barley. In this case, although the visual symptoms (Photo 1 and 2) suggested sulfur (S) deficiency with general chlorosis of the leaves, especially the newest leaves, and shortened plants, the soil test suggested that S was not the only deficiency likely to impact barley yield even if sulfur were added (Table 1). On the bad sample note the low soil organic matter (SOM) level (0.9%) and the impact on the cation exchange capacity (CEC) of the soil (2.1 meq/100 grams of soil in the bad area versus 3.6 meq/100 grams of soil in the good area). The CEC impact was also evident in the amount of potassium (K) and magnesium (Mg) that the soil could hold.

Photo 1. Close-up of deficient barley plants showing general chlorosis, especially in newest leaves, and stunting.

Photo 2. Field view of deficient barley plants showing general chlorosis and stunting compared with less affected plants in the background.

The short term solution to the problem is the addition of K-Mag (0-0-22-11Mg-22S) fertilizer to the field. However, the soil test results suggest that on a longer-term horizon, the critical need of the field is the addition of organic matter, either as green manure crops, compost additions, or manure additions. Trying to maximize the amount of crop residue and minimize the amount of SOM mineralization due to tillage operations is also recommended. The use of winter cover crops and green manure crops whenever the field is not being cropped will gradually raise the SOM levels, as will any additions of manures or composts. Not only with organic will additions help raise the CEC and soil nutrient holding capacity but will also help increase water holding capacity and improve yields in the long run.

Table 1. Soil test report on barley field comparing good and bad areas.

Good Barley Bad Barley
Soil pH 1:1 6 6.3
Buffer pH 6.9 7
Organic Matter % 2.4 0.9
U of D P Sat Ratio 39 59
Mehlich3 Phosphorus ppmP/FIV 193 144
K ppm 98 54
Ca ppm 442 275
Mg ppm 74 44
SO4-S ppm 20 7
Zn ppm 4.56 2.99
Mn ppm 61 15
B ppm 0.36 0.16
CEC meq/100g 3.6 2.1
H* 15 10
K* 7 7
Ca* 61 65
Mg* 17 18
Na* 0 0

*Indicated Base Saturation