Source: David Marrison, Coshocton County Extension Educator
When the news broke that we would need to retreat to our homes due to Coronavirus-19, the run on milk, eggs, bread and toilet paper began at our local grocery stores. I have been especially fascinated by the hoarding of toilet paper. Every time I have been out to get food and supplies, the toilet paper shelves have been completely bare.
As my wife Emily and I were out taking a Sunday evening walk, I noticed along the ditches some green, soft-looking plants which appeared to be the lambs-ear plant, with which many of us are familiar. After closer inspection, the plant we were looking at was Common mullein or Verbascum thapsus. Emily was quick to respond that locals refer to the plant as Cowboy’s Toilet Paper. Then the light bulb went off—could this be Mother Nature’s answer to our COVID-19 toilet paper shortage?
Besides Cowboy’s Toilet Paper, you may have heard it referred to as Quaker’s rouge, candle wick, flannel leaf, velvet dock, big taper, bunny’s ear, miner’s candle, or poor man’s blanket. These names commonly reflect some characteristic the plant exhibits, such as the flower stalk or leaf texture. If you read survival guides, this plant is mentioned as an emergency roadside toilet paper due to the large, fuzzy leaf of this botanical wonder. One word of caution however, the fuzzy leaf may cause some skin irritation when used as toilet paper.
The history of this plant is fascinating. Common mullein traces its roots back to Europe as it was planted in gardens for its medicinal purposes as an expectorant, diuretic, pain relief and healing of abrasions. Interesting enough, since Quaker women weren’t allowed to wear make-up, they would rub the hairy leaves on their cheeks to create a homemade blush look. Hence the name Quaker’s Rouge. However, its major claim to fame is definitely its use as a toilet paper.
According to our network of sources, the effectiveness of new soybean trait systems has some growers once again thinking about omitting preemergence residual herbicides from their weed management programs. Some people apparently need to learn the same lessons over and over again. Having gone through this once in the early 2000’s when Roundup Ready soybeans had taken over and we all sprayed only glyphosate all day every day, we think we’re pretty sure where it leads. We’re sensitive to concerns about the cost of production, but the cost-benefit analysis for residual herbicides is way in the positive column. We’re not the ones who ultimately have to convince growers to keep using residual herbicides, and we respect those of you who do have to fight this battle. Back in the first round of this when we were advocating for use of residuals, while the developers of RR soybeans were undermining us and telling everyone that residuals would reduce yield etc, we used to have people tell us “My agronomist/salesman is recommending that I use residuals, but I think he/she is just trying to get more money out of me”. Our response at that time of course was “no pretty sure he/she is just trying save your **** and make sure you control your weeds so that your whole farm isn’t one big infestation of glyphosate-resistant marestail.” And that answer probably works today too – maybe substituting waterhemp for marestail.
We need to state here that a good number of growers kept residual herbicides in their programs through all of this, and we assume they aren’t tempted to omit them now either. For everyone else – maybe interventions are called for. Where the recalcitrant person is repeatedly thumped with a stick while being reminded of what happened last time, until they change their minds.
Weed scientist: so you’re going to use residual herbicides right?
Soybean grower: no
WS: remember what happened last time – lambsquarters became a problem when every residual herbicide would have controlled it. Change your mind yet?
WS: remember when the weather didn’t cooperate and you ended up spraying 2 foot tall weeds because of no initial control? Do you want this again?
WS: so you’re going to use residuals?
SG: not sure
WS: and you expect your local dealer to clean up whatever mess occurs when you don’t use residuals?
WS: remember when you burnt out the FirstRate on marestail and then the glyphosate wouldn’t work? Do you want this to happen with dicamba, 2,4-D and glufosinate?”
WS: well then
Gentler persuasive tap
WS: You know how bad a weed waterhemp is right?
WS: what if residuals will help prevent waterhemp infestations
SG: Ok then – yes
WS: ok then
Note: we considered a number of sound effects here – thump, zap, whack…. Thump won out for no particular reason. We could not decide whether getting hit by a stick was more or less acceptable than getting shocked in this context.
The bottom line is that residual herbicides provide both short- and long-term risk management in weed management for a relatively low cost. A non-inclusive list of these:
– reduces weed populations overall and slows weed growth, resulting in more flexibility in the POST application window.
– Reduced risk of yield loss if weather interferes with timely POST application. In the absence of residual herbicides, soybean yield loss can occur when weeds reach a height of 6 inches.
– increases the number of different sites of action used within a season, slowing the rate of resistance development
– reduces the number of weeds that are treated by POST herbicides, which also slows the rate of herbicide resistance development
– residuals control lambsquarters which is not well-controlled by POST herbicides
– the most significant weed problems in Ohio soybean production – waterhemp, giant ragweed, and marestail – cannot be consistently controlled with POST herbicides alone. They require a comprehensive herbicide program that includes residual and POST herbicides. It may be possible to make a total POST system work some years or for a while, but in the end this approach will result in problems with control and speed up the development of resistance.
This whole subject of omitting residual herbicides makes us cranky because we don’t have to guess what will happen. We’ve made our best case here. It’s up to you of course, but we suggest that we not have to come back and have this discussion again. Because next time we’re bringing a few friends, a bigger stick, and a gorilla.
Disclaimer: Parts of this article are meant in pure jest. We would certainly never advocate in earnest the use of physical harm or other methods of persuasion to change the behavior of herbicide users. This goes against everything that the discipline of weed science stands for, and also OSU. Plus – we don’t even know where to rent a gorilla.
If you have never applied herbicide in fall to burn down winter annuals, or done it only infrequently, this might be the year to make an investment in fall herbicides. Fall treatments are an integral component of marestail management programs. They also prevent problems with dense mats of winter annuals in the spring, which can prevent soil from drying out and warming up, interfere with tillage and planting, and harbor insects and soybean cyst nematode. 2019 was a generally tough year for weed control, leading to higher end of season weed populations in some fields. A number of acres were never planted, and growers got to experience the difficulty in obtaining season-long control in the absence of a crop. Reminds us all how important the crop canopy and shading of the soil is during the second half of the season. Bottom line – there was substantial production of weed seed in some fields, and a replenishment of the soil seedbank by both winter annual and summer annual weeds. The seed of winter annuals and marestail lacks dormancy so above-average weed seed production can lead to an immediate increase in fall-emerging weeds. Applying herbicides this fall can compensate for increased weed populations and make life easier in the spring.
We have published information on fall herbicides fairly frequently, and our suggestions for fall treatments have not really changed much. There is plenty of information on fall herbicide treatments in the C.O.R.N. newsletter archive and on other university websites. Our philosophy on this has not changed much over the past decade. A few brief reminders follow:
1. When to spray? Anytime between now and Thanksgiving will work, and possibly later. We have applied into late December and still eventually controlled the weeds present at time of application. Once hard freezes start to occur, there is usually a substantial change in the condition of certain weeds, such as dandelion and thistle, that renders them less sensitive to herbicides. We discourage applications during periods of very cold weather which can occur starting about Thanksgiving, and also (obviously) when the ground is snow-covered. The generally dry conditions we are experiencing have limited weed emergence so far this fall. We anticipate that rain occurring now that leads to some sustained soil moisture near the surface will likely result in germination and emergence of the weeds that have been missing until now. Our recommendation is to wait for rain and the additional weed emergence before applying any herbicide this fall. The risk in this is that the weather turns wet, making it difficult to apply herbicide. So it’s also possible to apply now and include a residual component to help with later fall emergence (which is the exception to the “no residual” recommendation in #4 below), such as simazine, a low rate of metribuzin or Canopy, or a Sharpen rate higher than 1 oz.
2. What about all of the crop residue on the ground after harvest – won’t that cause problems? We have not worried about this, and the herbicides seem to work regardless. Most agronomists I have asked have the same impression. On the other hand, it probably wouldn’t hurt to wait a while after harvest to let the residue settle down, and the weeds to poke through. Dense crop residue usually prevents marestail from emerging anyway. Continue reading →
The world of soybean herbicide resistance traits has gotten more complex over the past several years. The good news is that we have new options for control of herbicide-resistant weeds, although it can be a little difficult to sort out which one is best for a given situation and whether the possible downsides of certain traits are tolerable. The following is a quick rundown of what’s available and some things to consider when selecting seed. This is not meant to be an extensive evaluation/description of these systems because including all the possible configurations of herbicide use and the stewardship stuff would probably kill the possibility that anyone reads the rest of the article. We also do not attempt to include all of the possible seed trade names. For ratings of herbicide effectiveness on certain weeds, check the tables in the “Weed Control Guide for Ohio, Indiana, and Illinois”.
Roundup Ready (RR1, RR 2 Yield, etc.) – the original herbicide resistance trait. Resistant to glyphosate which can be applied anytime up through R2
LibertyLink – resistant to glufosinate (Liberty, Interline, etc.) which can be applied anytime up to R1.
LL-GT27 (Freedom Plus, etc.) – resistant to glyphosate, glufosinate, and isoxaflutole (Balance), although there is currently no isoxaflutole product approved for use in these soybeans.
Enlist – resistant to glyphosate, glufosinate, and 2,4-D. Enlist One (2,4-D choline) and Enlist Duo (2,4-D choline + glyphosate) are the only 2,4-D products approved for preemergence and postemergence use on this soybean, outside of the typical use of 2,4-D ester 7 or more days ahead of planting that works on any soybean. These products can be used any time before or after planting Enlist soybeans without a waiting period as well as postemergence through R2
Roundup Ready Xtend – resistant to glyphosate and dicamba. XtendiMax, FeXapan, and Engenia are the dicamba products approved for preemergence and postemergence use on this soybean. These products can be applied any time before or after Xtend soybean planting without a waiting period, as well as postemergence (prior to R1 and no later than 45 days after planting).
Note: Dicamba and 2,4-D are different herbicides. Dicamba cannot be applied to Enlist soybeans and 2,4-D cannot be applied to Xtend soybeans. Just like glyphosate cannot be applied to LibertyLink soybeans and glufosinate cannot be applied to Roundup Ready soybeans. Seems obvious but it’s a surprisingly frequent question.
All of these soybean herbicide trait systems have utility in certain situations. Factors determining this are the resistant weeds present and the type of tillage. The primary resistant weed issues in Ohio, which require herbicides other than glyphosate, are marestail, giant and common ragweed, waterhemp, and Palmer amaranth. A few things to consider here – all of which assume that some type of residual herbicides are being used, regardless of the specific weed issues: Continue reading →
Information on preharvest herbicide treatments for field corn and soybeans can be found in the “Weed Control Guide for Ohio, Indiana, and Illinois”, at the end of these crop sections (pages 74 and 141 of the 2019 edition). Products labeled for corn include Aim, glyphosate, and paraquat. Products listed in the guide for soybeans include Aim, paraquat, glyphosate, and Sharpen. Some dicamba products are also approved for preharvest use in all types of soybeans, which escaped our notice until now, so it is not listed in the guide. The basic information for preharvest dicamba (for 4 lb./gal products):
Apply 8 – 32 oz/A as a broadcast or spot treatment after soybean pods have reached mature brown color and at least 75% leaf drop has occurred; soybeans may be harvested 14 days or more after a pre-harvest application; do not use preharvest-treated soybean for seed unless a germination test is performed on the seed with an acceptable result of 95% germination or better; do not feed soybean fodder or hay following a preharvest application of this product.
Preharvest herbicide treatments are primarily intended to suppress/kill and desiccate weeds that can make harvest more difficult. Products with contact activity will cause faster desiccation and leaf drop of weeds but may be less effective at killing weeds compared with systemic products. Effective desiccation with contact herbicides may still require a week or more following application. Differences can vary by weed. The maximum paraquat rate is well below the rate required to actually kill large weeds, but it is still probably most effective for desiccation of morninglory. Glyphosate is not likely to be effective on marestail and waterhemp, and many giant ragweed populations, whereas dicamba may with enough time between application and harvest. The first frost will usually provide the same results, so in a situation where crop maturity is delayed as is the case in many fields this year, consider whether an herbicide treatment is actually needed.
Preharvest treatments are not intended to be used to speed up crop maturity, and largely do not accomplish this. The restrictions on preharvest treatments that specify how mature the crop must be at time of application are designed to minimize any effect of herbicides on crop maturation. Applying earlier than specified could interfere with that process. The residue tolerances for this use are also based on a certain application timing, and failure to follow label guidelines could result in illegal herbicide residues in grain.
Remain vigilant! We have Palmer and Waterhemp in Knox County!! Now is an excellent time to scout for these weeds, especially in bean fields. If you would like help with identification call John at 740-397-0401.
If you don’t already have to deal with waterhemp or Palmer amaranth, you don’t want it. Ask anyone who does. Neither one of these weeds is easy to manage, and both can cause substantial increases in the cost of herbicide programs, which have to be constantly changed to account for the multiple resistance that will develop over time (not “can”, “will”). The trend across the country is for Palmer and waterhemp to develop resistance to any new herbicide sites of action that are used in POST treatments within about three cycles of use. Preventing new infestations of these weeds should be of high priority for Ohio growers. When not adequately controlled, Palmer amaranth can take over a field faster than any other annual weed we deal with, and waterhemp is a close second. Taking the time to find and remove any Palmer and waterhemp plants from fields in late-season before they produce seed will go a long way toward maintaining the profitability of Ohio farm operations. There is information on Palmer amaranth and waterhemp identification on most university websites, including ours – u.osu.edu/osuweeds/ (go to “weeds” and then “Palmer amaranth”). An excellent brief video on identification can be found there, along with an ID fact sheet. The dead giveaway for Palmer amaranth as we move into late summer is the long seedhead, and those on female seed-bearing plants are extremely rough to the touch. We recommend the following as we progress from now through crop harvest: Continue reading →
Source: Christy Sprague, Michigan State University
The challenging conditions this spring have left many fields unplanted. Glyphosate- and multiple-resistant horseweed (marestail) dominates a majority of these fields. Horseweed and other weeds in these unplanted fields need to be controlled prior to setting seed to prevent future weed problems. To help determine some of the more effective options for horseweed control, we sprayed several treatments two weeks ago on 2 feet tall horseweed. Common lambsquarters, common ragweed and prickly lettuce were also present in this field. Below is a compilation of pictures of these treatments and a summary of the results.
Horseweed control results
Roundup PowerMax (glyphosate) alone was ineffective at controlling a majority of the horseweed plants in this field (Figure 1A), indicating this population is highly resistant to glyphosate. Glyphosate-resistant horseweed is extremely common in many Michigan fields and glyphosate alone should not be used. The addition of 2,4-D ester at 1 pint per acre (pt/A) or 1 quart per acre (qt/A), Enlist One at 1 pt/A or Clarity (dicamba) at 1 pt/A to Roundup PowerMax improved horseweed control. However, controlling horseweed with these treatments only ranged from 60–70% 14 days after treatment (Figure 1B). These treatments will not likely result in complete control of horseweed.
The addition of 2,4-D or dicamba also improved common lambsquarters and common ragweed control over Roundup PowerMax alone. While these may be some of the more inexpensive treatments, they were not the most effective and caution should be taken if 2,4-D ester or any of the dicamba formulations are used. Off-target movement by drift or volatility, especially under high temperature conditions and when sensitive crops are in the area, can occur these herbicides.
The most effective treatments to control glyphosate-resistant horseweed were Liberty (glufosinate) at 32 fluid ounces per acre (fl oz/A) plus AMS (Figure 2A), or Sharpen at 1 fl oz/A or 2 fl oz/A plus Roundup PowerMax at 32 fl oz/A plus MSO plus AMS (Figure 2B). These treatments resulted in greater than 95% control of horseweed, common lambsquarters, common ragweed and prickly lettuce. A higher rate of Liberty (glufosinate) at 43 fl oz/A can also be used.
Initial control of glyphosate-resistant horseweed with Gramoxone 3L (new formulation) at 2.67 pt/A plus surfactant was 80%. However, by 14 days after treatment, horseweed started to regrow (Figure 3). Controlling common lambsquarters, common ragweed and prickly lettuce ranged from 70–75%.
Two additional treatments we examined included disking and mowing. Mowing reduced overall weed biomass, however it also removed the primary growing point and as horseweed started to regrow, additional shoots were produced. If mowing, multiple passes throughout the season will likely be required. A onetime mowing would likely be more beneficial later in the season prior to flowering and seed set. Tillage or disking did provide good horseweed control, however it will likely take multiple passes to keep the fields clean throughout the season.
All these treatments were applied under good growing conditions (plenty of moisture and heat) and resulted in good herbicide activity. As weeds continue to grow and begin to flower, the effectiveness of these treatments will likely be reduced. Additionally, depending on the weed species, there could possibly be new emergence later in the season.
Crop rotation restrictions also need to be considered when choosing one of these herbicide treatments for horseweed and other weed control. Sharpen, 2,4-D and dicamba all have residual activity and could cause injury to certain cover crops and winter wheat if rotation restrictions are not followed. Winter wheat should not be planted earlier than one month after applying dicamba or 2,4-D (Enlist One). Sharpen at 1 or 2 fl oz/A can be applied any time before planting winter wheat. There is a 70-day rotation restriction between Liberty applications and planting winter wheat. Consult individual herbicide labels.