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May 19 Wheat Update

Damage to heads from frost/freeze is beginning to appear as white awns/florets in wheat heads.  Thankfully this damage is very minor in area wheat fields right now.

Barley yellow dwarf is also appearing in fields and is noticeable by flag leaves with a yellow/purple color.  This is a disease vectored by various aphid species.  The aphid in this photo is a corn leaf aphid and I’m seeing these in wheat as well right now in addition to lady beetles which are feeding on them.  We also observed aphids last fall and were concerned about them potentially vectoring this disease.  I would say this is my least favorite wheat disease because you can do many things correct with wheat just to have this one show up and affect yield.

Stripe rust and leaf rust are also rapidly increasing in area fields with the humidity and moisture this past week.  Fungicide options differ right now dependent upon wheat growth stage.

Wheat flowering (pollinating). Look for the small yellow anthers. The wheat head will begin pollination in the center first and then pollinate the top and bottom.  I’m also concerned about the potential for Fusarium Head Blight (scab) in our wheat right now with all the rain we’re receiving during pollination.  Only a few fungicides are labeled for wheat during flowering and the ones that are can only be applied up to 50% flowering.  These include Caramba, Prosaro, Folicur, and Proline which are slated to help prevent scab and also kill fungal diseases like rust already present on the leaves.  Read and follow all pesticide label directions. 

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Also seeing some loose smut in fields which again is fairly minor.  Both loose smut and stinking smut (common bunt) can be prevented by using a seed treatment fungicide at planting.  Often these diseases occur in fields where wheat has been planted and smut has occurred before and when using bin-run wheat that has not been treated with a seed treatment fungicide.  Also notice all the yellow ‘flecks’ on these leaves which are indicative of fungal infection (most likely rust) on these leaves.

Crop Update May 5, 2017

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Received numerous alfalfa questions about browning and wilting of leaves/stems.  This photo shows those symptoms of frost/freeze damage.  

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Check the upper-most cluster of buds on alfalfa to determine any affects on regrowth. This is where the growing point is located.  Most of the alfalfa plants I’ve observed have healthy buds.  With the cool temperatures, regrowth has been delayed.  You may need to wait 7-14 days after the frost/freeze event to determine if regrowth is occurring from upper buds or from crown buds-and also to determine if an early harvest is warranted if there’s no regrowth from upper buds.  More information on alfalfa frost damage and management considerations

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I’m also observing alfalfa weevils in low numbers in alfalfa fields.  It will be important to scout your fields and monitor regrowth for second cutting.  More information on alfalfa weevil thresholds.

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Soybean planted April 21 at 2″ depth with good growth (I should have removed the soil from the root for this picture-did so after taking it and the root is healthy).  Corn planted April 24th, 48 hours prior to cold rains in Clay County, showing beginning germination and a healthy seed.  More information on potential chilling injury to corn and soybean seeds.

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Cooler temps last week slowed stripe rust of wheat which I found in low incidence April 26. Powdery mildew (gray/white spots in this photo) is still moderate-heavy in lower canopy.  April 6th was a beautiful day when I was in the area looking at crops, but with so many wheat fields with herbicide apps in that time-frame, I didn’t walk into fields to know how close wheat was to jointing.  Since then I’ve noticed a more sprawling growth to wheat instead of erect. This week I’m noticing thicker than normal nodes where wheat is trying to erect itself-and you can see that in this photo with the bent stems.  I’m not observing noticeable damage from frost/freeze at this time thankfully.  It will be important to watch as heads emerge for any difficulty emerging from the boot, damage to awns, or white colored florets/heads.   

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Germination of corn in York County Corn Grower plot planted April 22.  Soil temperature in the field that morning was 46F with a weekend of warm air temperatures.  

Wheat Updates-May 2016

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May 27: Wheat is in the milk to soft dough stages of filling with later heads still pollinating in Clay/Nuckolls county fields.  Stripe rust greatly increased in severity, particularly on susceptible varieties. This photo is showing progression on Overland.  I haven’t seen stripe rust yet in fields planted to Wolf.  Barley yellow dwarf is appearing in small amounts in more fields, but is limited to field corners/borders thus far.

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May 23: (Photo: barley yellow dwarf in wheat-characterized by yellow-purple flag leaves.  It is vectored by aphids). Wheat is in the late flowering to beginning milk stage in many Clay/Nuckolls county fields.  Stripe rust increased in severity this past week in more susceptible varieties and barley yellow dwarf is also appearing more often in patchy areas of fields.

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May 15: Rain is falling this morning in parts of our area and wheat is in a variety of heading and flowering stages.  While the risk management tool at:  http://www.wheatscab.psu.edu/ still says “low risk” I’ve been concerned it had the potential to be higher with our growth stage and weather conditions.  Last week I received numerous wheat fungicide questions.  Caramba and Prosaro are the two products you can apply legally once your wheat is flowering.  Twinline is off-label once flowering begins.  Yes, it has metconazole in it (also active ingredient in Caramba) in addition to a strobilurin, but it only legally can be applied to Feekes 10.5 which is full heading and is off-label once flowering occurs.  Caramba and Prosaro will help prevent scab in addition to kill the rust already occurring in your plants.  Unfortunately, I was also starting to see barley yellow dwarf appearing in Nuckolls County fields.  This virus is vectored by a number of aphid species.  We’d been seeing aphids and stripe rust for a month at this point but both remained below threshold levels/low incidence.  Barley yellow dwarf can be identified by the flag leaf turning a bright yellow-purple color.  With 80% of wheat yield coming from the flag leaf and there being nothing you can do about barley yellow dwarf, this also needs to be part of your decision making process if you were planning on applying a fungicide for preventing scab/controlling stripe rust.

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May 9: We’ve been seeing stripe rust in wheat for over a month now, but the amount of rust has remained low.  Some have chosen to spray wheat at this point; however I’m also concerned about the potential for Fusarium Head Blight (scab) in wheat.  Fusarium head blight is caused primarily by Fusarium graminearum, the same fungus causing Fusarium stalk, root, and ear rot in corn.  The fungus survives the winter in corn and other small grain residue and then releases spores in the spring.  However, wheat planted into soybean ground can still be affected by scab because the fungal spores can be wind-blown in addition to being water-splashed to wheat that is in the flowering stage.

According to research, wheat is susceptible from flowering through soft dough development stage.    “Typical” fungicides used for control of fungal leaf diseases are off-label thus illegal to apply once the wheat has flowered and they do not have activity on the Fusarium fungus causing scab of wheat.  Management for scab includes the use of the preventive fungicides 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.

Research from the US Wheat and Barley Scab Initiative (which is a combined effort of several Universities in the U.S. and Canada) has found that the best prevention using these products occurs when wheat is headed and 30% of the plants are in the beginning flower stage.  Application within five days of these criteria still showed positive results.  This research also showed that application before or after this time period greatly reduced effectiveness of preventing scab.  Understandably, the economics of fungicide application are difficult in wheat, yet, if you are aiming to make one application, this could be your best option for both scab prevention and controlling rust in your plants.  The risk map for scab can be found at:  http://www.wheatscab.psu.edu/.  With wheat at heading to beginning flower and rain/humidity this risk in reality could be higher for us.

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May 1: Wheat progressed quickly in one week!  Wheat in Clay and Nuckolls counties have flag leaves emerged even though wheat is really short.  The color is getting better thanks to moisture, root establishment, and nitrogen uptake.  I also didn’t see an increase in rust incidence this past week and aphid numbers were holding steady.  For those asking about fungicides, I’m still hoping we can hold off a little longer with current wheat economics, especially since in those counties rust wasn’t increasing due to the colder temps.  With warmer temperatures this coming week, please be checking your wheat.  If possible, one option that could be more economical in non-irrigated situations would be to consider treating your wheat once during flowering with either Caramba or Prosaro (as these products both prevent scab at the proper application timing and also kill fungal diseases including rust already present on the leaves).  We’ll have to see what happens with rust development and with how long it takes for heads to emerge.  There’s also been consistency with some varieties rated high for rust resistance where I have yet to find rust in them-so that’s a good thing!

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.

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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.

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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