Zombie Weed Apocalypse

By: W Kevin Nelson, CCA 4R NMSSenior Agronomist, Prairie Agronomics, LLC 

The growing season of 2019 just keeps on giving. Without going over all the morbid details, let’s just say that it’s been challenging from the very beginning, and looks like the challenges will continue on through to harvest and beyond.

As we get into the latter part of summer we are still contending with weeds that have refused to die. For lack of a better term, zombie weeds. These weeds have had burndown herbicide treatments, pre-emergent residual treatments, one or more post treatments, and still refuse to die. Some are newly emerged, some have just not succumbed to the programs we had planned before the spring weather went off the tracks. And now they have gone to seed, or soon will.

At this point, another spray trip becomes little more than an attempt at revenge. The plants are way above label size restrictions, and have hardened off with the dry conditions of the last few weeks. The chances are they won’t die, and the seed on them is probably already viable to bring on the next generation.

Am I going to give you the solution to the zombie weed apocalypse? Probably not. But I’ll point out that this weed control disaster isn’t a failure in any one program or system. We can find fields under all types of management that is experiencing problems, owing mainly to the conditions of the growing season. What I will say is this: start right now addressing the weed problems that will probably be coming our way in 2020.

Since many, though not all, weed control systems now combine seed traits with herbicide products, now is the time to start putting those combinations together. These systems must start with variety and hybrid selection, and seed companies will be on your doorstep early this fall. Choose a system that fits your needs from a production standpoint as well as weed control ability.

Consider cover crops to suppress weeds this fall. Some cover crop mixtures are better than others at keeping weeds down, and the consideration on how to terminate these crops needs to be factored in. Seed supplies may be an issue, as well.

Talk to your retailer about a fall burndown treatment. This can make a tremendous difference in weed pressure in the spring. With what looks like an extended harvest, it is crucial that you make your plans and let your retailer know with plenty of time what you intend to do.

So as you look out over your fields, frustrated with the zombie weeds poking through your crops or covering your Prevented Planting acres, remember that they aren’t coming after your brains, but you will need to put your brain to work now to prepare to hold them in check in the coming seasons.

Using Dicamba this Growing Season

Last year we gained more experience than we wanted to have on evaluating dicamba damage in soybeans that were not traited for dicamba.  While I do not think that the new label requirements adequately address the volatilization issue, I think they will halp to deal with some of the issues people had with their dicamba applications. 

Dr. Aaron Hagar issued a new bulletin today on dicamba use that is worth a read, especially if yo uare using dicamba. 

Looking for Better Weed Control?

Weed Control has become the biggest field management issue of the decade.  Everyone seems to have troublesome weeds.  Finding the right herbicide, timing the application right, and getting good kills are important.

The best weed control I am seeing in soybeans right now is with cover crops and No-Till.  Cereal rye is the easiest cover crop to manage in soybean production.  You can plant it late after corn and let it grow or kill it early.  Some producers say it is easiest to plant  soybeans in green cereal rye and kill it just before or just after planting.

Narrowing your soybean rows to 15 inches or less can also help with weed control.  The past few years, we are seeing waterhemp growing in the middles of 30 inch row beans.  An early canopy is important for good weed control.

Notice I have not talked herbicide management yet.  If you are not using cover crops, start in the fall.  Fall herbicides can give you a jump on sporing weeds.  Soil applied herbicides in spring are important.  In spite of a lot of bad publicity, early dicamba can give good control of marestail.  Be cautious with later season dicamba operations.  Post planting applications should be done when weeds and crops are both small.  Don't rely on post applications for your whole program.

Prairie Farmer says to"Turn 2017 Observations into Better Weed Control."

Safe time to Spray Dicamba

After a number of inspections of dicamba affected fields, I can offer no good insights as to how to spray dicamba safely.  Prairie Farmer recently published and article on How to Hit Dicamba's Narrow Application Window.  Volitilization and re-volitilizatoin seem to be factors in many of the cases we have looked at.  Temperature inversions must be to blame.  It is easy enough to cover wind speed and buffers, but how do you avoid inversions that are not readily apparent at application time.  The Pocket Spray Smart App may be helpful according to the article above.  The app attempts to predict inversion conditions 72 hours out.  The label for new dicamba formulations are only approved for only one more year, so if you think we need this tool in the weed control box, we need to do a lot better next year.

Dicamba Research Issues Starting to Surface

After many weeks in the denial and back steppping mode by the manufacturers of the new formulations of dicamba, we seem to be getting some information that perhaps Monsanto, BASF and DuPont need to take another look at what they did wrong.  First it looks like they hid behind the veil of corporate secrecy to get their label approvals. It also looks like there was little field testing of the products.  It looked good on paper so lets run with it.  Check out the RPM Soils Facebook Page for links with all the details.  We have been posting there.

Palmer Amaranth Control with Dicamba

Reports out of Western Tennessee show spotty results with Dicamba on Palmer Amaranth.  Results are discussed in No-Till Farmer. If you do not get a complete kill follow up with other treatments.  A hoe may be the only effective one.

Dicamba Use in Soybeans

Last week Dr. Hager discussed the use of Dicamba with Xtend soybeans.  He cautioned that the Dicamba will not be a silver bullet, but it may be a good tool in the toolbox if used properly.  He says Dicamba was never rated excellent on Water Hemp, but it is very good for now.  You should use the Dicamba according to its very restrictive label.  Beware of too much and too little wind.  There is only one approved nozzle.  If you mess anything up you could be in violation of label restrictions.  More on Dicamba Stewardship.

Weed Control

Last week we attended the Illinois Crop Management program in Springfield.  They seemed to save the best speaker for last.  Dr. Hager discussed weed control in the resistance era.  He continues to call for multiple modes of action in the same application.  He showed us why herbicide rotations are not really effective in keeping resistance at bay.  His discussion of Palmer Amaranth took up a big part of the program.  He says we need to have zero tolerance.  That means if soybeans are too tangled to walk through, you need to get in the truck or 4 wheeler and go get the plants.  The destruction of crop will be minor in comparison to the problems created by the Palmer amaranth.  Evena few weeds should be removed.  More on resistance here.

More Fall Weed Control

My advice would be to start your weed control program for next year now.  Aaron Hagar offers fall weed control advice in this Bulletin.

Fall Weed Control

I have written several times on fall weed  control.  Early on, I failed to see the value.  With resistant weeds and heavy pressure, fall weed control is making sense to me at this point.  One fall weed control technique is to use fall applied herbicide.  A residual herbicide will not only supress the winter annuals, but i will also give some early spring control.  Use herbicides if you have n ot planned on cover crops.

The second technique of course it to use cover crops.  Weed suppression will last well into the growing season, and I have seen very good results.  You may still be able to get cereal rye seed to sow on fields that are going to soybeans next spring.  If this is your first time to use cover crops, I do not recommend planting corn into cereal rye.  I have one customer who is planning to do so, but he has done a lot of research on the subject before taking the plunge.

No-till Farmer says Weed Control and Soil Health go Hand in Hand.  

Herbicides and Cover Crops

Cover Crops are a great way to improve your soil health and enhance your weed control.  Issues with using cover crops include the ability to plant them in a timely manner and the ability to get a reasonable stand.  One of the factors standing in the way of a good stand is what residual herbicide have you used on the current crop.  No-till Farmer writes about Corn and Soybean Herbicides and Rotation to Cover Crops .  They say that for most herbicides, you should not have a problem.

Sources of Palmer Amaranth in the Midwest

It is a really bad year for Waterhemp in our area.  Palmer Amaranth is closely related, and vigilance is needed to keep it under control.  Beware of sources that may bring seeds to your area.  I have seen Palmer Amaranth in Bond County that came in Cottonseed dairy feed products.  The seed runs through the cow and you spread it on your fields.  Another source may be CRP seed.  This article out of Ohio from No-Till Farmer suggests screening CRP mixes to get rid of Palmer Amaranth. I have heard reports of dirty seed out of Iowa as well.  Also, be sure clean harvest equipment when moving from infested fields.  University of Arkansas is suggesting the only way to control Palmer Amaranth is total eradication.

Weedy Soybeans

Lots of soybeans are getting weedy.  I am not sure of herbicide program in these fields, but the bottom two fields missed the mark.  The top photo shows fairly clean beans.  Only a few stalks of corn are poking through.  The beans in the middle photo look pretty good over all , but there was a conspicuous gap in spray coverage.  The bottom photo shows a field where late season weed control is not good.  Last week on the way to Kentucky, I noticed weeds especially bad in the middles of 30 inch rows.  I could not find that today. Probably 80 to 90% of the weeds are waterhemp.

Fairly clean

Sprayer Gap in  the Middle

Weedy

Sprayer Skip

Not all sprayer mistakes are this easy to see.  This field had several gaps.  If it was custom applied, I would invite them back at their cost.

Sprayer Skip