Posts Tagged ‘wheat’

Frost Injury on Small Grains

Thursday, April 5th, 2012

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

Several weeks ago frost damage was identified on several barley fields, although it appeared to be limited to leaf tip burn (see Photo 1). Since that time, a number of other fields of both wheat and barley have shown similar symptoms and at least at this time the long-range weather forecast indicates a continuing risk for frost in the state and region. Barley fields have begun to head out and are quite susceptible to frost which can kill the pollen in the anthers preventing successful pollination and subsequent grain fill. Many times the only way we can determine if this has happened is to wait and see if the crop develops blank heads as maturity approaches. In the most recent issue of the Mid-Atlantic Regional Agronomist Quarterly Newsletter (March 2012), Dr. Wade Thomason from Va Tech wrote a review article entitled ‘What’s The Risk? Development of the 2012 Small Grain Crop and Potential for Spring Freeze Injury’. The article, as well as one I wrote for Weekly Crop Update April 13, 2007, gives the risk of injury from frost and the expected impact on wheat yield potential.

The Mid-Atlantic Regional Agronomist Quarterly Newsletter is posted on several web sites. Among these are the following locations: http://sites.udel.edu/equine/fact-sheets/forages-hay-and-pastures/ (look for the March 2012 issue) or http://www.grains.cses.vt.edu/ (look for Mid-Atlantic Regional Agronomy Newsletter) or www.mdcrops.umd.edu (click on Newsletter).

Photo 1. Leaf tip burn on barley from freezing temperatures (Kent County Delaware)

For First Split Nitrogen Applications on Wheat, Is Price per Pound of N the Right Criteria to Use?

Friday, March 2nd, 2012

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

There’s a debate going on as to what the best source of nitrogen (N) is for broadcasting over winter wheat or barley at this time of year. The question arises because it is known that urea can volatilize to ammonia (NH3), a gas, and be lost to the atmosphere because the enzyme urease, which helps break down urea, is present in all organic matter. What a lot of people overlook is the speed of this conversion which is affected by the soil pH, soil and air temperature, and moisture conditions. When temperatures are relatively low, below 70°F, and soil temperatures remain well below 50º, the activity of the enzyme is significantly reduced. Another factor involved is soil acidity or pH. When the soil surrounding the urea particle is acidic (pH<7.0), there are available hydrogen ions (H+) that can quickly react with ammonia to form an ammonium ion (NH4+). An ammonium ion is a cation that can occupy a place on the cation exchange sites in clay and soil organic matter and be held for plant absorption. The conversion of urea into ammonium bicarbonate and a hydroxyl (OH-) and then into ammonia (or an ammonium ion if an H+ is available), carbon dioxide, and water raises the localize soil pH and increases the likelihood that some of the N will volatilize off as ammonia.

In general, we found in the Deep South that you more economically apply urea to pastures or wheat fields in the early spring and often into mid-spring with only minor losses of N as ammonia. Since the soil temperature in Delaware soils seldom reaches the 50º F. level until well into April and we often have long periods of cool rainy weather in the spring, the choice of fertilizer to use on small grains is most likely best decided by economics rather than concern over just how much might be lost through volatilization. The most likely choices of fertilizer products are a urea ammonium nitrate solution (UAN) and granular urea. Since UAN does contain half urea and half ammonium nitrate, the small percentage N loss from ammonia volatilization is not likely to impact the economics between the two fertilizers very much. Growers should evaluate available fertilizers and choose the most economic fertilizer based on the cost per pound of N plus the expected application cost and the availability of the fertilizer through their usual dealer rather than arbitrarily sticking with what they’ve used in the past or what their dealer prefers to sell them.

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.

Small Grain Herbicides

Friday, September 9th, 2011

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

For the past two weeks I have written about weed control for winter wheat. The concepts and ideas I talked about are the same for barley and other winter grains. The following table is a list of herbicides labeled for the various small grains.

 

Herbicide Form. Active Ingredient MOA /

Grp #

Winter Wheat

Barley

Oats

Rye

   

Broadleaf Weeds

 

 

 

Harmony SG 50 SG Thifensulfuron 2

XX

XX

XX

 

Unity 75 DF Thifensulfuron 2

XX

XX

XX

 

Harmony Extra 50 SG thifensulfuron +

tribenuron

2 + 2

XX

XX

XX

 

TNT Broadleaf 75 DF thifensulfuron +

tribenuron

2 + 2

XX

XX

XX

 

Starane Ultra 2.8 L Fluroxypyr 4

XX

XX

XX

 

2,4-D various 2,4-D 4

XX

XX

XX

XX

dicamba (Banvel) 4 S Dicamba 4

XX

XX

XX

XX

Finesse 75 DF chlorsulfuron +

metsulfuron

2 + 2

XX

POST only

 

 

   

Numerous Grasses / Broadleaves

 

 

 

Osprey 4.5 WG Mesosulfuron** 2

XX

 

 

 

Axiom 68 DF flufenacet + metribuzin 15 + 5

XX

 

 

 

PowerFlex 7.5 WG Pyroxsulam 2

XX

 

 

 

   

Strictly Ryegrass

 

 

 

Hoelon 3 EC Diclofop 1

XX

XX

 

 

Axial XL 0.42 L Penoxaden** 1

XX

XX

 

 

   

Seldom Recommended

 

 

 

Peak 57 WDG prosulfuron 2

XX

XX

XX

 

Stinger 3 L clopyralid 4

XX

XX

XX

 

Buctril 4 EC bromoxynil 6

XX

XX

XX

 

Aim 2 EC carfentrazone 14

XX

XX

XX

 

Prowl H2O 3.8 ACS pendimethalin 3

XX

 

 

 

Maverick 75 WG sulfosulfuron 2

XX

 

 

 

*Finesse is labeled in barley for postemergence applications only
**Also contains a safener

Related Articles:
Considerations for Weed Control in Winter Wheat I
Considerations for Weed Control in Winter Wheat II
Metribuzin Use in Winter Wheat

Weed Control in Winter Wheat

Friday, September 2nd, 2011

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

In last week’s issue of Weekly Crop Update I explained why we need to consider fall herbicide treatments for small grains. When splitting nitrogen applications in the spring, neither one of the timings are a good for herbicide application when trying to achieve spraying small weeds that are actively growing and achieve good coverage.

1. Weeds are more susceptible in the fall.

2. Fall applications match better with weed development.

3. Weed emergence is primarily in fall.

4. Fall herbicide applications are not influenced by temperature as much as spring applications.

5. Coverage is better with fall applications.

6. Spreads out the workload.

For no-till fields, a non-selective herbicide needs to be used prior to planting. However, we do not have effective herbicides labeled for preemergence applications, so it is important that the field be scouted to ensure the crop is at the proper stage for herbicide application.

A few products can be used shortly after the crop has emerged. Axiom and Prowl H2O can be used at crop emergence (Axiom at the spike stage and Prowl H2O at 1 leaf stage); however they need to be tankmixed with other herbicides or followed by postemergence herbicides to provide a broad spectrum control.

Products that provide postemergence control include: Harmony, Harmony Extra, Starane Ultra, Osprey, PowerFlex, Axial XL. Others labeled with a limited fit include metribuzin, Finesse, Maverick, 2,4-D or dicamba.

Control of specific problem weeds:

Annual bluegrass: fall applications of Osprey are the most consistent. Fall application of PowerFlex is also good. Maverick is a last resort type treatment in the spring (Maverick requires use of STS soybeans).

Annual ryegrass: fall applications of Osprey, PowerFlex, or Axial XL work extremely well. Spring applications of PowerFlex and Axial XL are options, but neither can be applied in nitrogen without reducing the amount of nitrogen applied.

Roughstalk bluegrass: Osprey or PowerFlex perform well on this species.

Speedwells: We have had limited trials with the speedwell species, but fall treatments seem to be most consistent. Harmony Extra has little to no effect on this species, PowerFlex in the spring was rated as fair to good; and slightly better than Osprey (fair). Research at Virginia Tech has shown good results with Finesse postemergence, but this treatment requires the use of STS soybeans. Initial results with metribuzin show some utility for speedwells.

Jagged chickweed: This is another species we have limited trials for, but fall applications seem much more effective than spring treatments. Osprey, Harmony Extra, and PowerFlex seem to work well when applied in the fall.

ALS-resistant chickweed: This species is on the move with more reports each year. Harmony Extra, Osprey, and PowerFlex are all ALS herbicides (Group 2) and have no activity on this biotype. Rather, Starane Ultra or metribuzin in the fall have been the best treatments.

ALS-resistant horseweed: Another species with no trials. Starane Ultra lists horseweed as a species it will suppress. We do know that 2,4-D will control horseweed in burn-down situations, but we have not looked at low rates of 2,4-D in wheat for crop safety and effectiveness.

One common weed that is not controlled with fall applications is wild garlic.  But this weed needs to be treated with Harmony Extra (or similar products) in the early spring, about the time we apply the second nitrogen application.  We need to think of wild garlic (a late emerging perennial) separately from the annual weeds mentioned above.

A rotation to vegetables is an issue with many of these herbicides, including Osprey, PowerFlex, Finesse, Maverick, and metribuzin. Starane Ultra is a 4 month rotation to most crops. As you can see there is no one program that will provide control of all of our problem species. In most situations, a fall treatment will outperform a spring application, and you need to select the herbicide(s) based on the problem weeds you have in your field.

Metribuzin Use in Winter Wheat

Friday, September 2nd, 2011

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

Metribuzin is a product used for years in soybeans and other crops for broadleaf weed control (formerly called Sencor or Lexone). It has been labeled for use in winter wheat, but the label does not recommend its use in our region. Metribuzin is one of the active ingredients in Axiom, and so it has been used on a limited basis in our region. Since metribuzin is a generic product there are different products available, but most go by the name metribuzin or some close version of this spelling.

After identifying ALS-resistant chickweed and looking for potential control options I began testing metribuzin, along with a number of other weed specialists in the region. We have had good results with control and very little injury with metribuzin.

The label reads, “metribuzin alone or with tank-mixture treatments are recommended for use in the following states” and none of the states in the Mid-Atlantic region are included. On the other hand, the label does not prohibit the use of metribuzin. Metribuzin label does allow for tankmixing herbicides, to broaden the spectrum of control. We have not tested all the possible combinations with newer herbicides (Axial XL, Osprey, or PowerFlex).

Rate is dependent on soil type and growth stage. Application timing is from 2-leaf stage of the wheat until 4 tillers. We have tested metribuzin primarily for ALS resistant common chickweed, and rates of 2 to 4 oz applied with a nonionic surfactant have worked quite well.

Some precautions on the label include: Do not apply to stressed crop (including dormant, drought, frost damage, disease); do not apply with liquid fertilizer; do not use on soils with less than 0.75% organic matter; do not apply more than 0.5 inches of irrigation for the first irrigation after application and do not exceed 1 inch for any subsequent irrigation; wheat varieties differ in sensitivity (some are more sensitive than others).

Metribuzin is also labeled for barley, but we do not have experience with it.

Considerations for Weed Control in Winter Wheat

Friday, August 26th, 2011

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

As we approach fall and planting wheat, it’s time to consider options for weed control. A few species have become more troublesome, and I attribute a lot of this to the way we have been approaching weed control. Most herbicides go out in the spring with nitrogen. While this might be acceptable for many fields, it is often not the most effective application timing. When splitting nitrogen applications in the spring, neither one are a great timing for herbicide application. The first nitrogen application is applied when the wheat is beginning to “green-up” after the winter, so this is before the wheat is actively growing (also means that the weeds are not actively growing). The second nitrogen application is after tillering and just before stem elongation (means weeds have grown considerably in the spring from first application of nitrogen and much taller than 3”, and wheat growth prevents good coverage; both reducing the effectiveness of the spray). This is contrary to all recommendations which are: spray small weeds that are actively growing and achieve good coverage.

UD Weed Science Program has been looking at herbicide applications to winter wheat in the fall. Typically these treatments are going out in middle to late November. Some of the reasons this approach have been successful are:

1. Weeds are more susceptible in the fall. As I pointed out they are smaller and actively growing. Furthermore, fields with heavy poultry litter applications or excess nitrogen tend to have lots of weed growth in the fall and this contributes to even worse control in the spring.

2. Fall applications match better with weed development. As noted weeds are smaller the earlier they are sprayed. Furthermore, most annual species will progress to flowering early in the spring which can reduce herbicide performance as well.

3. Weed emergence is primarily in the fall. Some emergence occurs in the spring, but most occurs in the early fall. Fall emerging weeds are more detrimental to yield than spring emerging weeds. And, if there is significant spring emergence, then a herbicide treatment with the second split of nitrogen will be beneficial for these small seedlings.

4. Fall herbicide applications are not influenced by temperature as much as spring applications. It is usually late into March that we start to get consistent temperatures above 55°F. In the fall, heavy frosts have occurred by mid November, but soil temperatures allow for active plant growth during the days. Therefore, we have better environmental conditions for control in the fall than early spring.

5. Coverage is better with fall applications. See notes above

6. Spreads out the workload. And if all the best planned strategies do not get implemented in the fall, you have a back-up plan for treating in the spring (albeit not as effective as fall).

I realize some spring herbicide applications are necessary such as: wild garlic control (but Harmony Extra can be applied with the second nitrogen applications); other perennial species that emerge in the spring (Canada thistle or bulbous oatgrass); or late planted fields when the crop may not reach the stage for safe application. But fields with a history of poor weed control, should be targeted with fall applications.

Next week will be a review of available herbicides for fall applications.

 

Head Scab and the Relationship to Saved Seed and Vomitoxin Production

Friday, June 10th, 2011

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

Head scab has been observed in barley and wheat this season in varying amounts. Barley is just now arriving at the grain elevators. The amount of scab that occurs is dependent on the flowering time, the presence of the scab spores that infect the heads during flowering and the weather conditions during flowering. Most of the barley and wheat varieties that we grow have little or no resistance to head scab. The fungus can be present on old corn stover, and residues of old barley and wheat crops. What drives this disease is wet, warm weather during the flowering period. If the heads of barley or wheat are infected with the fungus (Fusarium graminearum) that cause head scab, that fungus can produce several toxins that can contaminate the grain. These toxins are often referred to as vomitoxins because they can cause feed refusal in non-ruminant animals. The most common vomitoxin that is produced by the head scab fungus is deoxynivalenol or DON for short. DON production by the fungus is extremely variable depending on environmental conditions. The presence of scab on the grain does not mean that the grain has to have DON nor does high or low levels of scab relate to the amount of DON present. A high level of scabby kernels in the harvested grain means that DON will likely be present.

What about the saving or using seed from scab infected fields? As much scabby wheat kernels as possible should be removed from good seed during combining and seed cleaning. This is not easily done with barley or may not be possible because barley does not get as light as wheat. Saved seed kernels can be infected with Fusarium, and seed treatments can reduce the effects of Fusarium on seed. Fusarium on seed can cause a seedling blight of barley and wheat but the seedling infections do not result in head scab or DON in fields that might be planted with infected seed. In fact some studies have shown a reduction of scab infections in seed during storage. Low levels of scab infected wheat or barley can be saved for seed if properly handled and treated without any risk of scab occurring in the crop from that seed.

Another issue for barley producers is that the threshold levels of DON in wheat may not be the same compared to barley presuming that the barley is not intended for human consumption. The DON threshold for wheat is 1 ppm because of human consumption concerns. Barley for feed can have up to 10 ppm without harmful effects depending on the animals being fed and the proportion of infected grain being fed. In my opinion barley should not be held to the same threshold as wheat depending on its destination or final use. See the following information on DON levels in food and feed.

What are the critical levels of DON for use in food and feed?
The concentrations of DON in grain are expressed as parts per million (ppm). One ppm is equivalent to 1 pound in 1 million pounds, 1 penny in $10,000, 1 minute in two years, or 1 wheat kernel in 80 pounds of wheat. The U.S. Food and Drug Administration (FDA) has established DON advisory levels to provide safe food and feed. Unlike aflatoxin in corn, DON is not a known carcinogen. Furthermore, grain with DON would have to be ingested in very high amounts to pose a health risk to humans, but it can affect flavors in foods and processing performance. Human food products are restricted to a 1-ppm level established by the FDA. This level is considered safe for human consumption. The food industry often sets standards that are more restrictive. DON causes feed refusal and poor weight gain in some livestock if fed above the advisory levels. FDA advisory levels are as follows:

1 ppm: Finished wheat products, such as flour, bran and germ that potentially may be consumed by humans. The FDA does not set an advisory level for raw grain intended for milling because normal manufacturing practices and additional technology available to millers can substantially reduce DON levels in the finished wheat product. However, individual millers or food industries may have stricter requirements than 1 ppm.

10 ppm: Grains and byproducts destined for ruminating beef and feedlot cattle older than 4 months and for poultry, providing that these ingredients don’t exceed 50 percent of the diet.

5 ppm: Grains and grain byproducts destined for swine, providing that these ingredients don’t exceed 20 percent of the diet.

5 ppm: Grains and grain byproducts destined for all other animals, providing that these ingredients don’t exceed 40 percent of the diet.

Taken from NDSU Fact sheet PP-1302, DON (Vomitoxin) in Wheat. http://www.ag.ndsu.edu/pubs/plantsci/pests/pp1302.pdf

 

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.