Category Archives: Trees
This past week contained many off-target herbicide concern calls. Prior to Memorial Day I had made a note that post-herbicide applications to corn began in much of the area and anticipated phone calls to begin in about two weeks. Most of the conversations this week were more FYI to let me know they had soybean leaf cupping.
Here’s a few things to consider if you are having soybean leaf cupping.
- First, was a post-herbicide application made to your soybeans? If so, check for any potential tank contamination (Check out this CropWatch article: https://go.unl.edu/fnig). If not, check out this publication (http://ipcm.wisc.edu/download/pubsPM/dicamba2004.pdf) to determine if any of the criteria mentioned could possibly be contributing to the problem.
- Determine how old the plant is by asking when the soybean was planted and even better when it emerged. A soybean plant will produce a new node every 3.75 days.
- To determine the timing of damage, I count the total number of nodes on the plant to the last trifoliolate where leaf edges are not touching. The total number of nodes may differ in different parts of the field such as irrigated and non-irrigated especially after herbicide damage and drought-stress (Example 8 nodes irrigated and 6 non-irrigated). Take the number of nodes X 3.75 to get total approximation of plant age. Then count back on the calendar to determine approximate emergence date. If I use 8 nodes in this example X 3.75 = around 30 days ago the plant emerged.
- I then count the number of nodes to the very first damage I see on leaves (Example 3). Multiply this number of nodes times 3.75 and count forward on the calendar from emergence to that date. For instance, in this case, damage occurred around 11 days after emergence.
- I also like to count how many completely unfurled trifoliolates are affected (Example 6 trifoliolates). Take that number and multiply by 3.75 (Example 6 X 3.75= approximately 23 days ago the damage occurred).
- In this example, it worked to count either direction (from emergence and from current date) to determine approximate timing of off-target movement occurring. In all the situations I’ve looked at thus far, the timing goes back to around Memorial Day with post-dicamba herbicide applications applied to corn.
- Auxin-like herbicides affect only cell division. Thus, fully developed leaves (no longer expanding via cell division) are not affected even though they may be expanding by leaf cell enlargement. Only the tips of the newest exposed soybean leaves may experience damage to dicamba as they are still undergoing cell division. Otherwise, it can take 7-14 days for leaf damage from dicamba injury to appear on susceptible plants and damage will occur typically 4-6 nodes. This is because dicamba is also translocated once inside leaf cells. Thus it impacts cell division of the leaf primordia at the stem apex. We may not even see those leaves yet because they are still enclosed in the stem apex tissue.
- In a matter of weeks, affected fields can go from appearing to have minor damage, to looking really bad, to growing out of damage. It looks worst when those affected nodes push upward giving the field a grayish/white cast to it as the leaves become much reduced in size and are tightly cupped. Eventually the leaves will begin to look more normal again in time (as long as a second off-target movement doesn’t occur).
What can you do? Water via irrigation and/or rainfall is the best recovery tool for dicamba damage. Waiting is another. We’re blessed to grow indeterminate soybean in Nebraska which continues to produce nodes and leaves upon flowering which allows our soybean to grow out of damage.
- Wait till harvest to determine any yield impacts if there are areas impacted vs. those which aren’t. Otherwise, field-scale damage is difficult to discern yield impacts.
- You can talk with your neighbors/ag retailers regarding what they sprayed. In our area of the State, it’s often difficult to pinpoint the source of off-target movement with so many applying dicamba products to corn for palmer control often around the same time-frame. Now that post-apps to soybean are also occurring, that may also become a challenge. Of all the fields I visited last year, less than a handful of farmers sought any sort of compensation and those were more often due to tank contamination issues. If you wish to pursue that route, you need to file a complaint with the Nebraska Department of Ag.
- For future dicamba applications, check out these best management tips: https://go.unl.edu/97ok.
- For those of you reading this in a source outside of my blog, I created a video to hopefully be more visual and clear on understanding this method of diagnosing timing. You can check it out at my YouTube site: https://www.youtube.com/user/jenreesources.
Bagworms: It’s June and one of my top questions has been “Have I found bagworms yet?” Well, they’re now feeding and forming new bags on junipers and spruces. What you’re looking for are not the old bags at this point, but very small (fingernail size) new bags that move as the caterpillar is feeding and making the larger bag. This video from Backyard Farmer (https://youtu.be/05A2quj9nO4) does a great job of showing various stages of bagworms and sharing on control methods. Check it out!
Irrigation Scheduling Workshops: Steve Melvin, Extension Educator in Hamilton/Merrick Counties asked I share about upcoming irrigation workshops hosted by UNL and Upper Big Blue NRD. The program will focus on installing the equipment and making irrigation scheduling decisions using the data generated by Watermark sensors. The workshops will be held from Noon-1:30 p.m. on June 25th at the Corner Café, 221 Main St in Stromsburg and also at the same time June 28th at the Hordville Community Building, 110 Main St. The Upper Big Blue NRD will provide the lunch. The first presentation will be Installation of Watermark Sensors and Data Logger presented by Dan Leininger, Water Conservationist with the Upper Big Blue NRD. The second will be Deciding When and How Much Water to Apply Using Watermark Sensor Readings presented by Steve Melvin. The irrigation scheduling strategies presented in Steve’s presentation can be used with any soil water monitoring equipment data. More information is available by calling Steve Melvin at (308) 946-3843 or visiting https://extension.unl.edu/statewide/merrick/.
Early in my Extension career, I inherited the job of injecting trees with a solution of iron sulfate. There would often be a waiting list of people to help, particularly in Sutton, when they’d see the jugs hanging from trees. As a plant pathologist, I was concerned about how much damage we were doing to the trees with repeated injections every five years or so…if secondary pathogens would affect these areas we were drilling in the trees. I was also concerned about providing a free service that took a great deal of time and if we were competing with industry by doing so. Eventually we stopped providing the service but we do rent out the equipment and can provide the recommendations on how much iron sulfate to add based on tree diameter if you are interested. But you may be interested in another less invasive method instead.
You most likely will not see any changes the first year, although the grass under the tree may appear greener. The goal is to change the soil pH to make the iron more available to the tree in the future. This may be a process that needs repeated for several years in a row and while it doesn’t show instantaneous results, it will most likely aid in the longevity of your trees by reducing the symptoms without additional harm to the tree through injections.
Special thanks to Dr. Scott Dewald for the wonderful evening of information he provided at our tree care workshop last week!
This was a fun workshop for me with the right size of group and great hands-on demonstration where we also learned from pruning mistakes and how best to correct them. Thanks again Scott!
In the landscape, October is the month to water, control weeds, and plant bulbs, trees and shrubs. It is also the month to wait until after a freeze to cut back perennial plants and wait for the soil to freeze before covering tender plants with winter mulch. Kelly Feehan, UNL Extension Educator, provides the following information.
Sometimes people ask if trees and shrubs should be watered at this time of year since their leaves will soon drop off; and how late in the season lawns should be watered. As long as the soil is dry, go ahead and water. Plant roots continue to grow long after leaves drop off trees and shrubs and after grass stops growing. Roots, rhizomes and stolons can grow well into November and fall watering promotes this growth helping plants recover from summer stresses. Plant energy can be used for root growth during fall since energy is no longer needed for leaves, flowering or seed production. Roots continue to grow until soil temperatures drop below 40 degrees Fahrenheit with available moisture.
Water enough to moisten the soil to a depth of about eight to twelve inches for trees and shrubs and six inches for lawns. Keep in mind that a lack of oxygen due to a saturated soil is just as damaging to roots as a lack of water. Allow the soil to dry between watering.
Because roots continue to grow well into fall, September through October is a good time to plant deciduous trees and shrubs. For spring flowering bulbs, wait until soil temperatures drop to 60 degrees Fahrenheit to plant.
A common question asked about fall planting is if a starter fertilizer needs to be used at planting time. Starter fertilizers are high in phosphorous, a nutrient important to root production. The only way to know the answer to this question is to have a soil test taken. However, most landscape soils are high in phosphorous (P). Fall soils are often warm and dry which makes P more readily available. In most cases a starter fertilizer does not need to be used during fall planting.
More important is to plant at the correct depth. With bulbs, follow label directions for planting depth. It varies depending on bulb size. Some recommendations say to plant about one to two inches deeper than recommended. The opposite is true for trees and shrubs. Before planting trees, locate where the trunk flares out at the trunk base then plant at a depth so the flare is visible above ground. Do not loosen the soil beneath the root ball or the tree may settle and end up planted too deep. In heavier clay soils plant so the trunk taper is one to two inches above the ground.
October is the best time to control perennial broadleaf weeds like dandelions, ground ivy and clover. There is no ideal time during fall to apply lawn weed and feed products together. The best time to fall fertilize lawns is in early September and again in late October or early November. The best time to apply herbicides for lawn weeds is about mid-October before a hard freeze.
Weed control can be more effective and less herbicide will be applied where it is not needed by avoiding the use of combined weed and feed products during fall. One can achieve better weed coverage and control of established broadleaf weeds if the weeds are spot treated, typically with a liquid formulation of herbicide.
Here’s wishing you a great October of accomplishing landscaping projects!
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.
Somehow April flew by without me reminding you to apply fungicide sprays to Austrian and Ponderosa pines that have had problems with Sphaeropsis tip blight in the past. I’ve also received several scotch pine samples in the office to diagnose for pine wilt nematode. While there is no cure for pine wilt, I recommend to take a 6” long, 1-2” diameter sample of a dead branch to your local Extension office for diagnosis before cutting down the tree. Pine wilt affects Austrian (long needles groups of 2) and Scotch pines (short needles in groups of 2) as they are non-native trees while the nematode is native. Since ponderosa pines (long needles in groups of 2 and 3) are native to Nebraska, they don’t seem to be affected by pine wilt nematode.
Pine wilt is caused by beetles carrying pine wood nematodes vomiting them into the water-carrying vessels of the tree (xylem). The tree senses the nematodes and essentially blocks water to those branches. Often you will observe a branch then perhaps a side of the tree and eventually complete death of the tree within 6-9 months. While I have diagnosed many samples of pine wilt, more often when I visit homeowners the tree problems are due to fungal diseases which occur on the needles. If you look closely at your needles and observe dark bands or rings on them followed by death of the needle either direction from the band, the tree problem is most likely due to a fungal needle blight like dothistroma in Austrian and Ponderosa pines or brown spot in Scotch pines. They can all be prevented by spraying a fungicide containing copper sulfate in the spring.
With everything about 3 weeks early this year, now is the time to spray Ponderosa and Austrian pines for needle blight and spruce trees that have had problems with needle cast or shoot blight where the new growth has died in the past. In early June spray for needle blight problems in Scotch pine and cercospora blight on cedars. If you have a windbreak of combinations of these trees and don’t want to spray twice, I recommend at least spraying in early June to catch all of them. Increasing air flow by cutting out some trees is another way to reduce fungal diseases on your trees.
Also watch trees for bagworms as you may be able to tank mix a fungicide/insecticide application in early June if needed. We would recommend picking the bags off trees and burning them, but that’s just not feasible in windbreak situations. To know when to spray, take a few of the bags off the tree, place them into a plastic ziplock bag, and place outside on the south side of your house. When the larvae emerge from the bags, check your trees to see if larvae can also be observed on them. Pyrethroid insecticides are recommended for managing bagworms because they cause an irritation that makes the larvae leave the bags and allow them to be exposed to the pesticide.
Great brochure! Evergreen Diseases
April 1st, while typically a day of pranks and jokes, has one obvious truth. Spring has arrived in full force with flowering plants at least 2-3 weeks earlier than normal. I couldn’t believe that my lilacs, which typically bloom around mid-May were blooming for the first time today! I planted many of the bulbs and shrubs last fall and have been rewarded with beauty, color, and lovely smells via God’s creation this spring; enjoy the pics!