By Don Osmond
Don is a long-time expert volunteer steward. He invites suggested edits and feedback generally.
Veteran practitioners will be tempted to skip this article, but I tried to include items of interest for all skill levels using a wide variety of high quality sources plus my own experience.
If I could suggest only one thing to herbicide applicators, what would it be?
Get the herbicide operator/applicator study guide for your state & read it cover to cover. It’s easy to forget stuff or develop bad habits & hitting that guide every few years for my license renewal was an excellent way to get back on track.
How to decide if herbicides are needed
An invasive species management plan is essential. It sets priorities for each invasive & land parcel based on available resources for the number of years required to suppress the invasive to the desired level. It forces you to think about the entire ecosystem, the life cycle/seed longevity of each invasive & whether herbicide use makes sense. At the steward level, you don’t need the rigor of an ecologist generated site restoration plan. It’s fun to watch the plan evolve as you learn new things & it serves as a blueprint for your successor, so all your hard won knowledge isn’t lost. There are many other benefits to a plan, such as nailing down the dates when mechanical control should start for each invasive & at what date to switch from one invasive to another.
Explaining to visitors (and reminding yourself) why herbicides are necessary
Most of us would probably not use herbicides if each nature preserve had an army of young, physically fit volunteers or contractors who were available over 4-12 consecutive years at the right time period to cut, pull or dig every weed. Since that will never be the case, most of us will need to herbicide. The exceptions are sites that are very small, have good native competition with few weeds or where the management goal is not related to preserving or increasing the percentage of conservative plant species. The following are some reasons to use herbicides:
- In the 1960’s, Rachel Carson correctly shifted public opinion away from the view that large scale use of pesticides have no risks. But concluding that all pesticide use is bad would be an overcorrection. A balanced approach is usually the best & that means using the proper techniques to apply low toxicity herbicides targeted at specific plants or patches.
- Mechanical control of weeds without herbiciding can overload the restorationist for several reasons. It must occur in a limited window of time. The plants usually must be in bloom to ensure finding most of them, but if you wait too long, seeds are set. Plus some weeds like wild parsnip & sweet clover have a proportion of plants with delayed emergence, requiring multiple passes separated in time, taking time away from controlling other invasives. Weeds can have occasional bumper crop years due to the plant’s life cycle, controlled burning, brush clearing, etc. Also, some years can be too hot or wet to finish mechanical control before seed drop. Seed drop must be avoided at all costs if native competition is weak or the soil microbial diversity is low, because it can set you back years, depending on seed longevity.
- I used to think about each invasive plant in isolation, but now I see that all the efforts during a given growing season are related to each other. For example, if I herbicide wild parsnip in the fall & spring, that reduces the time needed to mechanically control it in summer, which in turn allows me to get white sweet clover at peak bloom when it is easily found, which in turn lengthens the knapweed window, giving me time to dig or pull the root out instead of the less effective but quicker method of wacking. So herbiciding just one invasive increases your effectiveness for multiple invasives, making it more likely you can increase your weed control area over time.
- Herbicides are essential for woody plant control.
- Some other advantages of herbicides are the ability to get multiple generations simultaneously for biennials, less physical toll on the body compared to mechanical control, better control for invasives that reflower compared to cutting or mowing & less disturbance of soil for invasives that must be pulled or dug (soil disturbance=more weeds).
Keep-out areas
I don’t recommend herbiciding in high quality remnants, with the exception of careful application to crown vetch and woody plants. In addition to the possibility of off-target kill, we don’t know enough about herbicide effects on the soil microbiome. If you think herbiciding in a remnant is necessary, consult with an expert first.
In addition, I avoid shores, riverbanks, areas known to flood if heavy rain is forecast a few days after spraying & well traveled footpaths.
How do I know if herbicides are working?
Seeing the leaves curl & turn color may not be enough. You want to be sure the root was killed & not just the top. When trying a new herbicide/adjuvant or concentration, flag a spray plot & a nearby non-sprayed control plot with the same density of weeds, competition level & habitat type in each. It’s helpful to have 3 spray plots with concentrations a bit above & below your target to see if you are on the edge of effective control. Monitor a year later to verify density reduction compared to the control plot. Again, the climate should have been somewhat average during the previous year. Make sure no controlled burns occur in the year after application because that may affect results. Also, don’t experiment if the weather before spray time has been abnormally wet or dry. Relying on the experience of others can provide a starting point for herbicide use, but there are enough variables involved to warrant doing your own experiment before spending a lot of time & money.
Treatment failures
If a treatment fails, you may not know about it for months since root death won’t be evident until the next growing season. That could mean a lot of work down the drain, so it’s important to get it right the first time. Good detective work is needed to find the root cause of failures, so it’s best to investigate your entire process for the following:
- Errors in calculating concentrations, sprayer calibration or mixing.
- Rain too soon after application or applying with too much dew on the leaves.
- Not getting enough herbicide on the plant, especially true for painting, rolling or wick/sponge application.
- If multiple people have access to herbicide: somebody created a custom mix or transferred herbicide & forgot to relabel the jug.
- Spraying foliage when the plant isn’t actively growing or is under drought stress. Also, some plants are most vulnerable during the stage when they are pushing resources into the roots.
- Using hard water with glyphosate without a water conditioning additive like spray-grade ammonium sulfate. One study found a 60% decrease in toxicity when used with water at 50 ppm hardness.
- A mix that is above or below the label recommendation for concentration or rate. If you experiment with a lower rate, failures can occur even if your experiment was successful. The lower rate may work for a given competition level, stage of growth, age of plant, drought severity, etc but if those variables change, that rate may no longer work. Recommended rates create a margin that reduce the effect of variables. If you try a rate higher than recommended, it may kill the leaf too quickly, interrupting translocation to the root.
- Not using an adjuvant such as methylated seed oil.
- Spraying rosettes too early, resulting in many new plants emerging after spray application, making you think the application failed.
- Inconsistent spray method for a given applicator or inconsistency due to having multiple applicators. Also poorly trained applicators.
- For clonal plants: not treating every stem or treating only part of the clone & then waiting too long to finish the rest of it. Note that clones (especially older ones) can require several years of repeat treatment,
- For woody plants
- Waiting too long between cutting/frilling & herbicide application
- For basal bark: band of herbicide too narrow or not herbiciding the entire circumference
- Not cutting stems close to the ground
- Not cutting horizontally (herbicide runs off the cut stump)
- For some plants like dogwood, herbiciding when the plant is pushing sap upward in the spring.
Off-target kill
Spraying invasives when native plants are green will be a judgement call based on what is best for the entire ecosystem in the long term. Sacrificing a small number of common native plants is usually acceptable if the invasive plant being sprayed is known to displace natives, the invasion is beyond what mechanical control can handle & your management plan designates the area as high priority.
Practice proper technique regarding wind speed limits, nozzle height above ground & nozzle type (avoid those with droplet size rated as “fine”). Decide if the weed can be effectively controlled in the rosette stage when most natives are dormant.
Wind causes spray drift, but with the low pressure sprayers we typically use, it is often not a big deal. Plus the wind at ground level is much less than at your head. I’ve sprayed in degraded areas with no problems up to 15 mph average as long as gusts are below 20 mph. For spraying where many natives are present, spraying near property lines or for foliar brush spraying, winds should be below 7 mph or so.
Exceeding the maximum use rate on the label may result in off-target kill or unintended environmental effects. This rate is listed in a different place than the spray rates for particular weeds. For example, the Garlon 4 label states a max use rate of 8 quarts per acre per year for cut stump/basal bark. Lets say you want to basal bark a 30’ x 30’ brush clone. Convert to acres: (30 * 30) square feet/43560 square feet per acre = 0.021 acres. 8 quarts per acre * 0.021 acres = 0.168 quarts or 0.158 liters is the maximum amount of Garlon 4 you can use. If you mix Garlon 4 at 20% in bark oil, that means 0.158 liters/20% = 0.79 liters or 27 ounces of spray solution in your tank or bottle is the max you can use on that clone in a year. I use about 1.2 liters in 6 hours of cut stump treatment of small diameter brush.
If the label indicates potential for volatilization, don’t use when temperatures are in the 80’s or higher.
Don’t apply oil based solutions when ice is on the ground because the herbicide will readily move off-target.
See the woody plant section for more.
Dealing with precipitation
Some labels don’t specify rainfastness. Rain too soon after application can reduce efficacy & potentially cause off-target kill due to runoff. I shoot for 8 hours rain-free after application but that may be overkill. Basal bark requires a few days rain-free (see woody plant section).
“I have a pair of chemical gloves from a home improvement store & I’m careful not to walk in sprayed areas that are still wet. Good enough?”
I’m afraid it isn’t. We have to think about long term exposure to any type of chemical, whether it’s in our everyday life or while herbiciding. The reason to wear protective equipment is not because herbicides are highly toxic, but instead as an insurance policy to keep exposure to a minimum over many years of use. The degree of exposure for yourself is a personal decision, but if non-applicators are present while the herbicide is wet, assume they want zero exposure. I’d like to hear from others on how they ensure volunteers at group events never walk into wet herbicide. Do you have a systematic way for applicators to follow the brush cutters? Or do you delay herbiciding until the area is clear? If the latter, how do you find all the stumps if they are small & hidden in vegetation?
How to determine toxicity
The herbicide label contains a signal word from most to least toxic in this order: danger, warning, caution. Try to use the least toxic herbicide, but as a point of reference, household bleach & toilet bowl cleaner are labeled “Danger”. If the label recommends chemical resistant footwear or an apron for mixing/loading, consider substituting a less toxic herbicide.
If you hear about court cases regarding herbicide toxicity, research may reveal the plaintiff is not directly claiming the herbicide caused a disease or you may find the majority of credible scientific studies don’t support the plaintiff’s claims. Public & media understanding of science is poor, so juries are easily swayed by pseudoscience or their own antagonism against corporations. Any claim that an herbicide caused cancer in an individual cannot be proven beyond doubt because so many things can cause cancer, it’s impossible to know the relative contribution of a given substance.
What is the most risky activity?
Mixing & loading because you are working with undiluted herbicide. Always wear chemical resistant gloves & some form of eyeglasses, pour liquids from below eye level, block the wind from blowing the liquid stream around, have paper towels & water available to cleanup spills & have a bottle designed for eyewashing available, filled with fresh water.
Tips to minimize exposure
I’m not a fan of having open herbicide containers at the job site (e.g. using a paintbrush or roller) due to the potential for splashing or spilling on clothes or shoes with no means of immediately showering & changing clothes. The practice also increases the odds of getting it in your eyes.
Always wear some form of eyeglasses when using sprayers in case the trigger is accidentally depressed with the nozzle pointed at you.
Check state law, rules from your managing agency & the herbicide label to see if posting of signs is required in non-agricultural, non-landscaped areas. If herbiciding near active trails, you should post signs directing people & their pets to stay on the trail.
If you offload herbicide into a smaller container, always remove the original label of that container & relabel with herbicide name & concentration. Obtain containers that don’t look like they could hold food or drink.
Chemical resistant gloves
They are not a barrier, but instead slow down the process of chemicals migrating through the glove to your skin. National Institute for Occupational Safety & Health says chemical protective clothing should be the last line of defense, not the first. I don’t recommend regularly contaminating gloves with diluted or undiluted herbicide because by the time you rinse them, some herbicide has likely entered the glove material & will be making its way to your skin.
- Material: I couldn’t find breakthrough time data (time it takes for chemicals to travel through glove material) for herbicides we use. Schwope1 found that solvents (like those in Garlon 4 & bark oil) will break through the glove material sooner than most other chemicals & will take the other substances with them in the process. A generalization of their findings is that butyl rubber, nitrile rubber & PVA, all about 15 mils thick, were the best. Natural rubber & PVC were not recommended.
- Thickness: Never use thin disposable gloves. I’ve found 15 mil thick nitrile gloves are a good balance between cost, dexterity, availability & chemical protection.
- Maintenance: Illinois Dept of Agriculture & herbicide labels recommend washing gloves after every use, probably partly due to breakthrough time & partly to prevent contaminating your skin during donning & doffing. I replace gloves after 10 days of use or monthly (whichever comes first) to guard against eventual herbicide migration to the inside & potential degradation of the glove by physical movement & ultraviolet rays. If I accidentally get undiluted product on them, they are discarded.
Why should I read herbicide labels when most of it is aimed at farmers?
- The label is the law.
- It gives the maximum application rates to avoid off-target kill & pollution of the environment.
- It gives application rates to control particular weeds. If you don’t see your weed on the label, there may be one listed in the same plant family to give you a starting point for concentration. Please don’t exceed these rates. More herbicide concentration is not necessarily better. For example, higher concentrations can kill leaves too quickly, preventing translocation to the roots. What if the label doesn’t mention spot spray but instead recommends amounts in quarts/acre? Assume you are using a 3 gallon backpack sprayer calibrated to 40 gallons/acre (see the backpack sprayer section for how to calibrate) & the label calls for a maximum of 5 quarts/acre or 1.25 gallons/acre for your weed. So to spray 1 acre you will use 1.25 gallons of product in 40 gallons of spray. 1.25/40 = 3.1%.
- It states how toxic the herbicide is & what protective equipment you must wear.
- It has valuable information such as use around wetlands & how persistent it is in the soil.
- Labels can change so download the latest one at regular intervals.
Spray additives
- Adjuvants: These include oil concentrates like methylated seed oil (creates better penetration of leaf surface-I use this in all my applications), surfactants (causes water to spread on the leaf instead of beading), water conditioners (offsets the negative effects of hard water on herbicides like glyphosate) & stickers (increases the ability of chemicals to stay on the leaf, leading to better rainfastness).
- Dye: Always use it because it alerts you to missed plants, prevents walking into sprayed areas, alerts you to leaks in the sprayer & makes it apparent if herbicide accidentally gets on your skin.
Backpack sprayers
- A sprayer setup for those without a pickup truck is shown below. The herbicide tote contains dye & herbicide offloaded into small, easy to handle bottles along with nitrile gloves, measuring cup & paper towels. For transport, the sprayer is put into a large plastic tote with a pvc pipe bolted to the inside, which holds the sprayer wand. Bungees are used to hold it down. To keep things clean, a plastic baggie is wire tied over the nozzle during transport.
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Portable backpack spraying setup |
- Shoulder straps are hard on the body so I bought a harness that transfer some of the weight from shoulder to hips. Unlike hiking backpacks, they are poorly designed & often need to be modified to fit well, but are still well worth it.
- Be situationally aware & walk slowly because the sprayer throws your center of gravity off. If you trip, step in a hole or lose your balance, the added weight of the sprayer can turn a minor injury into a major one.
- Get in the habit of engaging the trigger lock when not spraying to avoid accidental discharge.
- Hold the spray wand upright as you walk to prevent drips.
- As you walk, the sloshing herbicide can leak from the filler cap. Yep, it has happened to me-right down my back. First, look at the cap gasket to make sure it isn’t twisted from the factory. Buy gasket grease from the manufacturer & use a Q tip to apply it every month. This will help the gasket remain soft & seal better. Obtain a white sock made from absorbent material & cut a few inches wide section from it. Each time you screw the cap onto the sprayer, stretch this sock section over the cap so it rests just below the bottom edge of the cap. This will absorb leaks & will alert you to the need for gasket maintenance by dye discoloration of the sock. Walking slowly & steadily when the sprayer is full will minimize herbicide splash into the cap area. Never lean forward since that can cause herbicide to leak from the cap vent hole on some sprayers.
- You can wear a fanny pack across your chest or gear vest to carry cellphone, gps, maps, first aid, cleanup kit for sprayer leaks, water, food, etc
- For some sprayers, every few weeks use nitrile gloves to unscrew the nozzle over a drip catcher. There may be a small screen in there that can be rinsed or wiped clean. During disassembly, note the order & orientation of the nozzle components so you can put it back properly.
- At the end of the day, I put a little water in the sprayer & spray that out, then hold the sprayer up high to get all the herbicide out of the hose & wand. I don’t know if this is necessary, but I never have clogged sprayers.
- Calibration
- Labels don’t always tell you how much product to use per gallon of water by volume. Instead they tell you how much product per acre to use. That’s because herbicide customers are mostly farmers & landscapers who spray large areas with herbicide mixed in a big tank. In contrast, we spot spray with handheld or backpack sprayers.
- This process must be repeated for every nozzle you intend to use. You’ll need a tape measure, a way to measure time in seconds & a clear container marked in ounces. Put a gallon of water into the sprayer. Find a spot where it is safe to spray herbicide & mark a small area such as 20’ x 20’. Measure how long it takes to spray that area with the same sprayer pressure & height above ground that you typically use. Spray enough to wet the vegetation but not to the point of dripping. Now, refill the sprayer if necessary, spray into the container for the same amount of time & measure how much liquid is in the container. First, convert your test plot into acres by dividing square feet by 43560. For this case: (20’ * 20’)/43560 square feet per acre = 0.00918 acres. Let’s say you collected 56 ounces in the container. 56/128=0.4375 gallons. So you sprayed at a rate of 0.4375 gallons/0.00918 acres = 48 gallons/acre which is ballpark for a backpack sprayer with a hollow cone nozzle. If we use Garlon 4 as an example, the recommended application rate for broadleaf weeds is 1-4 quarts product per acre. If we choose 2 quarts/acre, that means we will need 2 quarts product in every 48 gallons of spray or 0.0417 quarts/gallon. 1 quart is 32 oz so that is 0.0417 * 32 = 1.3 oz product per gallon of water or 3.9 oz of product in a 3 gallon backpack sprayer.
Some herbaceous weeds
- Crown vetch (CV): See the 7/5/23 post on this blog. Herbicides used most often are Transline & Milestone, but be aware both are persistent in the soil & will harm some natives. The Milestone label has a good list of the plant families affected by it. The manufacturer (Corteva) recommends Milestone over Transline & the latter’s label doesn’t include CV as a controlled species. Multiple sources, including Corteva, report reduced herbicide effectiveness at bloom stage. It’s important to coat as much of the stem & leaves as possible. GPS is essential for not missing patches. Tom Wise (Military Ridge Prairie Heritage Area in southern Wisconsin) reports that the number of years to control a patch is highly variable & can take 5 years or more. He sprays known patches before blooming & for ones found at bloom stage, he rotary mows them into tiny pieces to prevent re-rooting & seed set, then sprays after it resprouts. That method may facilitate better herbicide coverage of all stems/leaves & may also reset the plant into active growth stage, when herbicides are more effective. Then again, it’s conceivable that mowing could create stem fragments that can re-root. Losure2 found no viable seed in mature CV patches & cited other sources that support mostly vegetative reproduction. They also found that stems without nodes won’t root themselves but stems with nodes will. So it’s unclear whether CV persistence after spraying is due to poor translocation to the entire root system, persistent seedbank, leaf/stem defenses that prevent herbicide entry or unsprayed nodes rooting themselves. More long term experiments are needed.
- Garlic Mustard: See the 5/10/23 post on this blog for my method in mostly degraded woodland without the resources to perform consistent mechanical control on a large site. In summary, after many years of experimenting, I settled on spraying small patches of 2nd year plants at full bloom & fall spraying moderate patches of 1st year rosettes, combined with cutting or pulling scattered or unsprayed plants. Large patches are left alone to see if a biocontrol develops. In higher quality areas, I only sprayed rosettes when natives were dormant. Many broadleaf herbicides & glyphosate are effective.
- Spotted knapweed: I believe herbiciding followed by wacking/cutting of missed plants is better than wacking/cutting alone for large populations in average quality or degraded areas. This is because seeds can remain viable for 7+ years & the plant can live up to 10 years. That means many years of wacking/cutting without missing a year, while also dealing with other weeds like sweet clover, something many sites will find hard to pull off consistently. Also, stems tend to lie down in the vegetation, making them easy to miss while wacking. Digging the root is an alternative to herbicides, but its labor intensive & often a large clump of soil comes out with the lateral roots, creating disturbance that leads to more weeds. It’s best to spray after a burn for better visibility of rosettes since they are hard to find in vegetation or thatch. Herbicides used most often are Transline & Milestone but be aware that both are persistent in the soil. The Milestone label has a good list of the plant families affected by it.
- Wild Parnsip. Combine spring (early to mid May) & fall (late Sept-Oct) herbiciding of rosettes with summer digging of the root. Spraying too early can result in missing late emerging plants. Soil temperatures will influence emergence dates in the spring. Spraying after a burn will ensure finding more rosettes. Mature invasions in areas with weak native competition or poor soil microbial diversity can take >4 years of effort. Flowering usually occurs in the 2nd to 4th year of life, so herbiciding rosettes is effective in targeting multiple generations. Delayed emergence creates a long blooming season requiring 2 passes of digging separated in time, which is another reason herbicides are helpful. Many herbicides will work. After 2 years of use, I’m happy with 0.5% Garlon 4 in water with 0.5% methylated seed oil. 0.5% Garlon 4 worked as well as 1% in an experiment I conducted.
Woody plants
- See other discussions on this blog.
- Commonly used herbicides are 20% active ingredient glyphosate in water or 20% Garlon 4 in bark oil, applied in winter or when native herbaceous plants are dormant. The following are the pros & cons of each herbicide. “Triclopyr” refers to triclopyr ester in bark oil & “glyphosate” refers to glyphosate + surfactant in water (cut stump only).
- Applying at below freezing temperatures: Favor triclopyr. But I had good results in the upper 20’s F & a local contractor uses it down to 10F.
- Applying among native bunchgrasses that are still green: If you have experimented & determined your methods don’t cause off-target kill, favor triclopyr.
- Basal bark: Triclopyr only
- If concerned about off-target kill (especially in remnants): Experiment before committing to triclopyr, including an untreated control plot. For cut stump, favor treating the cut surface only (instead of cut surface + stump sides) if your experiment shows it works. See “cut stump & basal bark off-target kill” below.
- If the smell of bark oil bothers you while transporting sprayers in a car or if you store them in the garage, favor glyphosate.
- If you have hard water & cannot find a source for spray grade ammonium sulfate, favor triclopyr.
- If you can’t treat the stump soon after cutting: Favor triclopyr.
- Also consider the differences in cost of each herbicide & the availability of bark oil.
- Clonal plants: These include dogwood & sumac. Treat a given clone all at once rather than piecemeal. A few years of treatment will often be necessary to kill the root system, especially on older clones.
- Methods include
- Cut stump or cut surface. The stem is cut as close to the ground & as horizontally as possible, then the stump is herbicided as soon as possible. If performed in that way, it is the most reliable method for controlling woodies, but is also the most labor intensive. Cutting low ensures best translocation of herbicide to the root, minimizes trip hazards, facilitates subsequent weed control & is better aesthetically. There are reports of cut stump herbicide failures with certain plant species, but there are also plenty of reports that glyphosate & Garlon 4/bark oil work just fine for all woodies (which is also my experience).
- It avoids having standing dead brush, which can be an impediment to controlling weeds after removal of dense brush clones, a deterrent to grassland bird nesting or an eyesore in some situations.
- Stems cut at a strong angle will have too much herbicide runoff.
- If snow forces you to cut higher than normal, be prepared for poor control. Don’t let snow deposit on the cut stump or herbicide will get diluted or run off.
- If you can’t spray soon after cutting (for example, waiting for volunteers to leave the area), favor Garlon 4 over glyphosate. Glyphosate based labels say to spray immediately after cutting, but I found Roundup effective in shady habitats on good sized buckthorn even with a 2 hour delay between cutting & herbiciding3. One theory is that the stump dries out over time, reducing it’s ability to absorb water based herbicides. So delays may be more of a problem in sunny areas or if humidity is low. In an experiment, I found a small percentage of buckthorns resprouted after Garlon 4/basal oil herbicide treatment in a shady habitat (even when applied immediately after cutting), but after 2 years the resprouts died. So a long followup period is needed before declaring success or failure. The Garlon 4 label recommends spraying the sides of the stump as well as the cut surface to control resprouts. That may increase off-target kill if enough herbicide falls on the soil nearby. I have good results treating only the cut surface, but it’s likely there are situations when treating the stump sides are necessary.
- Note that painting the stump with a roller, brush or sponge may not apply enough herbicide to be effective, so experiment before settling on that method. It’s interesting to note the Garlon 4 label mentions spraying for cut stump or basal bark but not rolling or painting, perhaps an indicator that those methods are not consistently effective.
- Basal bark. The stem of the uncut plant is coated in herbicide (typically 20% Garlon 4 in bark oil) from the ground to a particular height based on stem diameter & plant species. The oil helps the herbicide penetrate through the bark.
- If significant rain falls within a few days after application, runoff can cause off-target kill.
- You may have a dead zone around the treated plant if the herbicide is applied in spray form.
- As with cut stump, painting or rolling onto the bark may not transfer enough herbicide compared to spraying.
- It’s best to conduct an experiment to verify that your choices for the application dates, amount of bark treated, application method & herbicide type/concentration is effective on all species of interest before you treat large areas.
- Cut stump & basal bark off-target kill. There are reports of this (see 8/28/20 entry on this blog) but many others report no such problems. Potential causes include root exudation of herbicide into soil4, movement of herbicide by mycorrhizal fungi, rain runoff, overspray error or exceeding the labeled maximum use rates. Woody plant herbicide mixtures are much more concentrated than herbaceous mixtures so it doesn’t take much in the soil to cause problems. That is why I use a solid stream nozzle instead of a cone or flat fan for cut stump, so I can flow herbicide onto the stump.
- Foliar spray. The leaves are sprayed on shrubs, small seedlings or resprouting mowed/cut brush in degraded areas or if the woody plant is leafed out while the native ground layer is dormant. This can be a very risky method. Usually large areas need to be sprayed with the nozzle far above the ground, which increases the possibility of wind drift onto the applicator & the ground layer nearby. There are plenty of reported failures with foliar that may be related to herbicide concentration/type, species of woody plant or season of application, so conduct a 1 year experiment before treating large areas.
- Frill. Cuts are made in the bark & cambium around the stem using a hatchet or similar tool, then sprayed with herbicide. See other posts on this blog.
- Spray equipment
- Handheld sprayers
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Handheld sprayers L-R: lower quality Hudson 62227, high quality Tolco 942 |
- Drawbacks are the need to stoop very close to ground level & the weight combined with pulling the trigger all day is hard on your hand & wrist. Stooping risks eye or nose injury in dense brush clones.
- Avoid the cheap ones at brick & mortar stores. If they don’t leak from the get go (often from the pump shaft if you tilt the bottle too far off vertical), they will leak or fail sooner rather than later.
- See grasslandrestorationnetwork.org/2020/11/05/hand-held-herbicide-sprayer-comparison/
- 2 quart capacity is necessary for a full day of cut stump without refilling.
- To keep the bottle outside surface free of poison ivy & herbicide when working alone, place it in a 5 gallon bucket when not spraying. Use spacers of some kind to place the sprayer in the bucket such that the nozzle sits over a drip catching tray.
- Standalone sprayer
- Advantages are no stooping required, the trigger is easy on your hands/wrist & a wide selection of nozzles are available.
- I put the sprayer in a bucket as shown below. Without the bucket, the sprayer will tip over on uneven ground & can become contaminated with poison ivy & herbicide. It also makes working alone much easier. I can spray some stumps soon after cutting so all can be found, hang the sprayer wand on the coat hook, cut some more stumps with loppers, then spray again. The nozzle I use is a single stream type, which is just a cylindrical tube. With low pressure, a light hand & a hose clamp trigger stop, I can place the nozzle against the stump & flow just enough herbicide to prevent drippage onto the soil.
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Woody plant spray fixture for working alone. Sprayer is Smith 190504. |
References
1) Schwope, A. D., etal, 1992, Permeation Resistance of Glove Materials to Agricultural Pesticides. AIHA Journal 53(6):352
2) Losure, D.A., K.A. Moloney and B.J. Wilsey. 2009. Modes of crown vetch invasion and persistence. American Midland Naturalist 161:232–242.
3) Osmund, D., 1997, Cut-stump treatment of buckthorn effective despite two-hour delay between cutting & spraying (Illinois). Restoration & Management Notes, 15(2): 197.
4) Graziano, G, etal, 2022, Herbicides in unexpected places: non-target impacts from tree root exudation of aminopyralid and triclopyr following basal bark treatments of invasive chokecherry (Prunus padus) in Alaska. Weed Science, 70(6): 701-714.
This is what should be covered in herbicide training. A field manual should be written for people to take with them when applying herbicide. I commented on individual items below.
ReplyDeleteSoil Disturbance
ReplyDeleteMany small weeds (sweet clover, small purple loosestrife) can be removed in a manner that causes a minimal amount of soil disturbance. If I cannot pull these weeds then I use a narrow-bladed weeding tool, like the NRG Pro Weeder, to remove them. For other weeds (Queen’s Annes Lace, Wild Parsnip, etc.) a sharpened narrow-bladed shovel, like the Root Slayer Perennial or previously available Parsnip Predator, will cut the weed’s root several inches below the surface of the ground killing these weeds.
For the NRG Pro Weeder, I insert the tip of the tool into the ground under the root or into the ground down as far as possible adjacent to the weed’s root. I use a half log as a fulcrum to distribute weigh and prevent soil compaction. When I press down on the handle of the tool, the weed is lifted upward from underneath. This pulls the soil away from the weed’s root in all directions. I only apply enough downward pressure on the tool to pull the weed free from the soil. I then shake the soil aggregates attached to the roots back into the opening left from pulling out the root. When I remove pressure from the handle of the weeding tool the opening in the ground closes. I then press the edges of the opening back together and downward, so the edges of the soil surface are touching and the surface is again level with the surroundings. I avoid mixing soil layers as occurs when people dig a hole.
This operation cuts some roots which will impact plants. This can be minimized by removing weeds when soil is moist. My observation has been plants fill the void left after a weed has been removed in the above-described manner faster than when herbicide has been applied to kill a weed (even if glyphosate is used). We should consider that herbicides can cause soil disturbance too. It should also be considered that some sites have lots of volunteers but few herbicide applicators. Preventing volunteers from manually removing weeds can prevent more invasive species control from being accomplished in certain situations.
Herbicide Exposure
ReplyDeleteMy experience is it is much more difficult to avoid herbicide vapors than physical contact. I have not experienced contact symptoms wearing chemical resistant 15 mm (or greater) gloves when applying glyphosate or triclopyr ester in basal oil. At least this is true until the gloves get a puncture. Working away from areas that have already been treated allows an applicator to mostly avoid getting herbicide on their clothing. The vapors are much more difficult to avoid. This is a benefit of backpack sprayers with a long wand. If you get your face close to where herbicide is being applied, like when using a handle held sprayer, then it is wise to hold your breath. Stand up, catch your breath, then when you bend down to apply more herbicide hold your breath again and repeat.
In the above, I should have written "15 mil" instead of "15 mm."
DeleteHow do you find all the small stumps if hidden in the vegetation?
ReplyDeleteI put a utility flag by it then remove the flag once I treated the stem with herbicide.
I should have written, "I put utility flags by them and remove each flag as I treat the stems with herbicide."
DeleteThe attached link has a blog post I wrote showing images of flags by frilled sumac stems and one stem after being treated with herbicide.
Deletehttps://stewardshipchronicles.blog/2023/08/26/treating-every-stem/
Crown Vetch Persistence After Spraying
ReplyDeleteI have seen crown vetch reappear many times after herbicide treatment. In one location this observation spans over a decade. I can assure you that even if it looks dead, when it grows back the following year the crown vetch is growing from the roots. The regrowth is too vigorous to be seedlings.
Painting Stumps or Basal Bark With a Roller, Brush, or Sponge
ReplyDeleteMy observations from numerous sites, see my Stewardship Chronicles Blog, is that painting stumps can be effective if enough triclopyr ester is applied. The best application I have recorded to date was done at Bluff Spring Fen.
https://stewardshipchronicles.blog/2023/06/19/bluff-spring-fen-preliminary-results/
In contrast, I have seen applications fail when people sprayed stumps. I believe this occurred because the cut and one side of the stump was sprayed too lightly. My observation has been that it is not whether a painting method or spraying method is used that determines effectiveness, but rather how much herbicide is applied. Painting triclopyr ester in basal oil onto the cut of stumps heavily enough that it coated the bark a few inches down has given good control. Painting triclopyr ester in basal oil onto stumps with no-drip methods when rain is not forecast for at least four days has eliminated the “ring of death” for me.
Like cut stump, basal bark application can be effective if enough herbicide is applied. For larger trunks, this can be significantly more herbicide than is needed for cut stump treatment. My best control rate and least off target damage has been when I apply 25 to 41 percent glyphosate (depending on species being treated) to cuts around the trunk (frilling). This method should be considered over basal bark treatment once trunks reach a certain diameter determined by prior experience and objectives at a given site.
Here are two Facebook posts I made last year showing the results of applying triclopyr ester in basal oil with a mini-paint roller to Asian bush honeysuckle during the dormant season. I completely coated the circumference of each stem covering a length of about six inches, which was more than enough for these sprouting stems killed back to the ground by previous fire.
Deletehttps://www.facebook.com/groups/356617574475489/permalink/2501710746632817/
https://www.facebook.com/groups/356617574475489/permalink/2507822659354959/
The Forest Preserve District of Cook County (FPDCC) has an excellent herbicide training manual, Practical Herbicide, and it is available online at
ReplyDeletehttps://fpdcc.com/wp-content/uploads/2022/01/FPCC-Volunteer-Herbicide-Manual-010322.pdf
In particular it lists the various types of herbicides that are commonly used in restoration efforts and the mixing percentages by volume of the concentrates that are used against typical weedy species. What is often not made clear by others when recommending percentages is that they are percentages by volume of a concentrate, not percentages either by volume or by weight of active ingredient.
The percentage shown on a concentrate container label or on the label of a herbicide premix as sold in a garden store is a percentage by weight of active ingredient. If a percentage by weight of active ingredient of a mixture is needed for a more accurate scientific report, then it can be calculated using some algebra and some density information for each of the components used in the mix. Density information can usually be found in the Material Safety Data Sheet (MSDS) of each component used in the mix.
Thanks for the link & I agree it is a valuable document. One exception is their approval of using a gloved hand to apply herbicide. The only way I could call this a safe practice is if they recommend a particular thickness & material type for the glove & also can point to a high quality study that shows the herbicide plus adjuvant they recommend has a long enough breakthrough time to allow a day’s use before discarding the glove. I can’t find any such studies for herbicide formulations we use.
DeleteThanks also for pointing out that when I say x% of Garlon 4 or “product”, I’m referring to volume & also to the product as commonly sold, not the active ingredient.
Thanks for that good reference. The old Monsanto formulation of Roundup contained a proprietary adjuvant as well as glyphosate & I assume current formulations have their own adjuvant. So it is possible the adjuvant could breakthrough first & carry glyphosate with it through the glove. Having said that, the right answer is for each person to decide their own level of risk once they have all the relevant information, as you have done.
DeleteI wish independent scientific research was available on the topic. I do not like that I have to trust a chart provided by the manufacturer with no supporting details. Often, not enough information is provided for me to feel comfortable with a decision.
DeleteHere is another chart that includes Roundup, instead of glyphosate. As you predicted, the breakthrough time is rated less for the herbicide than the pure active ingredient.
Deletehttps://www.globalglove.com/media/wysiwyg/features/pdfs/Global_Glove_Chemical_Resistance_Chart_and_PVA.pdf
That's a good find. I agree that a peer reviewed study is better than a manufacturer's claim, but the latter is probably the best we can hope for. I see their data came from a book that is currently in the 7th edition. It would be interesting to check if it's available by interlibrary loan to find out if any other herbicides are listed.
DeleteI leave all the woody species I control standing. I do not have the resource to cut, haul, and pile it all. I want to avoid burn scars.
ReplyDeleteMost of the woody species fall within a few years. It can make a temporary mess. By the time the roots have rotted, and the woody species have fallen over, the wood is very brittle. I step on the smaller branches, and they shatter. I always able to get into areas to control invasive species. I just lift my foot up high, step on the branches, and they break into pieces. If the brush is still standing, I just use pruners to clip branches out of the way. In contrast, thickets of multiflora rose are a deal breaker for invasive species control.
Some hardwoods will stay standing as snags. These might take up to 25 years to fully decompose if they do not catch fire. I enjoy watching these snags slowly decompose. The woodpeckers use them.
In the end, cutting, hauling, and removing/burning wood mostly makes a minor difference in the outcome compared to leaving wood to decompose. In both methods, tall goldenrod near monocultures often develop if the invasive species have shaded all the native vegetation to death.
If logs are large enough, plants that will grow in low nitrogen conditions can colonize. However, most of the logs from species being controlled are not large enough to allow plants to grow. The tall goldenrod and other weedy natives do seem to be suppressed where brush has fallen. However, what colonizes these areas can be nitrogen-fixing crown vetch if it is present.
I am trying to control crown vetch and seed into areas where decomposing wood has suppressed the growth of weedy natives. It will still be a few years before I see if my efforts have been successful.
Is parsnip not biennial? “Flowering usually occurs in the 2nd to 4th year of life”
ReplyDeleteI also thought it was biennial but the reference below classifies it as a monocarpic perennial, meaning it‘s a perennial until it sets seed & dies. They refer to a study that states the plant typically flowers in years 2-4. The rosette must reach a certain size before there are enough resources to produce a flowering stem.
DeleteSource
https://cdnsciencepub.com/doi/pdf/10.4141/CJPS09110
I’ve heard something similar about burdock.
DeleteWhat is the principle behind cutting stems low?
ReplyDeleteThe higher you cut, the less chance that herbicide will translocate to the root if you treat only the cut surface, as I do. When using an oil carrier, the Garlon 4 label recommends treating the sides of the stump as well as the cut surface to control resprouting. Using that method would probably allow you to cut high. I like to keep herbicide out of the soil as much as possible, so I treat only the cut surface. I just checked some dogwood clones I treated last spring & found no resprouts, even those I sprayed in April when sap was flowing out of the stumps. But I suspect there are cases where treating only the cut surface failed. The other reason to cut low is to minimize trip hazards & reduce impediments to subsequent weed control & seeding.
ReplyDeleteI’m glad you brought this up & I’ll edit my original article to give more detail on cut-stump.
I also think the kill rate would be much higher if chemical covered the bark to the ground, like the manufacturers say to do. I don’t do it because a lot more chemical would be used and a lot would end up directly on the ground. I have a feeling the increased kill rate would not be due to better translocation but killing the buds at the root collar.
ReplyDeleteI wonder how much the height of the cut stem matters given chainsaw frilling/girdling and treating is effective done a couple feet or more off the ground. I tend to cut stems pretty low to make them less of a tripping hazard anyways.
Last thing, if glyphosate degrades as immediately upon contact with soil, might it not be a better chemical to use? I know of one expert who uses it even in winter, he keeps it from freezing in a cooler. I use it on hot days for its low volatility but triclopyr and bark oil otherwise. It supposedly isn’t effective on honeysuckle and a couple other plants though.
I’ve seen resprouting after treatment of Garlon 4/bark oil on buckthorn when snowpack forced ~1 foot high cut & only the cut surface was treated.
DeleteI used 50% Roundup (which is 20% glyphosate) in soft water all through the winter for many years on buckthorn with no resprouts. There are mixed reports on glyphosate effectiveness on honeysuckle but plenty of restorationists say it works fine. One study compared 15% triclopyr in oil with 20% glyphosate in water applied in early January, mid April, late April & mid May. Both treatments were equally effective. I used 50% Roundup from September through March at one site & didn’t notice any honeysuckle resprouts when checked the following August.
Glyphosate failure reports may partly be related to using hard water as a carrier or not applying herbicide immediately after the cut.
You’re right, the ability to quickly bind to soil while it degrades is a major advantage to glyphosate, plus it doesn’t have the smell of bark oil. I prefer it for cut-stump except while working in remnants when native bunchgrasses have a bit of green showing. Then I use Garlon 4.
Question One: What is the principle of cutting stems low?
ReplyDeleteSimply put, less herbicide tends to be needed to kill the plant. It is insightful to cut stumps very high and apply about the same amount of different concentrations of glyphosate to the cut and see how far down the stem the woody invasive plants are killed. This is useful to know since you cannot always apply the herbicide low to the ground. When I apply glyphosate to frills on buckthorn, I often must make the cuts higher up the stem. It is impossible to get lower on the back of stems in the middle of multi-stem buckthorn. When frilling, the cuts I make low to the ground get 25 percent a.i. glyphosate and the cuts I must make high above the ground get the full 41 percent a.i. glyphosate concentrate.
See my write-up (with pictures) in the below link.
https://grasslandrestorationnetwork.org/2018/02/18/cut-stem-treatment-on-buckthorn/
In contrast, triclopyr ester in basal oil does not kill the stem down a given length depending on how much herbicide was applied. Either enough herbicide gets into the vascular system to kill a plant or too little and the plant survives. Applying triclopyr ester in basal oil higher on larger buckthorn can make the herbicide more effective because bark is thinning higher up the trunk and more herbicide gets transported into the plant.
I should have written, "... because bark is thinner higher up the trunk ..."
DeleteQuestion Two: Will the kill rate be higher if triclopyr ester in basal oil covers the bark all the way to the ground?
ReplyDeleteCovering the bark with triclopyr ester in basal oil all the way to the ground will not necessarily improve control. I apply triclopyr ester to basal oil to the basal bark in areas so dominated by buckthorn there is little to no herbaceous vegetation in the understory. I must apply more herbicide (while achieving a lower rate of control) than people who cut buckthorn and liberally apply triclopyr ester in basal oil to the cut on the stump. The triclopyr ester in basal oil applied to the cut stump is put directly into the vascular system of the plant. In contrast, the triclopyr ester painted on the bark must migrate through the bark to get into the vascular system of the plant. Much more herbicide put into cuts (be it stumps or frills) gets into plants. For the same size plants, an applicator will get much better control if herbicide is put on a stump or into a cut, when frilling, versus painted on the bark when the same amount of herbicide is applied.
Question Three: Will applying triclopyr ester in basal oil to the bark get a lot more chemical on the ground?
ReplyDeleteIt depends on how you apply the triclopyr ester in basal oil. I use mini-paint rollers to apply this herbicide to the bark. Once a mini-paint roller has stopped dripping into the bucket, I use it for an application. I roll the mini-paint roller across the bark slow enough that centrifugal force does not spray herbicide off the roller. I stop applying herbicide about an inch above ground level. I call this no-drip technique. I do not get herbicide runoff onto the ground using this technique.
If rain does not occur for at least four days (longer is better) damage to herbaceous vegetation near the treated stem can be avoided. In areas heavily infested with buckthorn, I have observed that the establishment of early colonizing species is suppressed, and non-target woody species show impacts, when I use triclopyr ester in basal oil. My observation is this is true when triclopyr ester in basal oil is used regardless of if it is applied to only basal bark or cut stumps with it running down a few inches of basal bark. See next question for more information.
Question Four: Does applying triclopyr ester in basal oil to the basal bark result in better control because it kills the buds at the root collar?
ReplyDeleteMy experience has been the amount of triclopyr ester that gets into the plant’s vascular system is what is important. I have seen buckthorn stumps cut low before herbicide was applied to the cambium and an inch or two of bark. The herbicide applied was not enough and the buckthorns sprouted the following year. In contrast, I have applied a much larger amount of triclopyr ester in basal oil a few feet up the trunk of larger common buckthorn (where the bark is thinner) and have gotten better control then when I applied triclopyr ester in basal oil to the basal bark (where the bark is thick). See question one for more discussion.
Question Five: Would glyphosate be a better chemical to use to avoid off-target impacts?
ReplyDeleteThe quick answer is yes. If rain does not occur for at least four days after an application of triclopyr ester in basal oil to basal bark then damage to herbaceous vegetation near the treated stems can be avoided. In areas heavily infested with buckthorn, when I use triclopyr ester in basal oil I have observed that the establishment of early colonizing species is suppressed, and non-target woody species show impacts. My observation is this is true when triclopyr ester in basal oil is used regardless of if it is applied to basal bark (more herbicide) or cut stumps with it running down a few inches of basal bark (less herbicide). The link below has images of the results of a workday where triclopyr ester in basal oil was applied to cut stumps. Where enough triclopyr ester in basal oil was applied to kill the woody invasive species, you can see the herbaceous vegetation is sparse compared to areas where too little herbicide was applied to kill the invasive woody species.
https://stewardshipchronicles.blog/2023/07/25/middlefork-savanna-7-22-2023/
When I apply glyphosate to frills around common buckthorn in dense stands, the area fills with pilewort the next year, then tall goldenrod and tall boneset. These are not conservative, but they establish faster than if triclopyr ester was used. If I apply 25 percent a.i. glyphosate to frills I do not see off target damage to nearby woody species. If I apply 25 percent a.i. glyphosate twice to frills or apply 41 percent a.i. glyphosate to frills, then nearby woody species are impacted. What is impacted is usually just nearby untreated common buckthorn, but in one case a prairie crabapple with root connections was killed. The death of this prairie crabapple is the reason I trialed lower concentrations and now use 25 percent a.i. glyphosate when applying to frills made low on stems near the ground.
I should clarify, the sentence "If I apply 25 percent a.i. glyphosate twice to frills or apply 41 percent a.i. glyphosate to frills, then nearby woody species are impacted." was in regard to treating common buckthorn. I apply 41 percent a.i. glyphosate to frills around box elder and white mulberry without observing impacts to nearby woody species. For hard to control box elder and white mulberry, the frill often heals and I must make cuts a second time and apply more 41 percent a.i. glyphosate to achieve control.
DeleteHere is a blog post I wrote showing off-target damage to adjacent common buckthorn after 25 percent a.i. glyphosate was applied twice to frills around common buckthorn stems.
https://stewardshipchronicles.blog/2023/05/15/off-target-damage-from-applying-glyphosate-to-frills-cuts-around-stems/
Question Six: Can glyphosate be used in winter?
ReplyDeleteI had an application fail when I applied glyphosate to frills around sumac stems in February. This same treatment technique was 100 percent effective when done in November. The season when herbicide is applied is often important and needs to be considered. For some other species winter application of glyphosate is effective. Success of an application may even depend on the weather during a particular winter.
See comments in “Strategies for Stewards: from woods to prairies” post “Nature, History, Celebrities, Scandal” for more discussion.
Question Seven: Is glyphosate effective on Asian bush honeysuckle?
ReplyDeleteYes, if enough is applied to frills (around every stem) or cut stumps glyphosate will kill Asian bush honeysuckle.
The Wisconsin DNR used triclopyr and oil, never glyphosate, it makes me wonder if they know something I don’t.
ReplyDeleteBesides degrading quickly another advantage of glyphosate is mixing it with water instead of bark oil which isn’t available locally in SW Wisconsin.
Since many credible sources are perfectly happy with either herbicide, the best choice is what works for your particular site. I GPS my work & record the date & herbicide concentration so I can check it next season for resprouts & off-target impact. An agency could settle on a particular herbicide for multiple reasons including institutional momentum, cost or their past experience.
DeleteFor bark oil, some farmer's coop's don't require a business account to make a purchase. www.siteone.com may be an option but I don't know if you need to be a business to setup an account.
I think the point Don Osmund mentioned that is most important in triclopyr ester in basal oil being selected is cost. Spraying triclopyr ester in basal oil onto bark is much faster (and therefore cheaper) than other methods. The tradeoffs are damage from over spray or rain washing/splashing herbicide onto the ground/adjacent vegetation if rain occurs too soon after the application. I would not spray triclopyr ester onto basal bark in high-quality areas, but some people have so much area to manage, with too little resources, they have decided on speed rather than a method that causes less off-target damage.
DeleteIn summary, triclopyr in oil has no advantages over glyphosate for treating stumps, stems and frills?
ReplyDeleteThe only things triclopyr in oil can do is not freeze and be used for basal barking?
I changed my above comment to better reflect what I was trying to say.
DeleteA big advantage of triclopyr ester in basal oil is it can be applied in below freezing conditions. In ideal conditions, no chance of rain for at least four days (more is better) during the dormant season, I apply triclopyr ester in basal oil in high-quality areas using no drip technique.
Another advantage of using triclopyr ester in basal oil is that it is more effective on certain species than glyphosate. An example is box elder. Frills on box elder that have had glyphosate concentrate applied (41 percent) typically heal over at least once requiring more cuts and an additional application of herbicide.
Good opportunity to list the pros & cons for woody plant control with tricopyr ester/bark oil (which I’ll call “triclopyr”) versus glyphosate/water (cut stump only). I’m limiting the list to items that have a sufficient quantity & quality of evidence to support the findings.
Delete1) Applying at below freezing temperature: favor triclopyr. But I had no trouble with glyphosate in the upper 20’s F & a local contractor uses it down to 10F.
2) Applying among native grasses that are still green: favor triclopyr.
3) Basal bark: triclopyr only
4) If concerned about herbicide migration through soil to nearby native plants: experiment before committing to triclopyr or use glyphosate, keeping in mind we don’t know why some practitioners see this problem & others don’t. The triclopyr experiment can include treating only the cut surface (no soil contamination) versus treating the surface & bark down to the root collar.
5) If the smell of bark oil bothers you while transporting sprayers in a car or if you store sprayers in a garage: favor glyphosate.
6) If you have hard water & cannot find a source for ammonium sulfate: experiment before committing to glyphosate or favor triclopyr.
7) If you can’t treat the stump soon after cutting: favor triclopyr.
8) Also consider differences in the cost of each herbicide & availability of bark oil.
Below are my comments to a few of the points you list.
Delete1. I have successfully applied glyphosate down to 27- or 28-degrees F. Below this temperature the bark freezes. I apply glyphosate to cuts around stems (frilling). When the bark is frozen, it is difficult to cut. Instead of trying to cut into frozen bark, I apply triclopyr ester in basal oil when the bark has frozen if rain is not forecasted for the next few days.
2. I have seen rings of all vegetation killed, including grasses, around treated stems when triclopyr ester in basal oil has been sprayed on basal bark or has been applied using no-drip technique when rain occurred two soon after the application.
4. I kept records of the number of days until rain occurred for all my applications over the course of a year. I took a few representative images of the off-target damage that occurred the next growing season. I send these images labelled with the number of days until rain occurred after the application to Stephen Packard and many other people. I continue keeping records of number of days until rain has occurred after each application and continue to find this is the one variable that determines the extent of the ring-of-death. Science is a multiple people testing a hypothesis and reporting their findings. I welcome other people to keep records of number of days until rain occurs after applying triclopyr ester in basal oil and reporting what they find. My findings are not surprising. The smell of herbicide coming off the stems dissipates over several days as it volatilizes.
Is anyone on this forum a contractor that uses glyphosate rather than triclopyr?
ReplyDeleteIs there something close to a consensus that glyphosate is less ecologically harmful than triclopyr?
ReplyDeleteEvery herbicide I’ve used can be ecologically benign or harmful, depending on variables discussed in the article & comments. So I don’t believe there is an answer if your question is general in nature. But an answer is possible for a specific application. What herbiciding activity are you interested in, what is the season of application & what is the habitat type?
DeleteIt is a difficult question. Generally, for me weeds (field thistle, bittersweet nightshade, crown vetch) start to colonize the second growing season after an application of triclopyr ester in basal oil to the basal bark of common buckthorn in dense stands. I am working on controlling the crown vetch but not the other weeds. Others at Nachusa Grasslands who treat Asian bush honeysuckle have observed a better recovery than I do treating common buckthorn (see Kaleb Baker's study).
DeleteWhen I apply 26 percent a.i. glyphosate to frills, I have observed a better vegetation response than when I apply triclopyr ester in basal oil to bark. However, not much better. The season following an application of glyphosate to frills I get a lot of burnweed, and later spotted touch-me-nots (shaded areas) and sometimes a few guara before the tall goldenrod, and in drier areas also tall boneset, establish.
I trialed applying glyphosate foam at various concentrations to the foliage of crown vetch. As the amount of glyphosate applied per area increased above what I found to be the minimum effective dose, the growth of annuals/biennials progressively became more sparse and non-target perennial weeds were increasingly stunted. Differences in these plots and adjacent treated areas were noticeable for a few years.
Where foliar spraying of glyphosate is occurring, often what is selected for are resistant weeds like field bindweed and field thistle.
Does this mean one herbicide is better than the other? I would say "no." It depends on how it is used or misused. This is the reason it is important to conduct the trials Don Osmund outlines in this blog post. It is best to fail on a small scale in ruderal areas than cause a lot of damage to a high-quality natural area. It takes a lot of trials to refine a method so it will control the target weed while minimizing off-target damage.
UW-Madison has a series of free pdfs on invasive species management. They’re authored by Mark Renz a UW invasive species researcher.
ReplyDeleteThey cover the various methods and their efficacy. For instance, for buckthorn it says glyphosate on cut stump is 50-70% effective and triclopyr is 90-100% effective.
https://learningstore.extension.wisc.edu/products/management-of-invasive-plants-in-wisconsin-set-p1680
You provide a good example of a restoration challenge: how to move forward when evidence conflicts? I suspect most of these conflicts are due to site variability and also differences in application/assessment methods. My approach is to favor sources I personally know as high quality, sources that state all the relevant details of how they arrived at a conclusion (e.g. peer reviewed journals) and also my own experimentation.
DeleteMadison, WI has extremely hard water so if Renz didn’t use a water conditioner or softened water, that could account for his poor control. He states to apply herbicide within 1 hour of cutting so the question is how long did he wait in the experiment that yielded 50-70%. I had 100% kill waiting 1 hour in shady conditions with a small sample size but that may not apply to sunny conditions. The other question is whether he allowed enough time to see if the resprouts died or continued to grow. Without more details it’s hard to assess the quality of the Renz information.
I checked my sources on glyphosate effectiveness on common buckthorn:
1) a credible contractor who says it works fine
2) a credible comment from a forest preserve district employee that it isn’t consistent in winter or with plants >5 years old
3) a decent quality experiment (Restoration & Management Notes v20(4) p286) using only 10% glyphosate applied immediately to the stump at various sites in winter/early spring (canopy cover & buckthorn size not stated) that achieved 90-100% control.
4) My own experience of about 7 years for all size classes of buckthorn in shady environments & small to moderate size classes in sunny places at 2 different sites. I used 20% glyphosate in soft water in fall, winter & spring. I can’t recall ever seeing a resprout.
I missed the note at the end of the Panke/Renz document that says the information comes from land manager & researcher reports. So that adds another level of uncertainty regarding the quality of their sources. In addition, I just realized their minimum concentration of 20% Roundup (8% glyphosate) is way below what is used by most restorationists. So 70% effectiveness is probably a more accurate number for their summary, not 50%.
DeleteI apologize if I’m coming on too strong, but I feel it’s important to scrutinize restoration sources the same way as in other fields like engineering & medicine, to ensure we get the best results from our work in light of funding & personnel shortages. Thanks for submitting this source as this is how we all learn & hone our techniques.
I don’t think you’re coming off too strong, I just want to be sure glyphosate works as well as triclopyr if and when I use it more. I can foresee any resprouts being blamed on the effectiveness of glyphosate and when it comes to paid work that would be uncomfortable. I’ll keep the information you have provided to give anyone with questions.
ReplyDeleteMy main reason for wanting to switch to glyphosate is that bark oil isn’t readily available in Grant count wisconsin, it’s strange given there’s a handful of brands out there. I guess there’s no call for it. Everyone gets it from Nutrien agsolutions in deforest Wisconsin.
I used the term “bark oil” but entering "basal oil" into a search engine yielded some online suppliers. I didn't check if they have hoops to jump through like minimum orders, high shipping fees, business account required, etc. I've always worked for agencies that obtained herbicides for me.
DeleteIn the effort to eliminate a problem species (regardless of herbiciding with 10%, 50%, or even 100% concentration and with any initially observed associated kill rate up to 100%) follow-up is always required in the same area over not just one season but every year for many years until the pest is gone. Once and done would be nice, but Nature is not so accommodating. It is unrelenting follow-up that achieves success.
ReplyDeleteI completely agree & I’ll add that the more effective our chemical or mechanical control is, the less resources & time will be needed for that followup, giving us more time for other invasives, other management activities, expanding our management units or taking some needed breaks from the weed treadmill. That is less important for sites with lots of volunteers, few weeds or of small acreage, but even under those conditions, better effectiveness allows people to help at other sites, learn new skills like plant id or monitoring, mentor others, etc.
DeleteOn another topic, how long after black locusts are foliar spray can they me mowed?
ReplyDeleteHi, I’m interested in chemicals or combinations of chemicals (foliar spraying) that are effective on multiple species of invasives, for instance, buckthorn, honeysuckle and multiflora rose, crown vetch and parsnip.
ReplyDeleteAt work parties folks are invariably spraying other invasives than the target species and it would be great to know if it’s worthwhile or a waste of chemicals. For instance, we have crown vetch work parties where milestone is used, is spraying parsnip, and small woody invaders like multiflora rose and honeysuckle a waste? Should people be told only to spray the vetch or should another chemical be added to hit other species encountered?
Thanks,
Bob
I’m glad you’re thinking about ways to be efficient because that is how we make progress against the tough problem of invasives.
DeleteMilestone & Transline are persistent in the soil so they should be used only when necessary, such as on crown vetch, which is a hard to control plant.
It may be possible for one concentration of broadleaf herbicide to work for both herbaceous plants & foliar spray of woody plants. Using Garlon 4 as an example, the recommended herbaceous rate on the label is 1-4 quarts/acre. Using the 48 gallons/acre backpack sprayer calibration in my article (you should calibrate your own sprayer & use those numbers), that is 0.5 to 2% by volume in water. The recommended woody plant foliar rate is 4-8 quarts/acre so theoretically, 4 quarts/acre will work for both herbaceous & woody foliar. But foliar spray is subject to many variables that can cause poor control, meaning the minimum rate has a low chance of being effective. Some herbicides allow higher rates for spot spraying of herbaceous, so if the density of weeds falls into their definition, you may be able to spray at that higher rate. But then you are using an unnecessarily high concentration on herbaceous, which I try to avoid because we don’t yet know how herbicide affects underground fungal & bacterial networks. For example, 1 quart/acre Garlon 4 with 0.5% volume MSO adjuvant works fine for me on parsnip. Foliar requires your best people due to wind drift of relatively high concentration herbicide into the environment & on the applicator, so that may limit who can do both foliar & herbaceous treatment & which weather conditions are appropriate for it. Before risking off-target kill using foliar, I’d first run a year long experiment to verify the concentration used is effective on the species of interest.
I’m not big on mixing 2 different herbicides unless the label specifically says it’s ok. If they haven’t been formally tested together, it’s possible the mix could have negative environmental effects in the soil that is larger than the effect of either herbicide alone. Also, a 1 year experiment is necessary to know if a given mix is effective since one herbicide may antagonize the effects of the other herbicide.
Don, I’d like to see the chemicals you use for what species, concentrations, etc.
ReplyDeleteOr if someone has this information that you agree with.
I have the Wisconsin DNR’s, Rick Schulte’s from Nutrien Ag Solutions, UW-Madison Extension’s, one of the Illinois forest districts.
Can you go wrong with any of them?
Thanks,
Bob
I agree with your approach of assessing what other practitioners find effective. But if a list doesn’t state what the information is based on, I don’t use it. Some lists are just summaries of what is on the label or a mashup of variable quality reports. If it’s based on peer reviewed literature or field experience with details given, then I pay attention to it. Before putting a recommendation into practice, I read the label to make sure it is an acceptable herbicide in terms of persistence, volatility, species controlled, applicator safety, threat to nearby lakes/streams, etc.
DeleteConcentration is tricky because what works on one site may not work on another due to things like competition level & soil moisture/type (affects weed robustness). Also, practitioners don’t always assess effectiveness across varied growing season weather conditions. That’s why I emphasized doing your own 1 year controlled experiment during periods of reasonably normal climate & no burning so you’re confident all that hard work isn’t wasted. For parsnip, I flagged off 4 plots in a dense infestation with one as control (no herbicide) & the others 1, 2 & 2.9 quarts/acre Garlon 4/MSO. I assessed results by estimating % cover a year later. Always compare a recommended concentration with the label & reject that advice if it is outside the label limits. If a recommendation is stated as x% product by volume, it has to be considered an estimate. Nozzle type, sprayer model & operator technique affect the amount of product sprayed, so a recommendation should be given in product volume per acre using a calibrated sprayer.
I realize I’m complicating the decision, but these are the factors taught in state license training to protect the health of the environment, the public & the applicator. I think we should use the same standards whether licensed or not.
Here are some recommendations from myself & others for herbaceous weeds, based on field experience. Your mileage may vary & this list isn’t comprehensive nor necessarily the best solution. Assume the addition of methylated seed oil adjuvant per label & also assume softened water for glyphosate application. I had to omit many entries because the practitioner was exceeding the labeled rate.
https://www.nachusagrasslands.org/uploads/5/8/4/6/58466593/herbicides_for_various_weeds_2020-06.pdf
Bill is a good source.
Crown Vetch: 7 oz/acre Milestone (up to 14 oz/acre if less than 50% of an acre is treated). Follow the techniques given in my article.
Garlic Mustard: 1% Roundup Pro applied to 1st year rosettes in November & December. 2,4-D is not effective.
Purple Loosestrife: 1.5% Rodeo with Ortho 77 surfactant applied mid September.
Spotted Knapweed: 7 oz/acre Milestone or 10 to 22 oz/acre Transline.
Teasel: 4 quarts/acre Garlon 4 on rosettes. April/May application may be best.
Wild Parsnip & Burdock: 1 quart/acre Garlon 4 on rosettes, but since this is the low end of the label recommendation, it may be better to start with 2 quarts/acre & if desired, do an experiment to see if lower rates work.
Thanks for the information. I may have to copy and paste all of your information into a document I can refer to more easily than this post
ReplyDeleteDan, can I get your personal email? Or would you rather I pick your brain in this comment section? Bobcostanza@gmail.com
ReplyDeleteI’m the anonymous person, I’d use my name if I could figure out how to.
Thanks
Bob, I too have trouble with it. You might try using a different (I don’t even know the name for it) - examples being Safari, FireFox, GoogleChrome.
DeleteGenerally I compose the post through Safari but write responses to comments through GoogleChrome. But what works seems to change from time to time. I just go with it. (I suppose I would benefit from "a producer" or "web expert" or something.