Professionals Review Herbicide Spray Nozzles

We asked 13 invasive plant management specialists for their insight on nozzle selection and maintenance based on their field experience. The following information summarizes tips and recommendations from commercial and governmental herbicide applicators.

Backpack Sprayers

What type and size of nozzle is best?

Most applicators said they use flat fan, off-center flat spray*, or adjustable cone spray tips in backpack sprayers; two applicators also use handguns (e.g., Green Garde; rollover hand gun) with their backpack sprayer.

*Off-Center spray tips are commonly installed in swivel nozzle bodies. Because these bodies are adjustable for angular position, a wide spray swath is easily obtained.

Tips and Recommendations

  • Nozzles with a wide angle and larger droplet size increase coverage and reduce drift.
  • The type of nozzle (e.g. flat fan, off-center) is less important than making sure the output is consistent and the applicator is calibrated for that particular sprayer/nozzle.
  • Nozzle construction (brass, high-quality plastic, or stainless steel) is less critical than maintaining and replacing nozzles regularly.
  • An Off-center (OC)-12 nozzle on a backpack sprayer can be calibrated to provide similar output (Gallons Per Acre or gpa) as truck-mounted sprayers; thus, backpacks can be refilled from the truck spray tank in the field, minimizing mixing and loading for backpack sprayers.
  • Off-center (OC)-04 and -06 nozzles apply about 7 and 10 gpa respectively at 3 miles per hour (mph) with about a 4-foot swath width, allowing an applicator to treat a larger area before having to refill backpack.

Boomless Spray Nozzles for ATV/UTV or Truck Spray Platforms

What type of nozzle works best?

Applicators reported using either Boom Buster (27%) or Boominator boomless nozzles (73%) for their all-terrain vehicle or truck-mounted sprayers. Respondents operate nozzles between 30 and 50 psi; with 30 psi most commonly recommended.

Tips and Recommendations

  • Both Boom Buster and Boominator nozzles operated at 30 psi pressure offer good coverage, droplet size and water use (Table 1).
  • Boom Buster nozzles work well, but the small plastic fin in the crease is easily scuffed when cleaning or unclogging the nozzle. A little nick can make a big difference in spray pattern.
  • Model #125 Boom Busters work well for ATVs driven at speeds up to 7 mph, and Model #187 Boom Busters work well on truck-mounted equipment (Table 1).
  • Model #1250 (R/L) Boominator is used on ATV/UTV sprayers with ground speeds up to 7 mph; Model #1870 (R/L) has higher output and can be operated at ground speed up to 12 mph. Boominator nozzles #1255 (L&R) and 1871 (L&R) have a 5 and 10 foot spray width respectively, and can be used to treat narrow road rights of way and trails.


Hand Guns

What type and nozzles work best?

The majority of applicators said they use hand guns in their invasive plant management program; however, some were concerned about difficulty in applying accurate rates. Green Garde JD9-C hand guns are used by more than 50 percent of the survey respondents followed by Intellispray, Hudson GES 505, and TeeJet Model 403.

Tips and Recommendations

  • “Intellispray handgun has an adjustable output but consistent application rates are difficult to achieve. They also have an O-ring that must be replaced after about 1.5 field seasons, and are almost impossible to replace correctly. Replacement parts are difficult to find in rural areas.”
  • “The Green Garde handgun has a squeezable trigger that cannot be made to apply a consistent output. Therefore, it is nearly impossible to calibrate because the output (GPA) varies depending on how hard you squeeze the trigger.”
  • “In my experience, spray output with handguns is around 40 GPA, which is a lot of water/herbicide solution per acre. Most problems involving over-application have been the result of handgun application.”
  • “I calibrate Green Garde JD9-C handgun to a set pressure, either 30 psi or 75 psi, and a set coverage pattern, and I’ve been happy with the results.”
  • “The medium tip (2-5 gpm) on the Green Garde handgun reduces refill time and the output is similar to that of the boomless nozzle, so we can switch back and forth more easily [between broadcast and spot spraying] if needed.
  • The large tip (3-8 gpm) on Green Garde JD9-C may reduce spray drift in high wind areas.
  • “We have used both the Green Garde JD9-C ($167) and the GES-505 ($94) economy hand gun. The JD9-C is re-buildable where the GES is not. For nearly twice the price, I am not convinced the JD9-C is worth the cost. I have pretty much gone to the GES and been satisfied with the performance”.

Nozzle Replacement

How often should you change spray nozzles on your equipment?

Applicators agreed that nozzles should be checked and/or calibrated at least once a year and replaced if worn, damaged, or output is 10 percent over or under the manufacturer’s standard.

Tips and Recommendations:

  • Calibrate periodically throughout the season and replace the nozzle if output begins to vary.
  • Check nozzles using a digital flow calibrator about once a month throughout the spray season and replace nozzles with flow rates measuring 10 percent greater or less than manufacturers standards.
  • Although some applicators recommend replacing backpack sprayer nozzles annually, most replace on an as-needed basis.

Other general comments from professional applicators

  • “Calibration is the key to applying the correct amount of herbicide to a given area and is operator specific. Use a marker dye to help keep application rates consistent and prevent over application.”
  • “In order to maintain optimal equipment performance, triple rinse the sprayers after each project has been completed. This ensures rubber O-rings and filters are not destroyed or plugged up by debris and chemical residues.”
  • One respondent commented that he virtually eliminated leaking problems with backpack sprayers by liberally applying 100% pure silicone grease to O-rings and rubber parts.

Thank you to the following individuals who contributed to this article:
  • Amy Adler, Rosebud County Weed Coordinator, MT
  • Dave Brink, Mineral County MSU Extension, MT
  • Bryce Christiaens, Missoula County Weed District, MT
  • Morgan Levi, US Fish and Wildlife Service, MT
  • Rod Litzel, Johnson County Weed and Pest District, WY
  • Gary Olsen, Wheatland County Weed Coordinator, MT
  • Nick Holden, Mountain Valley Plant Management, MT
  • Kenny Keever, Bureau of Land Management, MT
  • Matt Kennedy, NPS-Glacier National Park, MT
  • Lee Shambeau, 4 Control Inc. WI
  • Steve Tyrrel, Integrated Ag Services, Inc., MT
  • Jessica Zarate, US Fish and Wildlife Service, MT
  • Travis Ziehl, Teton County Weed and Pest District, WY