Category Archives: Trees

JenREES 6-17-18

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/.

Emerald Ash Borer

emerald ash borer

Bagworms in Evergreens

I’ve been receiving questions regarding when to spray for bagworms. Bagworms overwinter as eggs in these up to 2″ bags which are formed throughout the summer with silk and evergreen needles by larvae. Larvae feed until late August or early September. Males then emerge and mate with females through the bag opening in September. 500-1000 eggs are deposited by female moths within their own bags.  After depositing eggs, the females drop to the soil and die.  Bagworms overwinter as eggs within bags fastened to twigs such as these shown in this photo.

Bagworms

Eggs hatch in mid-May to early June. Some caterpillar larvae remain on the same trees containing the bags from which they hatched.  Others are blown by the wind to area trees allowing for new infestations to occur.  This photo shows new bags (1/8-1/4″) being formed on trees as they create these bags around themselves.  Look closely for these tiny bags on trees right now.  The video below shows how to look for bagworms on evergreen trees right now.  Study your trees and look for small movements on small bags being formed.  If you are seeing this, consider treating your trees for bagworms.  Products containing bifenthrin or permethrin irritate caterpillar larvae causing them to come out of the bags and be exposed to the pesticide.  There are a number of other management options available.  Please see the following publication for more information.   

Nebraska Extension Publication:  Bagworms

Treating Iron Chlorosis in Trees

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Throughout the County, iron chlorosis is appearing in trees and landscapes. It can especially be seen in the silver maples (shown in this photo) and pin oaks. Iron chlorosis symptoms appear as yellowing of leaves while the leaf veins remain a dark green color. Eventually the leaves become so chlorotic that leaf tissue begins to turn brown/black and die. Severely affected leaves often drop from the tree and new leaves emerge in 7-14 days. Alkaline soils (pH above 7) reduce the availability of iron and manganese; two important nutrients found in tree leaves. It’s not necessarily that these nutrients are deficient in the soil. The high pH just makes these nutrients less soluble and unavailable to the trees. Adding iron to the trees or the landscape around the trees won’t correct the problem as the pH ultimately needs to be corrected.

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.

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I learned of another potential method to consider from John Fech, Extension Educator in Douglass/Sarpy Counties, and we tried it at the Sutton Cemetery for two years and at the Clay County Courthouse last year with decent results. The first step is to double aerate the area from the trunk to the dripline of the trees showing iron chlorosis symptoms. The dripline is the outer leaves of tree. Do so several days after irrigation/rainfall to avoid tearing up the grass in your lawn. Often people aerate their lawn in the spring and/or fall, so if you have a problem with iron chlorosis, you could include the following treatment into your routine.

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The second step is to broadcast spread granular sulfur on the soil surface. Then broadcast spread iron sulfate on the soil surface. What was recommended to us by Omaha Master Gardeners was using 3 lbs of sulfur + 3 lbs of iron sulfate for “small” or newly established trees; 4 lbs of sulfur + 4 lbs of iron sulfate for “medium” sized trees; and 5 lbs of sulfur + 5 lbs of iron sulfate for “large” established trees. I realize that’s not very scientific based on sizes so do the best estimation of tree size that you have. We used 5 lbs for everything at the cemetery and courthouse. Here Mike, Clay County Courthouse Custodian, is spreading the product close to the trunk first.

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He continued applying around the tree in a circle gradually moving out towards the drip line.  The final step is to then water the lawn.

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We have numerous silver maples at the courthouse. This is a photo of one of the trees and a close up of these leaves was shown in the first photo. You can see the yellow cast to this tree in this photo and how severely affected many of the leaves were from the first photo.

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This is the same tree a year later from the opposite side. The photo doesn’t do it justice as it truly is greener than last year and the leaves are hailed damaged. It didn’t really change during the season last year but all the courthouse trees are greener this year. They could use another application though as they still show symptoms of iron chlorosis. This method may take several years before the soil pH changes enough for symptoms to disappear.

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.

Proper Tree Pruning

Special thanks to Dr. Scott Dewald for the wonderful evening of information he provided at our tree care workshop last week!

Scott Dewald explaining what to look for when considering pruning a tree.

Scott Dewald explaining what to look for when considering pruning a tree.  Scott shared that one should never prune more than 1/3 the height of a tree in one season.  Pruning should also be done to obtain a main leader and overall structure.  It’s also best not to prune limbs more than 2″ in diameter.  If the limb needs to be pruned but it encompasses more than 1/3 of the limit of what should be removed in a season, one could “head” the limb by removing a portion of it one year and then complete the cut the following year.  This will slow the growth of that limb.  

Scott Dewald showing workshop attendees where the bark collar ridge occurs on this branch.

Pruning cuts should always be made at the “bark collar ridge” which produces a round cut and allows the tree to naturally heal.  Scott shows attendees where the bark collar ridge is on this branch. 

Pruning Fact Sheet ENH847 from University of Florida Extension written by Edward Gilman.

Pruning Fact Sheet ENH847 from University of Florida Extension written by Edward Gilman with good visuals of where proper pruning cuts should occur.

Workshop attendee demonstrating "heading" of a branch.

We learned that on large branches, it’s good to make a cut farther out to remove the weight first, and then go back and make the proper cut at the bark collar ridge.  Improper pruning can result in further damage to the tree.  Here we were trying to correct this tree for not having a main leader.  Typically one would leave the southern-most branch according to Scott, but in this case, the northern-most branch was stronger.  Scott said there was no need to stake the tree or try to get the northern-most branch to straighten out as it would naturally do this in time on its own.

This attendee is now making the proper cut at the bark collar ridge.

After a large part of the branch weight has been removed, this attendee is now making the proper cut at the bark collar ridge.  

Additional Problem-Planting too shallow.

We also walked from tree to tree in the park looking at additional problems.  I noticed how high the mulch was piled on some of the trees.  Mulch should never be placed against the base of the tree as it can cause rot.  But in this case, it was observed that the person who planted the tree did not dig a deep enough hole.  What appeared to be a pile of mulch was the actual root ball and soil mounded up above ground.  

Additional problem with this tree.

This situation also most likely was a result of improper planting.  In this case, the tree roots began wrapping around the base of the tree girdling it (like choking it).  

Weed wacking

This is the most common problem I see with tree calls.  A huge enemy to trees are weed whackers!  In this case, you can see extensive damage to the bark  and the base of this tree.  Depending on the damage and how well the tree can seal the wound will depend on if the tree will survive or not.  Often, as in the case of this tree, the tree will be weakened with few leaves appearing on branches.  It’s best to place mulch around trees in order to avoid having to use weed whackers on them-but again, don’t place the mulch up against the base of the tree!

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!

Tree Care Workshop

TreeCareWorkshop

The Memorial Day and August 1st storms of 2013 did significant damage to our trees in Clay County. This workshop is designed to provide demonstrations on pruning techniques, what to look for, and learning how care for your storm damaged trees in future years. There is no charge and all are invited to attend. Please spread the word as many trees were damaged last year!

October Landscape Projects

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.

Water

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 lawnsWatering bushes in the fall. 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.

Planting

Because roots continue to grow well into fall, September through October is a good time to plant deciduous trees and shrubs. For spring flowering Tulips along the side of our house.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.

Weed Control

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!

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.

Evergreen Tree Diseases

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 1 Flowers-No Fooling!

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!

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