Murdoch's Guide to Weed Control

We can’t control the weather or a plant’s readiness to absorb the chemical, but we can help you accurately control how much chemical you apply for the best results.

Calibrate for Accurate Herbicide Applications

An easy way to calibrate handguns for spot spraying:

One gallon of water equals 128 ounces
We will use a test area that is 1/128 of an acre
Now, we can calibrate using ounces of water collected to equal gallons per acre

Sprayer calibration tips for backpacks:

1-2 ounces of herbicide per gallon of water for 1-2% solution or rates of 1 pint/acre
3-4 ounces of herbicide per gallon of water for 3-4% solution or rates of 1 quart/acre

Here’s how it works:

Measure out an area that is 18.5’ x 18.5’
Spray the area while recording the time it takes to cover it
Using a measurable container, spray for the same amount of time that it took to spray the test site
The number of ounces collected equals the gallons per acre that you are spraying

Example:

We measured and sprayed our area. It took 51 seconds to spray it. Spraying into our container for 51 seconds, we collected 40 ounces of water. We now know we will be spraying at a rate of 40 gallons per acre. With this information, we can calculate our mixing rate. If a chemical calls for 2 quarts/acre, we divide 64 ounces (2 quarts) by 5,120 oz (40 gallons) to calculate ounces of chemical/gallons of water. In this case, it would be 64/5,120=.0125. If our sprayer is 14 gallons (1,792 ounces) we take 1,792 x .0125 = 22.4 or the number of ounces of chemical we need to mix with water into our 14-gallon tank.

ALWAYS READ THE PRODUCT LABEL FOR COMPLETE APPLICATION INSTRUCTIONS AND SAFETY INFORMATION. Follow label and stewardship guidelines to limit impact to non-target native forage species.

Boom Sprayer Calibration

Determine nozzle spacing.
Refer to the following chart to determine calibration course: +To determine the length of the calibration course for a nozzle spacing not listed, divide 340 by the spacing expressed in feet. Ex: Calibration distance for 19-inch nozzle spacing = 340 divided by 19/12 = 215 feet.
Measure and stake off the appropriate calibration course based on nozzle spacing. The course should be on the same type of ground as that to be sprayed (Speeds may be faster on roads than on sod, changing the application rate.).
Drive the course in the gear and rpm you will use when actually spraying. Record the time in seconds. Do this twice and average the time.
Park the tractor and maintain the same rpm.
Turn on the sprayer and catch the water from one nozzle for exactly the same number of seconds that it took to drive the calibration course.
Ounces caught = gallons per acre.
Check all nozzles. Flow rate should not vary more than 10% among all nozzles. Clean or replace any nozzles that do not fall in this range.

Nozzle Spacing	Length of Course
15"	272'
18"	227'
20"	204'
22"	186'
24"	170'

Boomless Sprayer Calibration

Measure effective swath width.
Refer to the following chart to determine calibration course: + To determine the length of the calibration course for a swath width not listed, divide 5,460 square feet (1/8 acre) by the swath width in feet. Ex: Calibration distance for 32-foot swath width = 5,460 divided by 32 = 171 feet
Drive the course in gear and rpm you will use when actually spraying. Record the time in seconds. Do this twice and average the time.
Park the tractor and maintain the same rpm.
Turn on the sprayer and use a trash bag and bucket to catch water for exactly the same number of seconds required to drive the calibration course.
Pints caught = gallons per acre.

+ Source Texas Agrilife Extension©

Nozzle Spacing	Length of Course
10"	546'
15"	364'
20"	273'
25"	218'
30"	182'
35"	157'
40"	136'

Weed Response to Pasture & Rangeland Herbicides

Application Guidelines for Herbicides Labeled for Range & Pasture

Vigilance to guidelines is necessary when applying herbicide on property foraged by beef and non-lactating dairy animals, horses, sheep, goats, and llamas.

*Lactating dairy animals do not graze or harvest green forage from treated areas until the next growing season. No restrictions for other grazing animals. ‡ No feeding or grazing restrictions if the application is 2 quarts liquid flowable; wait 8 weeks.

***May apply to low input hay i.e., dry land alfalfa and grass hay. Do not use on high-input hay that is irrigated and fertilized.

Chemical Application Rates & Tidbits

Herbicide	Rate Per Acre	Years of Control with One Application	Application Timing	Min Interval Between Application and Rainfall	Needs Surfactant	Storage Precautions
CHAPARRAL	1.5 to 3.3 oz.	3 to 4 years	Actively Growing Spring & Fall	4 to 6 hours	Yes	Store in dry place
MILESTONE or GRAZON NEXT HL	4-7 oz. 1.5-2 pints	3 to 4 years	Actively Growing Spring & Fall	4 hours	Yes	If allowed to freeze, warm container & shake before using
2, 4-D AMINE	2 to 4 pints	1 season	Actively Growing	4 to 6 hours	Yes	If allowed to freeze, warm container & shake before using
WEEDMASTER/ DICAMBA + 2, 4-D	1 to 4 pints	1 year	Spring	4+ hours	May improve performance	Store in dry place
ESCORT or CIMARRON PLUS	0.5 to 1 oz.	2 to 3 years	Actively Growing	4 to 6 hours	Yes	Store in dry place
ROUNDUP, GLYPHOSATE (kills all vegetation)	1 pint to 2 qts.	Emerged weeds	Actively Growing Spring	1 to 2 hours	May improve performance	Store above 10˚F
REJUVRA (controls annual grasses)	5 oz. (apply in 20 gal of water/acre)	3 to 4 years	May-August (apply in Sept & Oct if adding Plateau at 5 ozs./ac)	1 to 2 hours	No (shake jug prior to use)	Store in cool, dry place
DURACOR	16 to 20 oz.	3 to 4 years	Actively Growing Spring & Fall	2 hours	Yes	If allowed to freeze, warm container & shake before using

Disclaimer

Murdoch’s does not recommend using any residual herbicide on hay, silage, or hayledge that will be distributed, made available for sale, or moved off the farm or ranch where harvested.

Murdoch’s does not recommend using forage, straw, or manure from any herbicide treated area (including pasture) in compost or other garden amendments. Spread treated forage, straw or manure only on rangeland/pastureland, or non-susceptible crop areas.

Residual herbicide levels in manure and urine excreted from animals consuming treated forage (including pastureland) may contain enough herbicide residual to damage non-target plants. Herbicides cause no harm to grazing animals and pass through their digestive tract unchanged in three days. Provide three days of untreated forage before moving animals to sensitive crop areas.

For specific information and application directions, please read and follow the product label instructions or ask a Murdoch’s associate for help.

Information and recommendations by Murdochs's do not alter or replace the product manufacturer's specifications, including all product risks and warnings. Murdoch's does not guarantee any outcome and does not warrant against any harm caused by use of a product.