BAYER CROPSCIENCE SUBMISSION

APPLICATION METHODS AND UTILITY OF SULFONYLUREA

HERBICIDES IN NON‐CROP, RANGELAND, AND FORESTRY AREAS

MARCH 2016

Bayer CropScience LP

2 TW Alexander Drive

RTP, NC 27709
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APPLICATION METHODS AND UTILITY OF SULFONYLUREA HERBICIDES

IN NON-CROP, RANGELAND, AND FORESTRY AREAS

Harvey A. Holt, Ph.D.

Professor Emeritus, Purdue University

Seattle, WA 98146

holth@purdue.edu

Page

Rights-of-way .................................................................................................................................. 3

Right-of-Way Resource ....................................................................................................... 4

Roadside.............................................................................................................................. 6

Safety Recovery Zone (Clear Zone)......................................................................... 6

Sign Visibility ........................................................................................................... 6

Sight Distance.......................................................................................................... 7

Drainage Enhancement and Ditches....................................................................... 7

Road Surface Degradation ...................................................................................... 8

Snow Drift Control .................................................................................................. 8

Fire Hazard Reduction............................................................................................. 8

Appearance............................................................................................................. 8

Guide Rails .............................................................................................................. 9

Median Barriers ...................................................................................................... 9

Sign Posts and Delineators.................................................................................... 10

Fences ................................................................................................................... 10

Structures, Abutments, Headwalls and Inlets ...................................................... 10

Storage Yards........................................................................................................ 10

Road Shoulders..................................................................................................... 10

Curbs, Gutters and Median Islands....................................................................... 11

Broadleaf Weeds................................................................................................... 11

Special Grass Control ............................................................................................ 11

Electric Utility.................................................................................................................... 12

Conductor Clearance ............................................................................................ 12

Structures.............................................................................................................. 13

Emergency Line Service ........................................................................................ 13

Substations and Storage Yards ............................................................................. 13

Railroads............................................................................................................................ 13

Yards...................................................................................................................... 13

Bridges .................................................................................................................. 14

Line-of-Road.......................................................................................................... 14
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Road Crossings...................................................................................................... 15

Brush Control ........................................................................................................ 15

Pipelines............................................................................................................................ 16

Right-of-Way ......................................................................................................... 16

Pumping Stations.................................................................................................. 16

Summary ........................................................................................................................... 16

Rangeland ..................................................................................................................................... 17

Forestry ......................................................................................................................................... 18

Noxious Weeds............................................................................................................................. 19

Herbicide Application Equipment................................................................................................. 20

Broadcast Liquid Application ............................................................................................ 20

Boom with Conventional Tips............................................................................... 20

Regular Flat Fan ........................................................................................ 20

Flooding Flat Fan....................................................................................... 20

Whirl-Chamber Nozzle.............................................................................. 21

Rain Drop .................................................................................................. 21

Boomless Spraying ................................................................................................ 21

Off-Center Nozzle...................................................................................... 22

Boom-Buster Nozzle ................................................................................. 22

Straight Stream Nozzle.............................................................................. 22

Radiarc ...................................................................................................... 23

Directa-Spra .............................................................................................. 23

Directed Liquid Application............................................................................................... 24

Handgun................................................................................................................ 24

Backpack Sprayer.................................................................................................. 24

Dual Spray Gunjet ................................................................................................. 25

Aerial Application.............................................................................................................. 26

Micro-Foil Boom ................................................................................................... 26

Thru-Valve Boom (TVB)......................................................................................... 26

Summary ........................................................................................................................... 27

Role of Specific SU Herbicides ...................................................................................................... 27

The Realities of Buffers................................................................................................................. 27

Appropriate Ways............................................................................................................. 28

Appropriate Equipment.................................................................................................... 29

Knowledgeable Applicators.............................................................................................. 30

Summary ....................................................................................................................................... 31

References .................................................................................................................................... 31

Acknowledgements....................................................................................................................... 32
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Credentials.................................................................................................................................... 33
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THE USE AND BENEFITS OF SULFONYLUREA HERBICIDES

Harvey A. Holt, Ph.D.

Professor Emeritus, Purdue University

Seattle, WA 98146

holth@purdue.edu

When the sulfonylurea (SU) herbicides entered the market in the 1980’s, they revolutionized 

non-crop use. Sulfometuron-methyl, metsulfuron-methyl and chlorsulfuron had a special fit in 

non-crop uses. First, weed control was better. In an application industry that lives on 

guaranteed contracts, no one is going to pass on improved weed control, regardless of specific 

objective. The perennial weed bouncing bet (Saponaria officinalis) was a common occurrence 

on railroads. It literally disappeared after sulfometuron-methyl use. Second, the ability for 4 

ounces of sulfometuron-methyl to replace 6-8 pounds of simazine + 6-8 pounds of diuron was 

fantastic on so many levels. The obvious thought is reducing the environmental load of 

herbicide. Ounces replaced pounds. Operationally, applicators that haul their herbicides on 

their trucks could literally haul more acres of products before reloading. Applicators using large 

tanks spent less time because opening a jug took less time than opening bags and bags. 

Applicators using small tanks had to find new ways to measure very small amounts of a 

herbicide. Because the products were priced per ounce, proper sprayer calibration was 

especially critical and precise application became the prime objective. That the new herbicides 

were incredibly active at low rates meant that drift control was imperative. The application 

industry accepted, adapted, and embraced these new products because their advantages 

greatly exceeded their potential issues.

Objectives of this document are to educate on current application technology; educate on the 

importance of IVM and ROW vegetation management; and to highlight the importance of SUs 

to IVM across the non-crop markets. The document will discuss the general areas of non-crop 

vegetation management in which SUs play a role. For example, SUs are not used for tree 

injection so this practice will not be discussed.

RIGHTS-OF-WAY

The nation’s rights-of-way (ROW) provide a major conduit for the flow of goods and services 

vital to the American economy. Major ROW include lands set aside for roadside, electric utility, 

railroad, and pipelines, and total more than 60 million vegetative acres across the country

(Table 1). Since ROW are related to supplies and services for people, most ROW acres are 

located in the heavily populated eastern U.S. ROW in eastern U.S., that area east of the 

Mississippi River, are located in a climatic zone favorable for vegetation growth. Generally 

adequate rainfall throughout the growing season and warm temperatures serve to enhance 

weed growth and reduce prolonged herbicide control. In the absence of any control program 
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hardwood tree species would become the dominant vegetation on the ROW. Northern conifers 

are prevalent in the the northeast and lake states; southern pine and mixed hardwoods in the south and 

southeast. These two regions are separated by the Central Hardwood region. Tall grass and short grass 

prairies dominate the states of the Central 

Plains. Trees mostly occur along water 

courses. The Rocky Mountains has its 

compliment of woody species, but tree 

growth tends to be slow. West of the Rocky 

Mountain tends to be semi-arid to arid 

except along the west coast and particulary 

the far corner of the Pacific Northwest 

where abundant rain makes for rapidly 

growing trees and other vegetation. (Figure 

1)

Reliability and public safety are major 

concerns across all ROW. The ROW must 

allow workers to perform their function without hazards to those that use and depend on 

them. Unlike other use sites, mismanagement of vegetation on ROW can have drastic and fatal 

effects on peoples’ lives.

RIGHT-OF-WAY RESOURCE

Rights-of-way are corridors that traverse a continuous array of properties, ownerships, 

topography, and adjacent crops. Generally speaking, only railroads and highways actually own 

the ROW. Electric utilities and pipeline companies generally have easements to access, manage 

and maintain the ROW and the infrastructure on 

it. 

Table 1 illustrates the scope and magnitude of 

vegetative acres in ROW of the U.S. ROW are 

most impacted by the imposition of buffers 

because a ROW is essentially a very narrow strip 

of land. Table 1 lists the distance to the edge of 

the ROW. Imposing a 25 ft buffer on any ROW 25 

ft wide or less would preclude the use of any SU 

herbicide on that ROW. It’s not just a buffer. It 

actually impacts the vegetation management 

on literally millions of acres (Figure 2). The tragic 

part is that the buffer alters the management 

on rural county roads, which, according to the 

Figure 1. Vegetation zones of the U.S.

Figure 2. The vegetative area for county roads is 

so narrow that any buffer effectively eliminates 

the SU herbicide from the programs of the 

greatest number of roadside miles.
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Dept. of Transportation, “in an era where we’ve seen a 25% decline in roadway fatalities over 

the past 10 years, far too many deaths are still occurring on the roads” managed by county 

governments.

Table 1. Vegetative ROW acres based on widths for major ROW types. (ROW sources listed in 

Reference section)

ROW Type

(Date of data)

ROW 

Width (ft)

Vegetation 

Width (ft)

Distance to 

ROW edge (ft)

US Total 

(miles)

US Total

(vegetation 

acres)

Railroad (2012) 1001 100 50 138,524 1,679,079

Highway – rural2(2015)

Interstate, freeways,

& expressways 300 2523 126 34,561 1,055,681

Principal &

minor arterials 75 514 26.5 222,974 1,378,199

Major & minor

collectors 50 265 13 668,8000 2,107,733

Local 50 266 13 2,049,049 6,457,609

Oil pipelines (2013) 50 50 25

Crude 50 50 25 49,974 302,873

Product 50 50 25 87,452 530,012

Gas pipelines (2013)

Distribution mains 20 20 10 1,255,035 3,042,509

Transmission 50 50 25 302,777 1,835,012

Gathering lines 20 20 10 17,369 42,107

Electric transmission (private utilities)

(structure miles)7(1974)

<31 KV 40 40 20 7,622 36,955

31-50 KV 50 50 25 397,885 2,411,424

51-131 KV 75 75 37.5 1,259,473 11,449,755

132-188 KV 110 110 55 752,480 10,033,067

189-253 KV 125 125 62.5 487,381 7,384,561

254-400 KV 150 150 75 332,636 6,047,927

401-600 KV 180 180 90 193,244 4,216,233

601-850 KV 225 225 112.5 46,500 1,268,182

Grand Total: 61,278,918

 

1 ROW width based on discussions with railroad applicators.

2 ROW width currently based on discussions with DOT personnel from IN and MD, and FHA personnel.

3 Excludes two lanes, each 24 ft wide.

4 Excludes a 24 ft road

5 Excludes a 24 ft road

6 ROW width based on consultation with county noxious weed coordinators. 

7 ROW widths made in consultation with electric utility and other knowledgeable personnel. The ROW of agencies 

such as TVA and BPA are not included.
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ROADSIDE

Maintaining the nation's roadside ROW, the areas between the edge of the pavement and the 

outside ROW boundary, focuses on safe travel for the motoring public. These areas may be 

either constructed or natural, and they may include the median strips on multilane highways 

and interchange areas. Roadside vegetation is controlled for 1) safety concerns, 2) road 

structure maintenance, and 3) appearance or beauty. Historically, the following roadside sites 

were managed manually or mechanically. Herbicides proved to be more effective at less cost. 

The array of alternative herbicide treatments presented by the family of SU herbicides 

enhanced the chemical option.

Safety Recovery Zone (Clear Zone)

Vehicles need a safe place to stop when they accidentally leave the road. This area is called the 

safety recovery zone or clear zone. Roads designed for higher traffic speed and density have 

wider safety recovery zones than roads designed for slower speeds and less traffic (Figure 3). 

Cut slopes require narrower safety recovery 

zones than do flat areas. Steep fills require the 

widest safety recovery zones. Since many vehicles 

continue on to the bottom of steep slopes, a clear 

area beyond the edge of the slope is desirable.

Trees are the major vegetation problem in the 

safety recovery zone. Trees are the single greatest 

cause of fatalities from vehicle collisions with 

fixed objects. Individual state policies differ on 

the size and height of trees permitted in the 

recovery zone, ranging from no trees allowed at 

all to trees allowed that are less than four inches 

in diameter at one foot above ground. 

Sign Visibility

Signs along roadsides must be visible regardless of 

season, time of day, or weather conditions (Figure 

4). Signs convey warnings, guidance, and 

information. They are an important part of road 

safety, and can prevent accidents and driver 

confusion. Hidden signs are a safety hazard 

because their message is obscured. Undesired 

vegetation can be near the sign or between the sign and the point where the driver should see 

the sign. 

Figure 3. The safety recovery zone is an integral 

part of the highway design.

Figure 4. Signs need to be visible for traffic 

safety and driving convenience.
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 Sight Distance

The length of road visible to the driver is the sight 

distance. Clear sight distance is needed for 

stopping and for making decisions about turning, 

changing lanes, passing, and entering the 

roadway. As speed increases, greater sight 

distance is needed. Vegetation has its greatest 

effect on sight distance on two-lane, rural 

highways. Vegetation can block sight distance at 

intersections and across curves (Figure 5).

Depth perception on the right side of the vehicle is 

difficult for many drivers. Vegetation encroaching 

from the shoulders often forces or subtly directs 

drivers to the center of the road on two-lane 

highways. This can reduce driver safety. Encroaching vegetation affects driver behavior most 

when weeds occur in short, isolated sections. Tall vegetation and overgrown shrubs should be 

kept far enough from the roadside so as not to influence driver behavior.

Drainage Enhancement and Ditches

Vegetation growing on the road shoulder can slow water from draining off the road. Water on 

the road surface can cause automobile hydroplaning or become ice patches in winter. Water 

that does not run off the road often collects or runs down the pavement. The flowing water 

gathers force and eventually breaks over the edge. The increased water pressure causes 

erosion of the shoulder at that point. Weed dams are a particular problem under guide rails 

where machine grading is not possible, but herbicide treatment is. Weeds growing around or 

over inlets can slow water drainage. The area around drainage inlets should be kept free of 

weeds.

Drainage ditches in eastern U.S. are usually managed in a selective manner, i.e., woody plants 

are controlled while leaving grass cover. Woody plants and other plants that catch debris and 

restrict water flow are the main problem in these ditches. Low-growing grass is desirable 

because it controls erosion, and it minimizing interference with flowing water. Grass buffers 

can also act as biofilters by trapping sediment. Vegetation control promotes rapid drainage 

and often improves the appearance of the ditch.

Sometimes roadside drainage ditches are maintained weed free to facilitate rapid water 

movement after storms, particularly in western U.S. The presence of vegetation slows water 

Figure 5. The encroaching trees obstruct 

vision across the curve for motorists on the 

roadway and prevent snow melt.
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flow and traps soil in the ditch. Over time the ditches accumulate soil that must be 

mechanically removed to maintain the ditch. Residual soil active herbicides are applied on 

these drainage ditches during dry periods. 

Road Surface Degradation

Water can speed the degradation of pavement and road surfaces, soften and reduce the 

supporting ability of subgrades and shoulders. Weeds can destroy paved shoulders by growing 

through cracks and accelerating deterioration. Once established in the crack where the 

shoulder meets the road surface, roots or creeping rhizomes can punch through the road 

surface. The surface of roads shaded by trees dries slower, and ice and snow take longer to 

melt. Water reduces the life of the surface, especially asphalt.

Snow Drift Control

Snowdrifts occur on the downwind side of any obstacle that slows the wind. Tall vegetation, 

either trees or weeds, can cause drifts as the snow piles up behind the vegetation. Fences, 

barriers, median plantings, and guide rails clogged with weeds or overgrown with vines can 

cause snow to drift. Narrow bands of vegetation upwind from the road and downwind from 

wide-open spaces increase snowdrifts on the road. Since an obstacle has an influence distance 

of 15-20 times its height, vegetation some distance from the roadside may require control in 

areas susceptible to snow drifting.

Fire Hazard Reduction

Hot catalytic converters and mufflers can ignite 

dry vegetation. In western U.S. where annual 

grasses such as wild oats and cheatgrass

complete their life cycle with the onset of 

drought, weed-free areas wider than the normal 

road shoulders are maintained so vehicles can 

pull off the road without risk of igniting a fire 

(Figure 6).

Appearance

Figure 6. Roadside fires can be serious problems 

when invasive grasses mature.
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Roadsides are highly visible to the public. 

Vegetation management enhances the 

appearance of the roadside and gives the road a 

definite delineation to motorists (Figure 7). Their 

appearance varies from rough turf to manicured 

lawns and from planted flowers to native 

vegetation. Managing roadsides to meet the 

requirements of native vegetation can maintain 

their dominance. When roadside vegetation 

management meets the functional requirements 

for transportation (safety recovery, sight distance, 

sign visibility), improved appearance can be a lowcost fringe benefit.

Guide Rails

Guide rails prevent cars from leaving the road where adequate recovery space is not available. 

They are a visual warning to the motorist to be alert. Weeds must be controlled to ensure that 

guide rails are seen by motorists and inspected by maintenance personnel (Figure 8). Weeds 

growing around the guide rails also hold moisture, which causes the guide rails to rust. Guide 

rails are usually established in asphalt, gravel, or grass. Aggregates and winter-applied abrasives 

tend to accumulate under guide rails. These materials hold moisture that degrades the asphalt 

and promotes weed growth. Also, weeds grow in 

the crevices around the guide-rail support posts 

when they are set in asphalt. Guide rails can be 

treated with a variety of techniques, such as a 

handgun, a Radiarc, a short boom with nozzles 

spraying each side of the guide rail, flood nozzles, 

or off-center nozzles treating in front of and 

under the guide rail.

Median Barriers

Median barriers prevent traffic from crossing into 

on-coming lanes. Median barriers catch and 

accumulate aggregates and abrasives that 

support weed growth (Figure 9). Herbicides are 

applied with a variety of methods including 

Figure 7. Vegetation management improves 

appearance and road delineation.

Figure 8. Guide rails need to be seen by 

motorists as well as maintenance inspectors.

Figure 9. Weeds will grow in the aggregate that 

accumulates at the base of median barriers.
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handguns, off-center, or straight stream nozzles. Treatments are commonly only spot 

applications. 
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 Signposts and Delineators

Like guide rails, signposts and delineators are 

anchored in soil or asphalt. They are also subject 

to rusting caused by weeds. Mowing next to 

these types of obstructions is not possible. 

Removal of weeds with a nonselective herbicide 

treatment in an area around the posts large 

enough to overlap with mowers is usually done 

with handguns (Figure 10).

Fences

Mowing around or next to fences is difficult. The 

ideal control is a banded residual weed control 

treatment (Figure 11). Weeds near fences are 

commonly treated with handguns or backpack 

sprayers.

Structures, Abutments, Headwalls, and Inlets

Vegetation degrades abutments and headwalls. 

However, mowing around them is troublesome. 

Weed control around drain inlets is necessary for 

visibility and drainage maintenance. Usually 

herbicides are applied with handguns or 

backpack sprayers. Care must be taken not to 

spray into the drain itself.

Storage Yards

Weed control in storage yards provides a safe work area, enables workers to find parts and 

supplies when needed, and reduces equipment deterioration. Weed control with herbicides is 

commonly used because obstructions make mowing difficult, especially in areas other than 

the alleyways. If size permits, broadcast herbicide application equipment can be used in 

combination with handguns for inaccessible areas. Granular and pelleted formulations are 

convenient to use in storage yards.

Road Shoulders

Total vegetation control eliminates the deteriorating effect of weeds growing through the edge 

of the asphalt. It provides a clear area for motorists to stop, and it reduces the risk of fire 

(Figure 12). Weeds growing through the shoulder loosen the soil. A weed free shoulder stays 

Figure 10. Total vegetation control around 

delineator posts facilitates mowing. 

Figure 11. Weed control under fences reduces 

maintenance costs.
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compacted, making it safer for vehicles to stop 

and start. Maintaining a compacted shoulder 

reduces soil erosion and the need for mechanical

grading operations to smooth and dress the 

shoulder area. A nonselective herbicide treatment 

is used for maintaining this weed-free zone 

without disturbing the shoulder. In most cases, 

shoulder treatments are applied with a moving 

vehicle equipped to treat the shoulder area; 

Radiarc, Boom-Buster, or small OC nozzle.

Curbs, Gutters, and Median Islands

Curbs, gutters, and median islands have a variety 

of surface materials, including soil, concrete, 

asphalt, gravel, or brick. The non-soil surfaces 

have cracks where weeds can grow (Figure 13). 

Weeds attract litter and harbor rodents. A 

herbicide treatment is applied to these cracks and 

crevices to prevent weed growth, and is usually 

applied with a backpack or handgun.

Broadleaf Weeds

The presence of tall growing broadleaf weeds gives the roadside an unkempt appearance. 

Control of these weeds is the major effort of many vegetation management programs. 

Broadleaf weed control can be done throughout the growing season. If treatments are 

conducted in the spring while the weeds are small and hidden by the grass, the results will be 

less noticeable. Fall applications are effective for controlling germinating winter annuals and 

biennials in the rosette stage. Treatments to control broadleaf weeds can be applied as a spot 

or a broadcast treatment by a variety of methods, including boom and boomless spray 

equipment. 

Special Grass Control

Special grass-control programs include Johnsongrass, fescue, or wild oat control, and 

Bermudagrass release. Controlling one grass species in another grass can sometimes be 

accomplished by 1) careful control of application rate or treatment timing, 2) using directed 

application, or 3) taking advantage of the difference in plant heights. These treatments are 

applied by broadcast, spot, or wiping equipment. 

Figure 12. Vegetation on the road shoulder 

increases maintenance problems.

Figure 13. Cracks and crevices support 

vegetation on roadsides.
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ELECTRIC UTILITY

Electric utilities control vegetation to keep electricity flowing through the conductors, promote 

public safety, allow inspection of the infrastructure, insure emergency access, and maintain 

equipment operation.

Conductor Clearance

Conductor clearance around an electrical transmission 

line is at the heart of vegetation control for a utility. 

Transmission lines carry electricity from generation 

source to substation and substation to substation. 

Unlike distribution lines transmission voltages are 

measured in thousands of volts (KV), personal contact 

is fatal, and contact with vegetation causes regional 

blackouts. While tall growing trees are usually 

considered to be major culprits, the relative height of 

the tree to the conductor is more important (Figure 

14). Transmission lines sag under load, the lines sway 

in wind, and the arcing distance increases with 

increase voltage. Consequently, as transmission voltage 

increases poles or towers become taller, insulators become longer, and the ROW increases in width. 

While trees at mid-span are usually of concern, as transmission lines cross undulating terrain the short 

tree on the ridge may be a more serious issue than the tall tree in the valley. Mismanagement of 

vegetation on a transmission line is likely a career altering event for the person in charge.

All ROW managers in the eastern U.S. and the Pacific Northwest contend with trees. Trees 

also occur in other regions of the U.S., but are notably sparser or slower growing. Usually the 

objective is to selectively control some trees. Typically, control is directed at the tall woody 

species with the goal of releasing lower growing vegetation that will occupy the site and 

hinder tree species establishment. Because of their size, woody plants can be treated 

individually or collectively, and in a number of ways. The SU herbicides used for woody plant 

control are applied to the foliage.

Foliar applications are an easy way to control dense stands of woody plants. The largest 

selection of herbicides is available for this method of control. These applications can be made 

with a hose and handgun for spot or broadcast treatments, or other broadcast equipment. 

The brown foliage that results from many herbicide treatments (brownout), particularly for 

tall trees, may create a visual problem for the public. Brown foliage on small trees is not as 

noticeable. When brush control treatments are applied in late summer or early fall, the brown 

foliage blends better with natural leaf senescence.

Figure 14. Because transmission line sag under 

load and sway in the wind, structure height and 

ROW width increase as voltage increases.
15

Structures

Both wooden and steel structures should be free of vegetation so structures and insulators can 

be inspected for preventative maintenance. Inspection can be done from helicopter or ground 

surveillance. 

Emergency Line Service

Electric transmission ROW need to be free of large vegetation so crews have access to sites for 

emergency line service. Lines free of overhanging 

vegetation are less likely to be taken down by

limbs falling during storms.

Substations and Storage Yards

Total weed control is important in substations and 

storage yards (Figure 15). Vegetation poses a fire 

hazard, harbors insect pests and rodents, disrupts 

the equipment in substations, and is an aesthetic 

problem. It is important to keep these areas weed 

free to prevent tripping and falling when 

employees are working with the electrified 

equipment.

RAILROADS

Railroads need to control vegetation for the similar reasons as electric utilities and roadsides. 

The areas of control fall into five broad groups: yards, bridges, line-of-road, road crossings, and 

brush. 

Yards

Weed control in yards is done to provide the safe 

work place required by the Federal Railroad 

Administration (FRA); to prevent fires around 

buildings and storage sites; to prevent wheel 

slippage; to facilitate maintenance and 

inspection; and to improve appearance (Figure 

16). Railroad yard treatments use residual soil 

active herbicides applied early in the growing 

season to prevent weed and grass growth around 

yards, switches, buildings, and storage areas. 

Long-term vegetation control is desired. The 

equipment most often used is a fixed boom 

sprayer equipped with flat fan, Boom-Buster or off-center nozzles mounted on a hi-rail truck.

Figure 16. Vegetation in yards is a serious hazard 

to railroad employees.

Figure 15. Substations are kept weed free for 

employee safety and fire hazard reduction.
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Boom-Buster and off-center (OC) nozzles are used to supplement the fixed boom in order to 

treat adjacent tracks in a single pass. A hand-held spray gun may be needed around buildings or 

on “stub” tracks and other areas inaccessible to a track mounted vehicle.

Bridges

Vegetation control around bridges, especially 

wooden bridges, is necessary to reduce fire 

hazard and to facilitate structure inspection and 

maintenance (Figure 17). Railroad bridge 

treatments involve the use of residual soil active 

herbicides applied early in the growing season to 

prevent vegetative growth around the supports 

of wooden bridges. Vegetation control for the 

length of the growing season is desired. 

Line-of-Road

The line-of-road phase of railroad vegetation 

control refers to main lines and branch lines, as 

well as signals and structures along the tracks. It 

usually has the greatest number of treated acres 

compared to the other phases of railroad 

vegetation management (Figure 18). Vegetation 

control is needed to protect the roadbed by 

maintaining proper drainage, to allow track 

inspection, to improve visibility, and working of 

signals, switches, signs, and crossings, and to 

reduce fire hazard along the ROW. Line-of-road 

operations usually require a 

postemergence treatment for shortterm weed control. Weeds are 

present when the treatment is 

made and new weeds may begin 

growing before a killing frost. The 

equipment usually used is the same 

as that used in the yard treatment --

a hi-rail truck or spray train usually 

equipped with fixed booms and 

Boom-Buster nozzles (Figure 19).

Figure 17. Vegetation around wooden bridges 

is a serious fire hazard.

Figure 18. Vegetation control in roadway 

ballast preserves ties and track stability.

Figure 19. Hi-rail trucks are used to treat line-of-road, yards, and 

bridges.
17

Most line-of-road is treated as a spot treatment only at areas where weeds are growing. The 

four feet on each side of the tracks at the edge of the ballast (the toe path) is the only part 

that is generally treated continuously. Most railroads a monitored for weed presence at least 

twice in the growing season. The second application is focused on weed escapes and vines 

encroaching from the ROW edge.

Road Crossings

Road crossing treatments are applied to the 

areas on either side of highway grade crossings

to improve visibility and comply with state legal 

requirements by both the automobile and the 

train engineer (Figure 20). Road crossing 

treatments are usually applied after weeds have 

emerged, and are usually intended to suppress 

the vegetation on the railroad right-of-way 

rather than to eliminate it. Because track time 

is so critical and often limited and road crossing 

are readily accessible by road, crossing treatments tend to be conducted by special crews with 

a variety of hand equipment and an array of herbicides to apply the most effective treatment to 

the vegetation, which can vary by quadrant of the road crossing.

Brush Control

Brush control is necessary to maintain visibility around signs, signals, and crossings. Brush 

control is for clearance to keep woody plants from encroaching and striking railcars or 

employees as they pass (Figures 21a, 21b). Woody plant control is generally on a 3-4-year cycle

Figure 20. Both trains and traffic need to be 

seen at road crossings.

Figure 21a. Brush control prevents limbs from hitting 

railcars and employees.

Figure 21b. Brownout resulting from chemical side 

trimming to reduce encroachment.
18

and is a major program in eastern U.S. The brush treatments amount to side trimming to 

reduce encroachment. The brown foliage can be managed by herbicide selection and timing of 

application.

PIPELINES

Right-of Way

Vegetation management issues for pipelines 

parallels electric utilities in many respects. 

Vegetation control on the pipeline ROW is 

necessary for inspection, access, and safety. 

ROW free of brush can be inspected to find

warning signs of leaks (Figure 22). Open ROW

enable crews to conduct maintenance and 

emergency repairs. Total vegetation control 

around pumping stations and storage tanks is 

important for reducing fire hazard.

Pumping Stations

Season long vegetation control is necessary in 

pumping stations for fire hazard reduction and 

facility reliability (Figure 23). Handgun 

applications are most common around the actual 

equipment and facilities. Some areas with 

substantial open ground can be treated with 

short booms on light trucks or all-terrain vehicles.

SUMMARY

Rights-of-way vegetation management is necessary for adequate safety, infrastructure 

maintenance, and improved appearance. All contribute to safe and reliable operations. 

Vegetation management performed for fire prevention, employee and public safety, facilities 

inspection, as well as noxious weed law compliance, are important for all ROW. The goals 

remain the same – protect people, move goods and services, and protect the environment.

Figure 22. Brush control on pipelines is necessary 

for leak inspection and maintenance.

Figure 23. Total vegetation control is imperative at 

pumping stations.
19

RANGELAND

Range and grassland pasture is perhaps the largest land use area in the U.S.; approximately 587 

million acres (Lubowski, Vesterby, Bucholtz et.al., 2006) (Figure 24). Most is controlled by federal 

agencies; particularly the Bureau of Land Management. Range improvement is largely a matter of 

controlling undesired weeds, of which most fall in the legal category of “noxious weeds”. 

Legally, a noxious weed is any plant designated a federal, state, or county government to be 

injurious to public health, agriculture, recreation, wildlife, or any public or private property. The 

list maybe defined at the state or even the county level. Each government entity can define the 

nature of control that should be or must be applied to that weed’s occurrence. 

Most of our rangeland weeds originated in Europe or Asia and were introduced to the western 

ranges in the nineteenth century. Without their native controls of insects, pathogens, and 

herbivores these weeds dominate the U.S. native plants and can create large monocultures. 

These monocultures can increase wind and water erosion, decrease capture, storage, and 

proper release of rainfall, as well as alter nutrient cycling. These monocultures reduce biological 

diversity by displacing the fauna that depend on the native plants for habitat and food. The 

grazing capacity of weed-infested land can be reduced by up to 75% (Sheley, Petroff, and 

Bormann, 1998).

Once non-indigenous plants become established, they are usually permanent in ecological time 

and very difficult to manage (Coblentz, 1990). Developing a noxious weed control program 

requires using a combination of methods to limit weed encroachment (Sheley, Manoukian and 

Marks, 1999). Such methods include:

 Limiting weed seed dispersal

 Containing neighboring weed infestations

 Minimizing soil disturbance

Figure 24. The range resource encompasses millions of acres. The sagebrush on the left is critical habitat for the 

sage grouse; the annual grass on the right depletes soil moisture and become a fire hazard.
20

 Detecting and eradicating weed introductions early

 Establishing competitive grasses

 Properly managing grasses

None of these principles involve buffers. Buffers are counterproductive to controlling noxious 

weeds.

FORESTRY

The U.S. forest resource covers about 517 million 

acres (Lubowski, Vesterby, Bucholtz et.al., 2006). The 

conifer regions (about 300 million acres) of southern 

and southeastern U.S., the Pacific Northwest, the 

Lake States, and northeast are the areas of major 

industry ownership and the most intensive culture 

These are the areas of greatest herbicide use for site 

preparation (Figure 25), plantation establishment 

(Figure 26), and conifer release (Figure 27). 

Applications are made from the ground or aerially.

The Central Hardwood region (approximately 

125 million acres) between the conifer regions of 

eastern U.S. is characterized by private ownership. The primary herbicide use is banded treatments to 

establish newly planted seedlings (Figures 28 and 29)

Competition control before planting or at planting results in increased height and diameter growth of 

pine seedlings until crown closure. In studys duplicated in Texas, Mississippi, and South Carolina all 

Figure 25. Site preparation controls vegetation 

left on site after harvest.

Figure 26. Herbicide applied at edges of planting 

bed for residual control.

Figure 28. Herbicides banded at planting gives 

seedlings site resources to become established.

Figure 27. A

release conife

and related p

Figure 29. Directed herbicide gives selectivity for 

plantation release.
21

treatments containing sulfometuron-methyl had greater height and diameter growth than untreated 

plots (Ezell, A.W., J.L. Yeiser and L.R. Nelson, 2013).

NOXIOUS WEEDS

Most rights-of-way managers are confronted with “noxious weeds.” Many states have declared 

certain plants to be "noxious weeds" because they have a detrimental effect on public health, 

agricultural crops, natural ecosystem function, or animal production. State law may require 

their control. If the agency or company responsible for the property does not control these 

weeds, local governments can contract the work to an outside group and charge the negligent 

party.

Noxious weeds earn their notoriety not just by reducing grazing and related Animal Unit 

Months. Also included in the array of their undesirable characteristics:

Toxic to horses, cattle, pigs, humans

Seed awns cause injury to nose and eyes 

of grazing animals

Dense stands crowd out native 

vegetation

Deplete soil moisture early

Liver damage when ingested

Contact with sap causes severe 

dermatitis on people

Spread seeds by tumbling

Degrades wildlife habitat

Causes birth defects

Climbing growth smothers trees

Causes abortions

Creates impenetrable barrier

Causes tainted milk

Causes photo-sensitization when grazed

There are serious reasons why noxious weeds have that designation. The idea of only 

controlling some of them because they are too close to the edge of the field is incongruous. 

HERBICIDE APPLICATION EQUIPMENT

Applications of the sulfonylurea (SU) herbicides are made in a liquid form. All liquid spray 

equipment has unique advantages and disadvantages. Most are usually operated at low 

pressures, less than 40 psi at the spray tip.

BROADCAST LIQUID APPLICATION

Boom sprayers are used for broadcast applications of herbicides. The boom is equipped with a 

row of similar nozzles that break the spray solution into small drops and distribute the spray in 

a specific pattern. Nozzle performance depends on nozzle type, tip design, operating pressure, 

size of the opening, discharge angle, speed, and distance of nozzle from the target.

Boom with Conventional Tips
22

Regular Flat Fan

The regular flat fan (Figure 30) is the most 

commonly used nozzle for boom application of 

liquid sprays. The regular flat fan tip makes a 

narrow oval pattern with tapered edges. It is 

used for broadcast applications at 15 - 40 psi. 

Fan spray angle is the angle between the edges 

of the spray pattern. Tips are available with fan 

spray angles of 25, 50, 65, 73, 80, and 110 

degrees. The nozzles are usually spaced 12 - 20 

inches apart on the boom. Boom applications are particularly useful over railroad ballast. To 

prevent drift typical nozzle tips are 80 degrees or less and apply one gallon or more per minute 

(8010, 8015, 8020), which is about 2X the usual agriculture nozzle tip.

Flooding Flat Fan Nozzle

A flooding flat fan nozzle delivers a wide-angle 

flat spray pattern, 115-125 degrees. It also 

operates at low pressure and produces large 

spray droplets (Figure 31). Droplet distribution 

is fairly uniform across the pattern, but is not as 

even as the pattern of a regular flat fan nozzle. 

Tips should be tilted 45 degrees for broadcast 

spraying. The recommended nozzle spacing is 40 

inches. These nozzles should have 100% overlap 

so the width of the spray pattern on the ground 

is twice as wide as the nozzle spacing. Boom height should be adjusted until this overlap is 

achieved.

Whirl-Chamber Nozzle

The side-entry hollow cone or "whirl-chamber" 

nozzle produces a very wide angle, hollow cone 

spray pattern at very low pressures (Figure 32). It 

has a large opening and resists clogging. Because 

of the wide spray angle, the boom can be 

operated close to the ground, thus reducing 

drift. Spacing for double coverage and angling 15 

Figure 30. Regular flat fan nozzles used to treat 

railroad ballast.

Figure 31. Widely spaced flood tips with 100% 

overlap.

Figure 32. Side-entry hollow cone nozzles 

should be angled to the rear rather than 

pointing straight down.
23

to 45 degrees to the rear is recommended for uniform application. 

Rain Drop®

The Rain Drop nozzle produces a hollow-cone pattern and large droplets for drift control. 

Although the pattern is similar to the whirl-chamber tip, this nozzle contains a secondary 

chamber where the swirling action of the spray solution further reduces small droplets (Figure 

33). The spray angle varies from 80-100 degrees depending on disc-core combination in the 

nozzle. The nozzle should be angled 30-45 degrees from horizontal to obtain uniform 

distribution when used for broadcast application. This nozzle is generally used at 20-40 psi. 

These nozzles should also have 100% overlap and this boom height should be adjusted until this 

overlap is achieved.

Boomless Spraying

Boomless spraying enables the application 

equipment to stay on the tracks or roadside and 

spray areas off the side of the equipment. This 

results in a more uniform speed and rate of 

application as well as faster speed. Obstructions 

can interrupt the spray pattern but do not 

interfere with boomless spray application as 

much as with a boom application. Even though 

this equipment is usually mounted on the side of 

the application equipment, it can also be 

attached to the end of a boom to spray a wider 

swath or a greater distance from the equipment.

Off-Center Nozzle

Off-center (OC) nozzle tips produce a flat fan 

spray pattern with the nozzle at the side rather 

than over the center of the pattern (Figure 34). 

OC nozzles are used either without a boom or 

at the end of booms to extend the effective 

swath width. The ability to treat a wide swath, 

the variety of sizes available to alter swath 

width and gallons applied per acre, the ease of 

mounting, and the low cost all contribute to 

the popularity of these nozzles. Coverage can 

be variable because air turbulence distorts the 

Figure 33. The Rain Drop® was one of the 

first nozzles designed for reducing spray drift.

Figure 34. An OC nozzle (at the end of the 

boom) is often used to extend the swath width 

of a spray boom.
24

spray pattern as it leaves the nozzles. They are 

usually permanently mounted to the

application equipment at a height that gives a 

specific desired swath width. Drift control 

additives can be used with these nozzles.

Boom-Buster® Nozzle

The Boom-Buster nozzle is a straight stream diffuse nozzle. The spray solution is split by a nylon

vane and forms a fan pattern very similar to the OC nozzle (Figure 35). The Boom-Buster nozzle 

produces larger droplets than a regular OC nozzle and has replaced much of the OC nozzle use.

The Boom-Buster spray pattern is more stable than the OC pattern. The nozzle has all of the 

same uses as the OC nozzle.

Straight Stream Nozzle

Straight stream nozzles produce a solid stream pattern like water flowing from a pipe. These 

nozzles are used to spray a distant or specific target. For right-of-way application, they are most 

commonly used as a cluster of nozzles (Figure 36). Each part of the cluster is set to treat a 

defined section of the right-of-way. A nutation action breaks the solid stream into large

droplets. Swath width is adjusted by turning specific nozzles or sets of nozzles in the cluster off 

or on.

Radiarc®

Figure 35. The Boom Buster® is used in place 

of an OC nozzle.

Figure 36. Straight stream nozzles are used to 

treat a swath to the side of the sprayer. 

Oscillating the spray tips breaks the streams 

into drops.
25

The Radiarc is a group of straight stream tips aligned in a single plane like the fingers of a hand 

(Figure 37a and 37b). It uses an oscillating motion to mechanically break up the streams of 

spray solution. Swath width is adjusted by plugging selected tips. A Radiarc can be mounted to 

spray either a horizontal or vertical spray pattern. It can be adjusted to treat a swath from 4-25 

feet wide. Uniform spray pattern is obtained by altering the sizes of the tips.

Directa-Spra®

The Directa-Spra also uses straight stream nozzles. The units are fitted at the factory to spray an 

arc of 90, 180 or 360 degrees; 180 degrees is the most common. The nozzle clusters rotate 

around the center point (Figure 38). Swath widths from 10-25 feet and applications of 25-50 

gallons per acre are obtainable

Figure 37a. A close-up view of the 

Radiarc®

Figure 37b. The spray pattern of a Radiarc®. 

Figure 38. The Directa-Spra® controls drift by 

using clusters of straight stream tips.
26

DIRECTED LIQUID APPLICATION

Handgun

The handgun is a common and versatile type of 

spray equipment. It is used to treat accessible 

and inaccessible sites with spot and broadcast 

treatments. The handgun is attached to a hose 

that in turn is attached, through the pump, to 

any size tank holding the herbicide mixture. The 

handgun is usually adjustable to change the 

spray pattern from a solid stream to a wide cone 

pattern (Figure 39). Pump capacity 

(gallons/minute), hose diameter, and hose 

length limit the distance the applicator can move 

from the sprayer. The handgun is usually used for 

high-volume applications, generally more than 

100 gallons of solution per acre. When equipped 

with off-center tips, it can be used as a boomless

sprayer for low-volume application, or for spot 

treatments (Figure 40). All types of liquid 

formulations and drift control products can be 

applied.

Backpack Sprayer

A backpack sprayer is a self-contained unit (tank 

and pump) carried on the back of the applicator 

(Figure 41). The capacity of these sprayers is

usually less than 5 gallons. A mechanical agitator 

plate may be attached to the pump plunger. The 

entire tank may be pressurized or only a small

chamber that draws from the main tank. This 

equipment is useful for selective applications and 

spot treatments. Backpack sprayers are very 

adaptable to a wide range of nozzle 

configurations – short booms, Boom-Busters, 

adjustable cone nozzles, swivel tips, and rollover 

Figure 39. The handgun is a versatile piece of 

equipment.

Figure 41. The backpack sprayer is quiet and 

very efficient when treating low numbers of 

stems per acre or treating bands.

Figure 40. Treating noxious weeds made easy

with the adaptability of the handgun.
27

nozzles for treating individual plants. This sprayer is versatile, quite, relatively inexpensive, and 

unobtrusive. Consequently, it is the major way of treating many acres on many types of ROW. 

Applications made from backpacks are obviously a very targeted application

Dual Spray Gunjet®

The dual spray Gunjet (Figure 42) has been particularly useful for treating individual foliage with 

backpack sprayers but is adaptable to all types of sprayers. The traditional Gunjet is fitted with 

a unique roll-over valve that accommodates two spray tips with different volumes and different 

patterns, e.g., 6503 and 4003. Only the selected tip operates. A particular spray tip can be 

immediately switched to another by rotating the selector to the desired tip. A typically set up 

would include a very narrow fan tip, about 15 degrees, and the other is a wider even fan tip, 

e.g., 0 - 65degrees. A hollow cone adjustable tip 

also works in this set-up.

Figure 42. The two different nozzles enable 

the applicator to treat weeds close and at a 

distance by easily switching to the second 

nozzle.
28

AERIAL APPLICATION

Just as the application industry has created and adapted special equipment to control drift from 

ground applications, it has developed special 

equipment to control drift from aerial 

applications.

Micro-Foil Boom

The Micro-Foil boom was developed primarily for 

use by helicopters. It has been the dominant piece 

of equipment used for spraying electric ROW. 

Each nozzle is an airfoil shape on the leading edge 

with a row of straight stream nozzles on the back 

edge (Figure 44). The herbicide solution is sprayed 

into still air. The solution falls to the ground as a 

wet curtain (Figure 45).

Thru-Valve Boom (TVB)

The TVB® is a precision application device which

enables herbicide application accurately, 

uniformly and on target. The TVB® was developed 

to enable operators of fixed-wing aircraft to apply 

herbicides quickly and accurately (Figure 46). 

However, the TVB allows helicopter and fixedwing applicators to apply herbicides sprays to 

forests, rangeland, and utility rights-of-way on 

target and at the desired rate (Figure 47).

The TVB® will produce particles free of aerosol at 

speeds of 100 to 180 mph and greater. At low 

airspeeds up to 20 mph, these droplets simply 

spread out to form a swath and fall to the 

ground by gravity to give a uniform spray pattern 

on the ground. At higher speeds of 50 to 180 

mph, the forward motion of these droplets is 

sufficient to make them unstable. With minimal 

shear action, the droplets tend to flatten out 

from the continued forward motion and form 

"donut" shaped droplets with 

essentially no aerosol, allowing for the spraying 

of herbicides from helicopters and fixed-wing 

Figure 44. The individual nozzles of the MicroFoil boom.

Figure 45. The spray pattern of a Micro-Foil 

boom.

Figure 46. Spray pattern of a TVB.
29

aircraft with greatly reduced risk of injury to 

non-target vegetation.

SUMMARY

There is an array of equipment available for applying herbicides. Each is designed for specific 

application situations. Although low pressure and large drops are a common characteristic, the 

applicator controls the quality of the results.

ROLE OF SPECIFIC SU HERBICIDES

The vast array of weed control situations that fall in the general area of non-crop means there 

is a role for several SU herbicides. Historically, sulfometuron-methyl (Oust XP) has been the 

primary product for total vegetation control with residual soil activity for railroads, road 

shoulders, and electric substations and pumping stations. At lower rates Oust and Oust Extra 

are the major herbicides for selective uses in conifer and hardwood forestry. Metsulfuronmethyl (Escort XP) has a major role in woody plant control critical to electric and roadside sites. 

Chlorsulfuron (Telar XP) is especially effective on controlling broadleaf weeds and releasing 

grass species in pasture, range, and noxious weeds on all non-crop sites. These herbicides are 

also components of numerous premixes; e.g., Landmark, Oustar, Oust Extra, Pastora, 

Perspective, Throttle, Viewpoint, and Westar.

THE REALITIES OF BUFFERS

1. Buffers do not improve weed control. If the ability to use the most effective herbicide is 

restricted the end result can be less than desired.

2. Buffers do not improve drift control. Buffers have nothing to do with drop size.

3. Buffers do not make applicators better. All commercial applicators are certified and 

licensed by state programs that have been approved by EPA.

4. Buffers are contrary to the concepts of Integrated Vegetation Management Programs.

The precepts of IVM require all treatment options be available for consideration.

Figure 47. Helicopter equipped with a TVB.
30

5. Buffers are in conflict with the legal requirements of states to control noxious weeds.

State laws require the landowner to control noxious weeds across their property. Having 

to leave a buffer of uncontrolled noxious weeds is in conflict with state law and 

maintains a source of reinvasion, which negates any control efforts. 

The SU herbicides are not the first highly efficacious products to enter the market. The 

application industry has adapted and used these products safely for more than a quarter of a 

century. The extreme activity is the characteristic that influences their use. Their activity is 

analogous to the use of toxic products. There is no hazard with a very toxic product if there is 

no exposure. A very active herbicide does not pose a hazard to off-site plants if the herbicide 

never gets there. And there are years of experience to prove that herbicides such as 

sulfometuron, metsulfuron and chlorsulfuron can be and have been used without disastrous 

off-target results. This is because the products have been applied in appropriate ways and with 

appropriate equipment by a cadre of well trained and knowledgeable applicators.

Appropriate Ways

These ways include the professional ways of avoiding herbicide drift and movement, which are 

already on the product labels, such as Oust XP. 

 Do not spray when the product cannot be kept to the site. Wind speed is most critical.

 Do not spray when wind is blowing toward sensitive crops/plants/sites. Herbicides will 

not drift upwind.

 Do not make applications to natural or man-made bodies of water such as lakes, 

reservoirs, ponds, streams and canals.

 Do not apply if prevailing local conditions may be expected to result in off-site 

movement and cause damage to neighboring desirable vegetation or agricultural crops.

 The user must read and understand all label directions, precautions, and restrictions.

 Leave treated soil undisturbed to reduce the potential for herbicide movement by soil 

erosion due to wind or water.

 Do not apply in or on irrigation ditches or canals including their outer banks.

 Injury to or loss may occur if equipment is drained or flushed on or near desirable trees 

or other plants or in locations where the chemical may be washed or move into contact 

with their roots.

 Treatment of powdery, dry soil or light, sandy soil when there is little likelihood of 

rainfall soon after treatment may result in off target movement and possible damage to 

susceptible crops when soil particles are moved by wind or water.

 Applications may not be made to soil that is subject to wind erosion when less than a 

60% chance of rainfall is predicted to occur in the treatment area within 48 hours.

 Applications made where runoff water flows onto agricultural land may injure crops.
31

 Application made during periods of intense rainfall, to soils saturated with water, 

surfaces pave with materials such as asphalt or concrete, or soil through which rainfall 

will not readily penetrate may result in runoff. 

 Do not treat frozen or snow covered soil.

 Be sure the sprayer is calibrated before use. 

 Avoid overlapping and shut off spray booms while starting, turning, slowing or stopping 

to avoid injury to desire species.

 Avoiding spray drift is the responsibility of the applicator.

 The most effective drift management strategy is to apply the largest droplets which are 

consistent with pest control objectives.

 Drift potential is lowest when applications are made in light to gentle sustained winds 

(2-10 mph), which are blowing in a constant direction. 

 Avoid gusty or windless conditions.

 Drift potential is high during a surface temperature inversion.

 Making applications when there is a sustained wind moving away from adjacent 

sensitive areas (e.g., residential areas, bodies of water, known habitat for threatened or 

endangered species, non-target crops) is an effective way to minimize the effect of 

spray drift.

 Using product compatible drift control additives can reduce drift potential.

 When applications are made in a crosswind the swath will be displaced downwind.

 Applications with wind speeds greater than 10 mph are prohibited.

 Applications into temperature inversions are prohibited.

 Apply spray as the lowed height that is consistent with pest control objectives.

 Applications must be made using equipment delivering an extremely coarse or coarser 

droplet size spectrum as defined by ASABE S572.1 

There is also the operational practice of spraying parallel to the stream border or bank as the 

applicator approaches water to avoid spraying into the water.

Appropriate Equipment

ROW applicators have always dealt with the issue of drift and have developed equipment and 

practices that are worlds apart from the typical agricultural crop use situation. If you browse 

through a Spraying Systems catalogue, you will note that most of the nozzles have spray angles 

greater than 80 degrees; 110 degrees is probably most common. Also most of the nozzle top 

out at 0.5 to 0.8 gallons per minute. More common nozzles in railroad applications apply at 

least one gallon per minute (Table 2). 
32

Table 2. Examples of nozzle and tip sizes used by commercial 

applicators treating ROWs.

Nozzle Type Output @ 40 psi 

(gallons/minute)

Spraying Systems 6510 1.0

Spraying Systems 8010 1.0

Spraying Systems 8015 1.5

Spraying Systems 8020 2.0

Spraying Systems 4040 4.0

Delavan Raindrop RA-30NY 140 3.0

Boom Buster 180-6 4.3

Boom Buster 375 16.7

Boom Buster 437 21.5

OC 40 17

OC 150 15

StreamJet 0010 1

StreamJet 0015 1.5

Knowledgeable Applicators

These herbicides are not present in the consumer market. Being present only the professional 

applicator arena means that the products are being applied by or under the supervision of a 

state licensed applicator. Each state, as per EPA mandate, licenses commercial applicators. 

Licensure requires, in all states, certification and certification is obtained by examination. Every 

state exam contains questions about drift. Every state has an annual weed conference or 

vegetation management association, and nearly every program has topics on pesticide drift; 

causes, problems, and prevention. Every state DOT has in-house or external continuing 

education programs. All application companies conduct training programs because no one 

wants to be paying for injured crops or plants. The application industry that services railroads 

has their own annual initial training and continuing education conference that always has a 

topic on drift.
33

SUMMARY

 SU’s are a very effective class of herbicides that are critically important for managing 

undesirable vegetation in Industrial, Forestry, Range and Pasture settings. 

 The general diversity of SU products available is important to provide efficient and 

effective control.

 Controlling vegetation is important for protecting infrastructure and maintaining a safe 

transportation system such as railways and roadways, as well as ensuring the reliable 

and safe flow of utilities through electric transmission lines and gas/oil pipelines. 

 SU’s are important for controlling invasive and noxious weeds in Range and Pasture 

areas in order to maximize grazing and forage production to optimize food production. 

 Many SU’s can be safely used over grasses which are important for reducing erosion and 

important for wildlife habitat restoration and protection such as in rangeland areas and 

utility rights of way. 

 Many SU’s can be applied safety around trees and are essential tools for vegetation 

management in forestry production. 

 Specific SU’s provide control of weeds where no other product can provide selectively. 

 SU’s are a very cost effective family of herbicides which helps reduce the cost of 

maintaining public and private lands

 Additional buffers that do not take into account vegetation management practices 

would render these products non-usable 

REFERENCES

Coblentz, B.E. 1990. Exotic organisms: a dilemma for conservation biology. Bio. Cons. 4:261-65.

Ezell, A.W., J.L. Yeiser, L.R. Nelson. 2013. Fifth-year pine growth response to woody release 

treatments in young loblolly plantations. Pages 223-225 in J.M. Guldin, editor, Proceedings 

of the 15th Biennial Southern Silvicultural Research Conference. Hot Springs, AR. e-Gen. 

Tech. Rep. SRS-GTR- 175. Asheville, NC: USDA, Forest Service, Southern Research Station.

Holt, H.A., F. Whitford, J.M. Di Tomaso, et. al. 2002. Model Certification Training Manual for 

Right-of-Way Pesticide Applicators. https://www.agriculture.purdue.edu/pesp/rowmanual/
34

Miller, J.H., S.T. Manning, and S.F. Enloe. 2013 (slightly revised 2015). A Management Guide for 

Invasive Plants in Southern Forests. Gen. Tech. Rep. SRS-131. Asheville, NC. USDA, USFS, Sout. 

For. Res. Stat. 120 pg.

Panter, K.E., M.H. Ralphs, J.A. Pfister, et.al. 2001. Plants Poisonous to Livestock in the Western 

States. USDA, Ag. Res. Serv., Agri. Info. Bull. No. 415. 107 pg.

ROW statistics

Highways – rural: https://www.fhwa.dot.gov/policyinformation/statistics/2014/hm220.cfm

Pipelines: http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national-

_transportation_statistics/html/table_01_10.html

Railroads: https://www.aar.org/Style%20Library/railroads_and_states/dist/data/pdf/-

State%20rankings.pdf

Electric: Federal Power Commission. 1976. Statistics of privately owned electric utilities in 

the U.S., 1974. Classes A and B companies.

Sheley, R. M. Manoukian, and G. Marks. 1999. pg 69-72. In: Sheley, R.L. and J.K Petroff (ed.). 

1999. Biology and Management of Noxious Rangeland Weeds. Oregon State University 

Press, Corvallis. 438 pg.

Sheley, R.L., J.K. Petroff, and M.M. Borman. 1998. Introduction. pg 1-3. In: Sheley, R.L. and J.K 

Petroff (ed.). 1999. Biology and Management of Noxious Rangeland Weeds. Oregon State 

University Press, Corvallis. 438 pg.

ACKNOWLEDGEMENTS

A number of people have contributed to the concepts and details included in this document.

Atkins, Lee, Progressive Solutions, L.L.C., Natchez, MS

Blase, Gerry. Asplundh Railroad Division, Ironton, OH

Earnest, Donnie, Enable Midstream Partners, Oklahoma City, OK

Ezell, Andy, Mississippi State University, Starkville, MS

Goodfellow, John, BioCompliance, Redmond, WA

Hecox, Doug, FHWA, Washington, DC

Johnstone, Rick, IVM Partners, Inc., Newark, DE

Kortum, Brian, NiSource Environmental, Merrillville, IN

Miller, Jim, Southern Forestry Experiment Station, Auburn, AL

Rumble, Jason, Ferrosafe, LLC, Glendale, AZ
35

CREDENTIALS

HARVEY A. HOLT, Ph.D.

Professor Emeritus, Purdue University

Address

Green Systems Analytics, LLC 765-427-5661 (voice)

10203 47th Avenue SW, B-9 holth@purdue.edu (email)

Seattle, WA 98146

Education

B.S. Oklahoma State University 1965 Forest Management

M.S. Oregon State University 1967 Forest Management

Ph.D. Oregon State University 1970 Forest Ecology

Work Experience

Green Systems Analytics, LLC January 2010 - Present

Manager

Consulting on herbicide product development and application.

Purdue University, Department of Forestry and Natural Resources January, 1975 - July, 2009

Associate Professor, Professor, and Professor Emeritus

Research activities focused on industrial vegetation management (electric, railroad, and highway rightsof-way, total vegetation control, and forestry), and trees in the urban environment. Research also 

encompassed tree growth retardants, pruning effects, planting treatments, herbicides, biopesticides, 

and application technology. Teaching included FNR 444 Arboricultural Practices and FNR 445 Urban 

Forestry Topics. The Midwest Urban Tree Care Forum, started in 2003, brought college students from 

surrounding states to Chicago for a weekend with the urban forestry profession. The extension program 

emphasized professional education for right-of-way managers, commercial pesticide applicators, 

commercial and municipal arborists, state and federal agency personnel, consulting and industrial 

foresters, and landowner and grower organizations. The Weed Control Seminar for the National Railroad 

Contractors Association was conducted annually for more than 30 years. 

University of Arkansas, Department of Horticulture and Forestry September, 1970 - December, 1974

Assistant Professor

Research emphasized forest vegetation management and evaluation of new application techniques. This 

included right-of-way brush control, weed control in pine and walnut plantations, tree injection, and 

chemical site preparation. Teaching responsibilities included Fundamentals of Forestry and Dendrology.

Citations in Biographical Works

American Men and Women in Science, 1972, 12th Edition
36

Professional Organizations - Memberships

International Society of Arboriculture

- Board of Directors, 1993 – 2008

- Executive Committee, 2001 - 2002

- Student Activities Committee, Chair, 2005 - 2008

Indiana Arborist Association

- ISA Chapter Representative, 1993 - 2008

Pacific Northwest Chapter, International Society of America

Arboriculture Research and Education Academy

Utility Arborist Association

Western Society of Weed Science

Weed Science Society of America

American Railway Engineers and Maintenance-of-Way Association

- Committee 1 (Track), Subcommittee 9 (Vegetation)

Council for Agricultural Science and Technology (CAST)

National Roadside Vegetation Management Association

Honorary Organizations

Alpha Zeta - National Agricultural Honorary

Epsilon Sigma Phi – National Extension Honorary

Gamma Sigma Delta - National Agricultural Honorary

Phi Kappa Phi - National Scholastic Honorary

Sigma Xi - National Honorary for Scientists

Xi Sigma Pi - National Forestry Honorary

Special Recognitions

1978-1979 – Chairman, Walnut Council

1979 – Chairman, Indiana Chapter, Society of American Foresters

1981 – Program Chairman, Walnut Council Annual Conference

1987 - Outstanding Paper Award, Weed Science

1991 – Distinguished Service Award, National Roadside Vegetation Management Association 

1992 – Silver Member Certificate, Indiana Society of American Foresters

1996 - Outstanding Teacher, Department of Forestry and Natural Resources, Purdue University

1997 - Meritorious Service Award, Indiana Arborist Association

1998 - Excellence in Roadside Management – Roadside Support Category, National Roadside Vegetation 

Management Association

2002 - Education Award, Utility Arborist Association

2004 - Outstanding Counselor, Department of Forestry and Natural Resources, Purdue University

2005 - Special Recognition Award, Illinois Arborist Association

2005 - Award for Excellence in Arboricultural Education, International Society of Arboriculture

2006 - Distinguished Service Award, Indiana Arborist Association

2006 - Adjunct Research Professor, Changbai Mountain Academy of Science, Jilin Province, China

2008 – Richard Harris Authorship Award, International Society of Arboriculture

2009 - Honorary Life Member, Indiana Arborist Association