Crop Update: So grateful for rain and truly hope those who wanted and needed rain received it! An update to soil moisture profile as of 5/17/18 can be found at http://jenreesources.com.
A number of crop issues surfaced this week. One being root burn and wilted-looking corn seedlings from anhydrous ammonia applications with the dry winter/spring we’ve had thus far. Anhydrous ammonia can expand in soils 2.5-3” in all directions and potentially more in dry soils. Pivots were running to help with that and hopefully rain events will help non-irrigated fields that were suffering in this way. Another problem observed in some non-irrigated corn fields has been fomesafen carryover injury from products such as Flexstar, Reflex, Prefix, etc. These products have a 10 month planting window back to corn which is fine in most years, but dry conditions didn’t allow for the herbicide to break down in all situations from applications last June. This active ingredient is in Group 14 (PPO inhibitors) and the injury from this particular active ingredient is unique in that it causes yellow/brown striping of the veins themselves instead of interveinal chlorosis/necrosis. Seedlings most affected right now are found on field edges or wherever there was overlap of application. Hopefully corn should grow out of this injury in time. Herbicide carryover may be a something to watch for in soybean as well from other active ingredients. We also saw regrowth occurring on plants affected by wind/dust/debris damage but there are situations where replanting will be needed on endrows, etc. Roger Elmore has a photo gallery explaining regrowth in this week’s CropWatch at http://cropwatch.unl.edu.
Another situation that surprised me this year was finding seed corn maggot damage in
soybean. At first I was puzzled as the beans were clearly treated but then learned the beans didn’t have an insecticide added to the seed treatment. In scouting a number of fields, I’ve actually seen quite a bit of seed corn maggot damage, particularly in tilled fields and those with manure applied or those with cover crops that were green or where termination included tillage. I’ve also been surprised how many have told me they don’t use an insecticide seed treatment on early planted beans. We didn’t have any research in our early soybean planting studies without insecticide + fungicide seed treatment so we just automatically recommend both. Unfortunately this year we’re seeing what can happen without it with higher insect pressure in some fields. For seedlings with the insecticide seed treatment, I’m seeing light scarring on the cotyledons and hypocotyls but no maggot penetration. In fields without the seed treatment, I’m actually seeing penetration of the cotyledons and hypocotyls. The good news is that most of the maggots were also pupated, pupating or will be soon. But it is something to watch for, particularly in fields that have been tilled and especially if manure was applied or they were tilled and had a cover crop on them. They are not as attracted to no-till fields. Regarding stands, from my experience with soybean pops and stand loss due to crusting, hail, herbicide injury, etc., I keep stands of 60,000 plants/acre or more. It really stinks to talk about replanting anything right now with guys still trying to finish planting. If you choose to replant soybeans, consider proving it to yourself by planting strips and leaving strips. If you’re interested in that, I’d be happy to work with you. You can learn more about seed corn maggots here: https://crops.extension.iastate.edu/cropnews/2016/04/look-seedcorn-maggot-corn-and-soybean.
Wheat in the area ranges from boot to flowering. A couple of wheat fields I know of
were taken for hay. For those still considering silage, check out the CropWatch article this week where Todd Whitney shares data on wheatlage (wheat silage): https://go.unl.edu/qkbr. The rainfall will greatly help our wheat right now. And, rainfall at heading to flowering makes me think about the potential for Fusarium Head Blight (scab). The wheat scab prediction monitor http://www.wheatscab.psu.edu/ is predicting medium to high risk for scab in Nebraska for the next 48-72 hours. Some years I feel the model is delayed in prediction, but I still feel it’s a good tool and resource. Scab is caused by Fusarium graminearum and is favored by warm (70-80°F temps), humidity, and rain events before and during flowering. Once wheat begins flowering (Feekes 10.5.1), many foliar wheat fungicides are off-label. In fact, recent research presented at the 2017 Fusarium Head Blight meetings shows that in general, strobilurin products can actually increase the presence of deoxynivalenol (DON) in wheat if applied at full heading (Feekes 10 or 10.5). Thus, your better fungicide options for preventing scab are Caramba and Prosaro and these products can also kill any fungal diseases present on leaves (such as powdery mildew, tan spot, and rust). These products aren’t 100% for scab prevention due to the variation of heading and flowering that occurs in so many fields. Better efficacy is obtained with more uniform plants which begins at seeding time. So I would recommend watching the growth stage in your fields, the weather, and the prediction tool regarding if you feel you need to treat any fields this year to prevent scab. Research has shown best efficacy to be obtained when at least 50% of the plants are at 1/3 flowering. Flowering begins with yellow anther sacs in the middle of the head with flowering continuing throughout the head from there. Once the pollen is released, the anther sacs turn white.
LBNRD Open House Public Hearing: The Little Blue Natural Resources District (LBNRD) is hosting a public hearing on May 29th from 6:30-9:00 p.m. at the Davenport Community Center in Davenport, NE. The purpose of the hearing is to provide information and receive testimony on proposed amendments to Groundwater Management Rules and Regulations. The hearing will be an open house format allowing individuals to ask questions of the NRD staff, look at exhibits, and offer testimony. The proposed rule changes and additional information can be found on the LBNRD website at: http://www.littlebluenrd.org/. Please contact the NRD with any questions at (402) 364-2145.
Not part of my news column: on a more positive note after mentioning all the crop problems, the lilacs in general were beautiful and smelled amazing!!!
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!
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.
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.
Last week was a blur of phone calls but it’s great to receive them and know so many of you are doing your best to wait for your soil to be depleted before scheduling your first irrigation! There are some of you in the Little Blue NRD who haven’t received the rains the past few weeks and have hit the 90-100 trigger on your watermark sensors to schedule your first irrigation. Most of you reading this won’t have to irrigate till after tassel (and then you can take into account the 3rd foot in your average)! The 90-100 trigger relates to 35-40% soil moisture depletion and is proven by research via Dr. Suat Irmak at South Central Ag Lab for our silty clay soils. Waiting for the trigger, regardless if you’re on load control or not, will still allow you at least a week to 10 days before you have to worry about getting behind. Please continue to call with questions. There’s also a discussion topic on my blog for your comments/questions.
Corn and beans are looking good overall, are closing canopies, and corn is rapidly growing. Wheat is being combined in the southern tier of counties and there has been quite a range of yields due to the dry weather producing small heads and disease issues such as scab, smut, and ergot. Scab (Fusarium Head Blight) is a concern when we receive rain and high humidity during and around flowering. We were recommending fungicides at that time. Some people escaped it, some put the fungicide on, and others didn’t-so there’s a range of yields out there from that. Common bunt (stinking smut) is the smut that creates clouds of black spores when you’re combining and the grain smells like fish. Loose smut is loose in the head and doesn’t form a kernel shape like common bunt does. Both can be prevented by not saving contaminated seed and using fungicide seed treatments at planting.
Ergot is one I hadn’t seen in wheat since I’ve been here but have in roadside grasses. Ergot is caused by a fungus that infects the wheat head during cool, wet conditions during flowering. Like the fungus that causes scab, it simply replaces the normal pollination process and instead, a black/purple hard fruiting body (sclerotia) is eventually formed. Before this is formed, a sugary drop called honeydew is formed which then turns into the sclerotia. It’s a problem for our producers because I don’t know that you can set your fans to blow it out like you can for light, scabby kernels since ergot sclerotia are denser. The problem with ergot is that it contains toxic alkaloids (one is like LSD)…in fact, it’s blamed that ergot-contaminated grain is what caused the Salem Witch Trials. These alkaloids are also toxic to livestock so contaminated grain should not be fed or even blended off for livestock. Federal grain standards classify wheat as ergot infested when it contains more than 0.3% sclerotia. If you are finding ergot-contaminated grain in your fields, do not save seed back next year; start over with disease free certified seed. The sclerotia will live on top of the soil for a year (they will produce spores next growing season so don’t plant contaminated wheat fields back into wheat, barley, oats, or triticale). Mowing roadside ditches and keeping wheat fields free of other grasses can help prevent ergot infested grasses from spreading the ergot fungus to wheat via blowing spores and rain splash. More information can be found by checking out the UNL Extension publications Head, Grain, and Seed quality on the http://cropwatch.unl.edu/web/wheat/disease Web site.
The last week I have received questions about white heads in wheat. An excellent resource from UNL to determine various wheat head disorders can be found here. If the heads are completely bright white and you can easily pull those heads out of the stem, the culprit is the wheat stem maggot. This insect will sever the stem above the top node so that the stem upward to the head are white while the rest of the plant remains green. I usually only see a few of these types of heads scattered around in fields and there’s no recommendations for managing it because damage isn’t considered economical.
If your heads have white or pink colored kernels in them in addition to regular looking kernels, chances are the discolored kernels have Fusarium Head Blight also known as head scab. The kernels eventually may have a brown discoloration to them and the stem just below the head may also turn a brown-purple color. The Fusarium fungus that causes head scab is the same that causes stalk rot in corn. Wheat on corn rotations in no-till systems have a greater potential of scab in wheat, but these situations don’t mean that scab will always occur. Ultimately, rainy, humid conditions for a 2 week period around flowering is the primary factor for allowing scab to occur.
If you are finding scab in your fields, there’s nothing to spray or do now. Set your combine to blow out the lighter, shrunken, scabby kernels to help avoid dockage at the elevator. I would also recommend to avoid saving back scab-infested seed. Plan to purchase certified seed instead for next year and be sure to have a fungicide seed treatment applied to it to avoid problems with smut.