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Options for Stripe Rust in Wheat

Stripe rust has exploded in wheat in the past 3-7 days in South-Central Nebraska due to theIMAG5065-1 rain and cooler weather.  Nebraska Extension is receiving numerous questions regarding options to consider.  Rain has also increased our risk for Fusarium Head Blight (head scab).

Wheat is at such a variety of stages in the area; many fields are just heading and/or flowering right now while others are in soft-dough.

Stripe rust on the flag leaf, as shown in this photo, will continue to progress with cool, wet conditions, reducing yield.  If your fields are currently yellow with stripe rust, here are a few options:

1-Do nothing and see what happens regarding what yield is obtained.  If your wheat is past flowering, fungicide application is not an option as all fungicides would be off-label.

IMAG5057-1

Susceptible wheat varieties to stripe rust that have not been treated with a fungicide to date have a yellow cast to them in South-Central Nebraska.

2-If your wheat is headed and beginning to flower, you could still consider a fungicide application of Caramba or Prosaro.  Both are labeled for headed and flowering wheat.  There’s a 30 day pre-harvest restriction for both.  Rainfast varies from ¼ hour to 2 hours or when dry depending on environmental conditions.  Both fungicides can help prevent scab and control rust on the plant. However, research has shown that best scab prevention occurs when wheat is headed and 30% of the plants are in the beginning flower stage.  Application within 5 days of these criteria still showed positive results.  Research showed that application before or after this time period greatly reduced effectiveness of preventing scab.  Understandably, the economics of a fungicide application are tight with current wheat prices.  The following article includes economic considerations.

3-Consider haying it.  Dr. Bruce Anderson, Nebraska Extension Forage Specialist shared the following:

“Baling hay or chopping silage are two potential options.  Rust pustules are not toxic to cattle although sometimes the spores can irritate respiration.  It can be difficult to make good silage, though.  Rusty leaves dry out rapidly so it can be hard to get the best moisture content for silage packing and fermentation.

Usually it is best to harvest rusty wheat hay just before heading to retain reasonable forage quality.  As plants mature further, quality can decline rapidly.  Digestibility of rust affected cells is much lower than that of normal cells.  Fortunately, protein doesn’t seem to be affected greatly.  Properly made hay should not deteriorate in the bale due to the rust any more than normal.

Be sure to have the forage tested before feeding.  It is likely that nutrient concentration will differ from typical wheat hay so testing will help in developing rations.  Also consider the impact of removing the wheat residue.  Adequate residue helps retain soil moisture, boosting yield of your next crop.

There never are good choices when problems like this develop.  All you can do is weigh your options and choose what is best for you.”

Also, please continue to check out UNL CropWatch for wheat disease and all our crop updates.

Wheat Scab Risk Increasing

Fusarium Head Blight Risk Assessment Tool: http://www.wheatscab.psu.edu/.

With wheat heading/flowering in South Central Nebraska and recent rains, risk for Fusarium Head Blight (scab) in wheat in our area of the state has increased to moderate/high.   

With wheat heading/flowering in South Central Nebraska and recent rains, risk for Fusarium Head Blight (scab) in wheat in our area of the state has increased to moderate/high.  I’m also finding stripe rust up to a leaf below flag with some just beginning to appear on the flag leaves. This year creates a harder decision for applying fungicides in non-irrigated fields with cost of production, wheat price, poor stands, and severe stripe rust. If you are considering a fungicide, your options during flowering are: Prosaro, Caramba, and Proline. Typical foliar fungicides are off-label once flowering occurs. The above-mentioned fungicides can help prevent scab and control stripe rust and some other foliar fungal diseases if the fungicide is timed correctly.  For preventing scab, research has shown that fungicides applied when approximately 30% of wheat heads reach beginning flower stage do a good job of protecting wheat plants as did the application of fungicide within 5 days of early flowering.  Application of the fungicide 7-10 days after flowering offered minimal control based on University research trials sponsored by the U.S. Wheat and Barley Scab Initiative.

Wheat Scab Potential Risk

With the recent rains in Nebraska, the potential for wheat scab has increased.  This video shares more information including a fungicide table of products to consider with product efficacy ratings for scab.  For more information, please check out http://cropwatch.unl.edu.  Thanks to Rachel Stevens, UNL Extension Intern, for producing this video!

The Season for #ag & #horticulture Questions!

This past week was a blur of calls, questions, and visits to homes and fields but it was a great week and flew by staying very busy!  I’ll touch on a few of the common questions I’ve received this week.

Trees:  Some trees such as willows, hackberries, tops of maple trees, ash, and black walnut are just taking time leafing out.  Some trees leafed out once already and dropped leaves.  Things that may have caused this were the sudden flux of temperatures from very warm to cool and the strong winds we received.  Some trees have also unfortunately had herbicide drift damage that caused leaves to drop.  On those trees, watch for new buds as nearly every situation I’ve looked at thus far have new buds forming after about a week-10 days.  With all these situations, give the trees a few weeks to leaf out again and if they’re still not doing it, feel free to give me a call.  Trees are interesting plants as sometimes environmental impacts that happened 3-5 years ago will show up that much later-and sometimes environmental impacts show up right away!

Disease/Insect issues:  This year has been a strange year all around but with our warm winter, I was concerned about an increase in diseases and insects.  Thus far, we’re experiencing increases in both-so hang on-it may be a long growing season!  Our high humidity, warm temps, and heavy dews have created perfect conditions for fungal diseases on our trees, ornamental plants, lawns (I’m currently fighting a bad case of powdery mildew-as a plant pathologist it is kind of pretty but I don’t like what it’s doing to my lawn!), and in our wheat and alfalfa crops and some pasture grasses.  Fungicides may help in some of these situations, increasing airflow can also help as can more resistant varieties or hoping the weather will change.  In the case of most ornamentals, we don’t usually recommend doing anything.  The same goes for insects as insecticides can help in some situations.  I’ve received several calls this past week of people afraid they had herbicide drift damage.  While there were a few cases of that, many of the cases were actually fungal leaf spots on leaves.  There are various fungicides and insecticide products available from home/garden centers, etc.  Be sure to read and follow all label directions and only apply the product on places the label specifies it can be applied.

Crops Update: Later this week we may have a better idea on the extent of storm damage and if some fields will need to be replanted after the storms from last week.  Dr. Bob Nielsen from Purdue University reported that most agronomists believe young corn can survive up to about four days of ponding if temperatures are relatively cool (mid-60’s F or cooler); fewer days if temperatures are warm (mid-70’s F or warmer).  Soil oxygen is depleted within about 48 hours of saturation and we know soil oxygen is important for the root system and all the plant’s life functions.   So we’ll have to wait and see what happens.

Have also had a few calls regarding rye cover crops.  When rye is killed out and decomposing, it releases toxins that can affect the germination of other cereal crops such as corn if it’s going to be planted into that rye cover crop.  Thus we recommend at UNL that the producer kill the rye and then wait at least two weeks to prevent any major damage to the crop.  I realize at this point with the rains to get in and kill that crop on top of waiting an additional two weeks, we’re getting close to the end of the month and will most likely be looking at reduced yields…and depending on maturity, you may need to consider different seed if you end up having to plant in June.  If you have specific questions about this, please let me know and we can talk through some situations.

Stripe rust and powdery mildew have been obliterating mid-lower canopies of many wheat fields.  I’ve received several calls on why wheat canopies are yellow-that’s the main reason but other factors such as the dry spell prior to these rains and/or deficiencies in nitrogen/sulfur or some viruses may also have been factors.  Wheat in Nuckolls County last week was beginning to flower.  Fungicides such as Prosaro, Folicur, or Proline are labeled for up to 50% flowering and cannot be applied after that.  Remember the wheat head begins pollination in the middle-so if you’re seeing little yellow anthers at the top or bottom of that head, you’re towards the end of flowering.  All those products have a 30 day pre-harvest interval-which has been the other main question-are we going to be harvesting in a month?  I do believe we’ll be harvesting a month earlier than normal just because pretty much everything in wheat development is about a month ahead of schedule.  I still feel the 30 day window for the fungicide application is worth it with the large amount of disease pressure we’ve seen. Wheat in Clay Co.  and north still may have time for a fungicide application; those products mentioned above will help prevent Fusarium Head Blight (scab) as well as kill the fungi causing disease already present on your leaves.  A list of all fungicide products, pre-harvest restrictions, and rates can be found here. Also check out my previous blog post with video on scouting for wheat diseases.  

The other major disease appearing in wheat is barley yellow dwarf virus.  This is a virus vectored by bird cherry oat aphids which we were seeing earlier this year.  Unfortunately, this disease causes the flag leaves to turn bright yellow-purple causing yield loss (at least 80% of the yield comes from the flag leaf) as there’s nothing you can do once the virus manifests itself in those leaves.  If you have a large incidence of barley yellow dwarf in your fields, you may wish to reconsider spraying a fungicide as the fungicide won’t kill the virus; however, it will help kill the fungi on the remainder of your leaves and potentially help protect some yield from the two leaves below the flag leaf.

#Wheat Disease Update

Questions have been rolling in regarding dead leaves in the mid to lower wheat canopy.  Wheat is heading in much of South Central Nebraska and in some cases has begun to flower.  When considering a fungicide application, once your wheat has begun to flower, there are only certain products that are labeled for use.  These include but are not limited to fungicides such as Proline, Folicur, and Prosaro.  All of these have a 30 day pre-harvest restriction and can only be applied up to 50% flowering.  For more information on all fungicides, rates, and pre-harvest restrictions for wheat, please check out this resource from Dr. Stephen Wegulo, UNL Extension Wheat Pathologist.  Below is a short video of me scouting a wheat field so you know what to look for in your fields.  Fungicides will not help leaves affected with barley yellow dwarf as that’s caused by a virus; however, with the amount of stripe rust in our canopies and seeing it on the flag leaves already in addition to the rain and humidity allowing for increased risk of Fusarium Head Blight (scab), I still feel a fungicide is a good option.  

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