Herbicide Application - Mix/Pacing question.

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drg777
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Herbicide Application - Mix/Pacing question.

Post by drg777 » July 4th, 2017, 6:18 pm

Hi all,

I'm spraying herbicide on my lawn for the first time. From what I gather summer isn't the best time to spray, but I'm trying to get started on nearly a decade a lawn neglect, so I'm gonna give it a go now and then put down preemergent next spring. I was hoping someone could confirm that my math is correct for the current application I'm planning. I really don't want to fry my lawn.

I'm using Ortho weed-b-gon in a 1 gallon pump sprayer. My yard is approximately 2,500 sq feet. The instructions indicate 2.5oz of concentrate for a gallon of water, per 400 sq feet.

Am I correct that that means I should be going though a whole gallon of the mix (2.5oz of concentrate and 1 gallon of water) for every 400 sq feet? Totaling approximately 15oz of concentrate across the entire lawn?

I ask because I did a test run with just water in the sprayer , to get a feel for the pacing, and it took nearly 20 minutes to use the gallon across 400 sq feet. It seemed like the pace was much slower and the application heavier than any video footage I've seen.

Does this seem ok, or am I miscalculating something?

Thanks.

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ken-n-nancy
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Re: Herbicide Application - Mix/Pacing question.

Post by ken-n-nancy » July 4th, 2017, 8:04 pm

drg777 wrote:
July 4th, 2017, 6:18 pm
Hi all,

I'm spraying herbicide on my lawn for the first time. From what I gather summer isn't the best time to spray, but I'm trying to get started on nearly a decade a lawn neglect, so I'm gonna give it a go now and then put down preemergent next spring. I was hoping someone could confirm that my math is correct for the current application I'm planning. I really don't want to fry my lawn.

I'm using Ortho weed-b-gon in a 1 gallon pump sprayer. My yard is approximately 2,500 sq feet. The instructions indicate 2.5oz of concentrate for a gallon of water, per 400 sq feet.

Am I correct that that means I should be going though a whole gallon of the mix (2.5oz of concentrate and 1 gallon of water) for every 400 sq feet? Totaling approximately 15oz of concentrate across the entire lawn?

I ask because I did a test run with just water in the sprayer , to get a feel for the pacing, and it took nearly 20 minutes to use the gallon across 400 sq feet. It seemed like the pace was much slower and the application heavier than any video footage I've seen.

Does this seem ok, or am I miscalculating something?

Thanks.
First off, welcome to the "Around The Yard" lawn forums. Although it's not the ideal time to be spraying for weeds, one has to start somewhen. If your results are not as effective as you desire, don't give up on it; if the weeds don't all get killed from the current application, a weed control application at the end of August will be more fruitful.

Secondly, congrats on applying a liquid weed killer instead of a granular "weed-n-feed" product. The sprayed liquid products are much more effective, and also result in less wasted herbicide in the environment.

Yes, you are understanding the label directions correctly. You've done exactly the right thing to figure out your pacing and coverage.

Personally, what I do when applying a herbicide is determine the amount of product to put in the water to deliver the same amount of weed killer per sq foot (or ksqft) as on the label directions, but in the amount of water that my sprayer wants to deliver.

I've found by performing "test sprays" of plain water in my driveway that my handheld sprayer delivers about 1 gallon of water per 1000 sq feet at the rate I walk, height I hold the sprayer, width of my spray, etc. Accordingly, I then put the amount of product in 1 gallon of water that is intended to cover 1000 square feet. One needs to realize that there is always a risk when deviating from label directions. Since my application rate of 1 gallon to 1000 square feet is less water per sqft than the Ortho Weed-B-Gon product, the concentration of the herbicide in the water is higher in my sprayer than that recommended on the label, meaning that the effect of any mistakes I make by spilling herbicide or spraying too heavily will be worse than if I had exactly followed the instructions on the label. This is a judgment call you'll ultimately have to make for yourself -- if you do something wrong and kill off your lawn, it's your fault, not that of the manufacturer.

I would suggest putting 1 gallon of water in your sprayer, and then spraying in your driveway (to practice your technique and pace to cover the driveway evenly without excessive overlap). Measure how much area you covered in your spraying. You then know how many square feet will be covered with 1 gallon of water via your sprayer and spraying technique. (You may have already done this and just not posted the results in your initial posting.)

You then need to figure out how many ounces of product you need to add to that 1 gallon of water to get the rate of product per square foot (or ksqft) listed on the label.

You've already done much of the math, determining that at a rate of 2.5oz of concentrate for 400 square feet, you'll need ~15oz of concentrate for your 2500 square foot lawn.

If you'd like help with the math (or just want folks here to double check it for you), go ahead and post how many square feet are covered by 1 gallon of water from your sprayer using your spraying technique, and we can help.

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andy10917
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Re: Herbicide Application - Mix/Pacing question.

Post by andy10917 » July 4th, 2017, 9:54 pm

Make sure also to read the label carefully for any restrictions on weed killers above 80/85/90 degrees.

drg77
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Re: Herbicide Application - Mix/Pacing question.

Post by drg77 » July 6th, 2017, 12:12 pm

Thanks a bunch for the welcome, all. I really appreciate your time.

I did some test runs with water in the pump sprayer.
It takes 1/4 gallon to get what I think is sufficient coverage across 400 sq feet. So I'm 3/4 of a gallon under what the label suggests. If I used the whole gallon over 400 sq feet I'm pretty sure I'd be moving at a snail's pace and saturating the soil, not just coating the weed leafs.

So if that pacing/coverage is adequate I'm guessing I'd need four times the recommended 2.5 oz concentrate (10 ounces) per gallon? Since I'm only using 1/4 gallon of the mix per 400 sq feet.

If this is accurate then 1 gallon with 10 ounces of concentrate would cover 1600 sq feet. So I would need an application of 1 gallon/10oz followed by a 1/2 gallon/5oz Which would allow me to cover approximately 2400 sq feet, just under the total sq footage of my lawn.

Does this make sense?
Would it be safer if I held back an ounce or two of concentrate from the total mixture (to reduce chances of any major lawn damage) or might I run the risk of not laying down an effective dose of the herbicide?

Fronta1
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Re: Herbicide Application - Mix/Pacing question.

Post by Fronta1 » July 13th, 2017, 2:10 am

ken-n-nancy wrote:
July 4th, 2017, 8:04 pm
I've found by performing "test sprays" of plain water in my driveway that my handheld sprayer delivers about 1 gallon of water per 1000 sq feet at the rate I walk, height I hold the sprayer, width of my spray, etc.
I'm curious about this as well, may I ask what your rate of walk, height you hold, and width of spray are? Thanks.

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