MSMA Herbicide on Johnsongrass (Application Guide)
MSMA may be used on johnsongrass only when the current product label and local registration allow that target and site. Confirm those details before buying or mixing. If use is allowed, follow the label for rate, timing, protective gear, weather limits, repeat treatments, cleanup, and disposal. There is no universal MSMA rate or safe off-label substitute.
The cheapest treatment is not always the lowest-cost option. A product that cannot legally be used on your site, or a spray that drifts onto desirable plants or toward water, can create far greater costs than the weed problem. I start with the label and the site, then decide whether spraying is an option at all.
Johnsongrass is a perennial grass. It can spread by seed and underground rhizomes, so one spray may not solve an established patch. The directions below help you check whether MSMA is allowed and, if so, prepare a careful application. They do not replace the label.
MSMA label verification, site eligibility, and safety preparation
This first check determines whether treatment is legal and suitable for your site. MSMA products can have different labels, and permitted uses can vary by product and location. Before you plan a spray, confirm the product’s current label, local registration, target weed, application site, method, and restrictions. If any point is unclear, do not apply.
Confirm the product, site, and target
MSMA is an arsenical herbicide. The label on the container is the controlling guide for that product and use. Do not assume a use is allowed because another MSMA product, a past label, or an online article describes it.
Read the full current label, including tables, footnotes, and supplemental directions. Check that it specifically permits all of the following:
- The intended site, such as the exact type of turf or other listed area
- Johnsongrass as a target
- Your planned application method
- The proposed application rate and any seasonal maximum
- The planned number of applications and minimum interval between them
- Any limits related to grazing, harvest, re-entry, or nearby areas
Check current registration with the relevant regulator or state pesticide authority as well. Rules can change. If the label does not authorize the site or johnsongrass, do not use MSMA there. Ask a licensed local adviser or extension service about legal alternatives.
Check the site and exposure risks
Walk the treatment area before mixing. Mark desirable plants, gardens, food or feed areas, surface water, drains, ditches, and other sensitive places. The label sets the required setbacks and drift limits; do not guess at a safe distance.
Also check whether the site is wet, sloped, or connected to a drain or waterway. Spray or rinsate that runs off can leave the treatment area. If wind, rain, or site conditions make it hard to keep the product on the labeled target, postpone treatment.
PPE and entry limits
Personal protective equipment, or PPE, means the clothing and gear the label requires to reduce exposure. Follow the exact directions for gloves, clothing, eye protection, and any respirator. Do not substitute ordinary work gear for label-required protection.
The label also sets re-entry requirements and may include worker-protection rules. Keep people and animals out for the stated period, and follow any posted-area or notification directions. If you cannot meet the label’s safety requirements, do not spray.
Johnsongrass treatment: labeled application procedure
Apply only after confirming that the product allows the site and target. Then follow its directions for weed growth stage, rate, water volume, weather, and application method. MSMA labels do not share one universal schedule, so a rate or interval from another product is not a safe shortcut.
Prepare the sprayer and mix
Use equipment approved for the labeled application. Inspect the tank, hoses, fittings, and nozzles for leaks or wear. Keep the sprayer dedicated to herbicide use when practical, or clean it exactly as the label directs before using it for other work.
Calibrate with water before adding herbicide. Calibration means checking how much spray the equipment applies over a known area. Mark a measured test area, spray it at a steady pace and pressure, then measure the water used. Repeat the test if the result varies. Use the label’s carrier-volume directions and adjust the equipment as needed.
Measure product and water accurately, and follow the label’s mixing order and water-quality directions. Use only a labeled rate. Do not add an unlisted tank mix or increase the dose because the johnsongrass looks tough. Do not mix more than you can use as directed.
Apply under label conditions
Treat johnsongrass only at the growth stage stated on the label. The label also controls wind, temperature, rainfast time, and other weather limits. If conditions are outside its directions, wait.
Use the labeled method and keep the spray on the target. Watch for drift toward people, desirable vegetation, food or feed areas, and water. Stop if wind shifts or if a leak, blocked nozzle, or other problem makes the application uneven. Do not exceed the label’s maximum rate, application count, or repeat interval.
What to expect after treatment
Do not judge control too soon or assume that browning means the entire patch is gone. Johnsongrass can regrow from underground rhizomes, and the label may allow a follow-up treatment only under stated conditions. Inspect the patch at the label’s stated assessment time, then compare what you see with its directions for repeat use.
Do not make an extra application just because control looks incomplete. First check the product’s permitted interval and seasonal limit. If the label does not allow another treatment, ask a qualified local adviser about other legal control options.
Sprayer calibration, cleanup, and application records
Careful calibration helps avoid over-application and wasted product. Cleanup matters just as much: follow the label for rinsing and rinsate disposal, and never discharge leftover spray or rinse water into a drain or waterway. Record the job so you can verify what was applied and when.
Calibrate by area, not guesswork
A small test with water can reveal uneven output before product is involved. Use a measured area and the same speed, pressure, and nozzle setup planned for treatment. Record the water used. If you change nozzles or operating conditions, repeat the check.
Only convert that result into a product amount if the label gives a rate and units that match your treated area. Double-check the area and units before mixing. If they do not match, ask a pesticide professional rather than improvising a conversion.
| Check | What to do | Why it matters |
|---|---|---|
| Output | Test with water over a measured area | Helps identify uneven or excessive spray |
| Product amount | Use only the current label’s rate and units | Avoids borrowing a rate from another formulation |
| Weather | Check label limits before and during work | Reduces drift and runoff risk |
| Follow-up | Check label interval and seasonal maximum | Prevents an unauthorized repeat treatment |
Clean equipment and manage rinsate
Follow the label’s cleaning steps, including any required rinse sequence. Rinsate is water that has contacted pesticide during rinsing. Handle and apply or dispose of it only as the label and local rules allow. Never pour it into a sink, storm drain, ditch, surface water, or other unapproved location.
Keep people and animals away during mixing and cleanup. Prevent back-siphoning when filling equipment, and do not leave an open container or sprayer where a spill can reach a drain or water source.
Keep a treatment record
Write down the product name and registration details, site, target, date, treated area, amount applied, weather, and applicator. Also note any required re-entry or grazing restrictions. These records help prevent accidental repeat applications and make it easier to discuss results with a licensed adviser.
Product storage, disposal, and seasonal planning
Safe storage and disposal are part of the treatment, not an afterthought. Keep the product in its original container and follow its label for storage conditions, spill response, and container disposal. Plan future control around the label’s limits rather than assuming you can spray again later.
Store the container securely, in its original packaging, and as directed on the label. Keep it away from children, animals, food, feed, and water. Do not transfer herbicide into a drink or food container.
Dispose of unused product and empty containers according to the label and local requirements. Do not burn containers or put leftover spray into household drains, roadside ditches, or waterways. If you are unsure how to handle a spill or unwanted product, contact the local pesticide authority or waste program for instructions.
For an established patch, track where johnsongrass returns and when treatment occurs. That record can help you plan inspections and avoid exceeding label limits. If MSMA is not permitted at your site, compare other legal options with a local extension office or licensed applicator. Do not use an unlisted product or method simply because the patch is difficult to control.
Illustrative field scenarios
These examples are planning situations, not reports of specific treatments. They show how the label check changes the next step.
| Situation | Decision |
|---|---|
| A land manager finds johnsongrass in a site that may be covered by a product label | Verify the current registration and every relevant label condition. If site and target are allowed, prepare and apply only as directed. |
| A homeowner finds johnsongrass in a lawn, garden edge, pasture, or near water | Do not assume MSMA is allowed there. Check the exact product label and local rules. If the site is not listed, do not apply. |
| A sprayer has leftover mixture after treating a patch | Follow label directions for any remaining spray and rinsate. Do not dump either into a drain, ditch, or waterway. |
Frequently asked questions
These short answers cover common decisions before and after treatment. The product label remains the final source for permitted sites, rates, application timing, protective gear, repeat treatments, re-entry, and disposal. When the label or local registration is uncertain, stop and seek qualified guidance.
Can I use MSMA on johnsongrass in my lawn?
Only if the current product label and local registration allow that specific lawn site and johnsongrass. Do not assume lawn use is permitted.
What rate of MSMA should I use?
Use only the rate on the current label for your exact product and site. There is no universal MSMA rate.
Can I use a rate I found for another MSMA product?
No. Formulation strength and directions can differ. Do not transfer a rate from another product or source.
When should I spray johnsongrass?
Follow the label’s directions for the target’s growth stage and weather. Do not rely on a general calendar date.
Can I spray again if the grass regrows?
Only if the label permits another application and its timing and seasonal limits are met. Regrowth alone does not authorize a repeat spray.
How long must people stay out of the treated area?
Follow the label’s re-entry interval and any worker-protection directions. The required time can depend on the product and use.
Can MSMA spray or rinsate go into a drain or ditch?
No. Do not discharge spray or rinsate into a drain, ditch, or waterway. Follow the label and local rules for handling it.
What if the label does not list my site or johnsongrass?
Do not apply the product there. Contact a local pesticide authority, extension service, or licensed applicator for legal options.
What should I record after treatment?
Record the product, site, target, treated area, rate, date, weather, and applicator. Note re-entry and other label restrictions as well.
(This article was written by one of our staff writers, Victor Dempsey. Visit our Meet the Team page.)
