Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 1 

Appendix I - Cumulative Effects Project List

Forest Service Activities

Almost all activities that have occurred, are occurring, or will occur on the Tonto National Forest

have or could potentially impact populations of invasive weeds either by introducing seeds or 

portions of weeds into non-infested areas, creating conditions favorable for the germination or 

spread, or by reducing native plants that serve to compete with weeds. This is a best attempt effort 

at describing the types of projects that have either occurred, are occurring, or will likely occur in 

the reasonable future and describes how the project could impact weed populations in the vicinity 

of the project. 

In addition, a list of projects that are currently being planned on the Tonto National Forest is 

included to serve as a representative sample for a typical schedule of proposed actions for the 

Forest. In parentheses behind the project name, the number references the discussion that best 

describes the project and the potential impact the project will have on weed populations. 

1. Roads and Rights-of-Way Management

This category includes road construction, reconstruction and road maintenance. The work is 

usually accomplished with heavy equipment including bulldozers, road maintainers, tractors, and 

crawler equipment. With annual mowing and maintenance of ditches and culverts, the work 

involves activity along many miles of roads through the National Forest. Generally, roadside 

mowing does not include extensive ground disturbance. Ditch reshaping and culvert replacement 

does create some disturbed ground in the vicinity of the project. All of these projects could bring 

weed seed onto the forests, or transport seed from existing infestations to non-infested areas. 

Where the soil is disturbed, such as during reconstruction or construction activities, the relocated 

or existing weed seeds have an excellent seedbed. Germination conditions within the ditches and 

along the roadways are generally good to excellent with adequate light and moisture provided. 

Current contract clauses for road management direct operators to clean their equipment before 

they leave one forest’s jobsite to go to another forest’s jobsite. The Tonto National Forest works 

with road management agencies and their contractors to control weed infestations prior to any 

new construction or heavy maintenance. 

Other rights-of-way such as utility lines, pipelines, telephone lines, and railroad tracks are 

developed and maintained including various types of treatments to control weeds and other 

vegetation. While most National Forest sections receive mechanical treatments, unknown 

quantities of herbicides are being utilized on some private sections of the rights-of-way. New 

construction and maintenance of these rights-of-way could introduce weeds due to the heavy 

equipment used and creation of good germination sites for deposited seeds.

2. Vegetation Management 

This category includes both green tree and salvage sales on the Forest, from within the wildlandurban interface to the far reaches of the Forest. A salvage sale occurs where a catastrophic event 

such as a wildfire or an expanse of trees have been killed by insects, disease or other 

phenomenon. A green tree sale is where forest managers have determined that there are excess 

trees and that some of these excess trees can be removed. The trees to be removed have 

commercial value and have been sold to an interested party. Harvest and removal of the trees 

generally involves the use of heavy equipment such as yarders, tractors, skidders, loaders, and 

logging trucks. The trees are felled, then moved either singly or in groups to a landing where they 
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2 Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

are loaded onto a truck to be removed from the forest. Timber sales generally necessitate a 

developed and maintained road system whose impacts have been previously analyzed. The 

logging operation provides a vector of infestation by either bringing weed seed into the logging 

unit, or distributing the seeds around the logging unit. With heavy equipment movement, ground 

disturbance occurs and provides a good seedbed for weed seed germination. With the harvest of 

trees, reduced competition for light and water exists for newly germinated weeds or the newly 

deposited weed seeds. With less competition and adequate nutrients and moisture, logging areas 

frequently have infestations of weeds. 

The harvest of firewood and Christmas trees are smaller versions of a timber sale. While these 

situations have less impact than a larger timber sale, the potential for an individual to transport 

weed seeds from further away and deposit them on the Forest is greater, since there are fewer 

mitigation measures in place that require cleaning of the vehicles prior to entering the National 

Forest. 

Areas where salvage sales occur generally have reduced local vegetative competition for weeds. 

In the case of a wildfire, additional nutrients and reduced seed sources for native vegetation exist. 

With mineral soils exposed over a large area, wildfire areas may be opened to large infestations of 

weeds. While part of this is due to excellent seedbed preparation, how wildfires have traditionally 

been fought on the national forests creates an ideal vector of infestation for weed seed. This issue 

is further discussed under “Fire Management.” 

Contract clauses for larger timber sales typically require contractors to bring clean equipment 

onto the Forest, and timber sale administrators usually inspect the equipment to ensure that 

compliance with this clause is obtained. With smaller sales such as for Christmas trees or 

firewood, there is less opportunity for inspection of vehicles before they go to the forest. 

Noncommercial or Precommercial Thinning – These activities include work to improve a 

resource area, such as a wildlife habitat improvement project or a timber stand by noncommercial 

or pre-commercial thinning operations. While some of the work is done with hand tools, some 

heavy equipment may also be utilized. Potential impacts from cultural treatment activities are 

similar to those from timber sales and road maintenance. If the work is accomplished using hand

tools, the impacts are comparable to firewood or Christmas tree sales. There is some additional 

possibility for contract administration to monitor and limit weed seed introduction, especially if 

the project is in a non-infested area and the contractor is known to be from an area infested with a 

specific weed. Due to the contractor covering essentially 100 percent of a project area, the 

chances that they will come in contact with existing weed populations and spread portions of 

those plants to non-infested areas does exist. In addition, when the contractor moves from one 

project area to another within the Forest, there is only a limited chance that the contractor’s 

equipment will receive a spray wash, unless the contract administrator is aware that the 

equipment is contaminated with weed seed and the area to be worked next is not infested. 

Whether or not the contractor stays on the site during the work activity or camps at another 

location conveniently located could impact the potential for weed seed dispersal either around the 

project site from the camping area or depositing weed seeds collected at the worksite in and 

around the camping area.
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Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 3 

3. Range Management 

Cattle and other livestock have the potential to pick up and transport weed seeds around the 

Forest and to carry seeds onto the Forest. Many grass and weed species’ seeds germinate better 

after they have traveled through the digestive system of an animal. Some seeds get stuck in 

animals’ coats, and in their hooves, tails, manes, or wool. In moving animals from pasture to 

pasture or along a designated driveway, the animals can distribute weed seeds from an infested 

area to a non-infested area. In the event that supplemental feed is provided for animals, unless it 

is certified as “weed free,” it can bring in new weeds to the Forest. To combat this potential 

vector of infestation, livestock are sometimes quarantined for a few days after they have been 

moved to clear their systems of weed seeds. 

Range permittees frequently drive through pastures looking at their livestock and have the 

potential to pick up weed and distribute them in non-infested areas. Fortunately, most permittees 

are familiar with the various species of weeds and take care to avoid driving through infested 

areas. Range improvement projects such as fencing, water tank development, or maintenance can 

create suitable seedbeds for seeds or disperse seeds.

4. Fire Management 

4a. Wildfires – Typically, firefighters from within the region drive to ongoing wildfires. They 

bring their equipment and tools and any collected weed seed with them. While most incident 

management teams coordinate high pressure washing of equipment before fire crews leave to 

return home, they do not always require all fire equipment to be spray washed and cleaned

before it goes to the fire line. On the Tonto NF, engines and other equipment coming in from 

off-forest pose a very real avenue for introduction of new species of invasive plants. 

In addition to agency equipment and personnel, most fires have a plethora of contracted 

equipment including engines, dozers, tractors and chippers. While most of this equipment 

gets a pre-inspection prior to going to the fire line, this may not include a spray wash to rid 

the equipment of any weed seed it might have picked up on its last job. At least some weeds 

are introduced to fire areas by this vector of infestation. The Tonto NF is working to educate 

fire teams to order contract equipment clean when it checks in to a fire incident.

Fire—whether it is a wildfire or a prescribed fire—creates conditions that are conducive to 

weed spread and maximizes their germination. Fires create an optimum seedbed, removing 

some competing vegetation and providing useable nutrients. This occurs during all stages of 

the fire through the rehabilitation process where fire lines are water barred, seeded, and 

mulched. In at least one case, weed infestations have been created by the use of contaminated 

seed mixtures. 

4b. Prescribed Fire – Prescribed fire has many similarities to wildfire in the creation of 

optimum conditions for weed seed germination and making nutrients available for the growth 

and development of weed species. In the timber vegetation types, prescribed fires do not 

eliminate the overstory vegetation from the burn area. Generally, prescribed fire operations 

do not bring in as many resources to the fire area as do wildfires. Using local resources who 

are familiar with local conditions and what portions of the forest or ranger district are weed 

infested by which species and which are non-infested minimizes the potential for new 

infestations to occur.
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4 Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Firefighters and personnel conducting prescribed burns can be vectors of infestation, if they 

have been working in weed infestations during their project work. They can spread seeds 

around the project area, bring seed to the project area from their home districts, or they can 

gather seed at the fire location and take seeds back home with them. The seeds can be in their 

clothing or on the equipment that they bring to a fire. 

5. Recreation Management and Activities

5a. Thousands of people come to the Tonto National Forest each year to recreate and enjoy 

the natural resources. Public use of Arizona national forests is probably slightly higher than 

the national average due to the climate. The mild Arizona winters make the Tonto National 

Forest attractive to residents and tourists alike. The Tonto NF provides an array of recreation 

opportunities year-round. Visitors to the Tonto NF retreat to the 29,000 acres of lakes in the 

desert, including Roosevelt, Apache, Canyon, and Saguaro lakes on the Salt River; Bartlett 

and Horseshoe reservoirs on the Verde River, the State’s only Wild and Scenic River. The 

Lower Salt River is one of the most popular “tubing” rivers in the nation. Many visitors can 

be found enjoying the cool pine forest under the Mogollon Rim from April to October, while 

hunting for big game including deer, elk, mountain lion, and black bear. The Forest is home 

to many miles of multi-use trails. The Tonto NF manages eight wilderness areas totaling over 

590,000 acres. They are administered to ensure public enjoyment, while protecting the unique 

natural character of these special places. 

While the local population visits the Forest, there is a continuous stream of out-of-state and 

out-of-country visitors, too. All forms of recreation have the potential to either introduce 

weed species to the Forest, or for forest visitors to collect weed seeds on the Forest and 

introduce them back at their homes or where they visit next. While the Tonto National Forest 

is a destination for vacations, many more people pass through the area on their way to or 

from another destination. 

Campers, hikers, motorcyclists, hunters, and others all have the potential to either introduce 

weeds into this area from where they have been with seeds being transported here in their 

equipment, or to take seeds from here and infest other areas. Some forms of recreational use 

have greater potential than others.

Equestrian use of National Forests is increasing. Horses are used for recreational riding, 

equestrian events, hunting, and during range management and other resource management 

activities. For people traveling cross-county with horses, the National Forests provide a 

location where they can allow their horses to relax after an extended trip, stretch their legs, 

exercise and graze outside the confines of a horse trailer. Combining camping and horse 

riding over large expanses of the Forest is popular. Viewing the Forest from the back of a 

horse and being able to get further away from the crowds is appealing to many equestrians. 

Groups of equestrians frequently ride together to visit historically used areas and explore new 

ones. Hunters frequently use horses to get to the back country in pursuit of game species and 

to bring the game that they have taken back to vehicular-accessible locations. Outfitter-guide 

operations use horses and other animals such as llamas to ride and carry equipment into the 

back country. The Forest Service and other land management agencies frequently use horses 

to check grazing improvements, such as fences or water improvements. Other types of 

resource management activities use horses, where they provide the most convenient or 

desirable transportation mode. 
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Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 5 

Horses, llamas, and other livestock all have the potential to bring weed seeds into the Forest 

or to transport weed seeds to a non-infested area. Seed transportation can occur as part of the 

animal’s feed and digestive process or can be carried on their exterior on their coats, manes, 

tails, or hooves. With events such as equestrian trail rides, endurance races or just gathering 

of acquaintances that occur on the Forest, it is common to see horse trailers, trucks, horses, 

and enthusiasts from multiple states camped in the forests for multiple days. In these 

situations, it is quite possible to transfer weed seed from several states away into the Tonto 

National Forest and then onto other states. While a period of quarantine would reduce the 

potential of spreading weed seed, there is not currently any policy requiring it in Arizona. 

Hay and straw for feed and bedding also can contain weed seed. Forest Service manuals 

direct that Forests comply with any state weed-free hay and feed programs. A Regional 

Closure Order is planned to bring all National Forests in New Mexico and Arizona into 

compliance with the manual and new weed-free hay, feed and mulch state programs.

Arizona’s Weed-Free program was initiated in 2004 (ACIA, 2005). 

There are numerous activities involving the management or development of recreation 

facilities that have potential impacts to weed infestations. Construction of buildings and 

facilities is discussed below in “7. Lands and Mineral Resources, Administrative or Special 

Use Area Development.” 

Trail construction and maintenance activities involve work using hand tools and sometimes 

bigger equipment. Ground disturbances created by this equipment can create sites conducive 

for weed seed germination and development. Movement of this equipment from an infested 

area to a non-infested area can disperse weed seeds and expand the area of infestation.

5b. Off-Highway Vehicles (OHVs) – Off-highway vehicles, including jeeps, trucks, dune 

buggies, all terrain vehicles (ATVs), and trail motorcycles, are used extensively along roads 

and trails throughout the Tonto NF. Some cross-country travel occurs with all vehicles, but 

ATVs and trail motorcycles make up most of this impact. Some specific uses of these 

vehicles are discussed in separate sections where the potential impacts to noxious weeds vary. 

These vehicles provide the public with a less strenuous and, in many cases, a faster way to 

see the back country. People can explore canyons and mountainsides, with the push of an 

accelerator pedal or thumb switch. Places where only the hardiest hikers could reach after 

several days of strenuous hiking can now be reached in a few hours of riding. The use of 

OHVs on National Forests has increased over the last 10 years and is likely to continue 

increasing in future years. New ATVs are bigger, more powerful, and are going places that 

few imagined possible in the past. Other OHVs are following the same route as ATVs, but at 

a slightly slower rate although there are areas where concentrated OHV use and enthusiasts 

equal or exceed ATV use. 

OHVs serve as vectors of infestation in that they carry weed seeds from infestations to areas 

of non-infestation. There currently are no requirements for operators to keep their vehicles 

clean of mud, dirt, and weed seed. While vanity and owner pride of showing off a shiny and 

technologically enhanced vehicle keep some vehicles free of mud and weed seed, an equal 

number of operators use their dirt (and possibly weed seed) covered vehicles as proof that 

they have “been there and done that.” OHVs can also disturb sufficient soil to prepare 

seedbeds for weed seeds. In areas of concentrated use, vegetation and ground cover is either 

heavily disturbed or eliminated.
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6 Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

In 2003, Forest Service Chief Dale Bosworth acknowledged OHVs as one of the four main 

management issues facing the Forest Service. By the year 2000, there were almost 36 million 

OHVs in the United States. In July 2004, the Forest Service drafted a National OHV policy 

that proposed a national framework to guide local designation of roads, trails, and areas for 

OHV use and prohibit cross-country travel. While this policy does not limit the number of 

OHVs on the Forest, it will limit where they can travel in the future. This policy will serve to 

reduce the areas that are infested from this vector to along road and trail borders. 

Forests in Arizona are either working on or have completed travel management planning. The 

Tonto National Forest has received comments on its draft environmental assessment for travel 

management and will be completing the analysis, with a decision anticipated in the next year.

The purpose and need of that document are to stop the impacts of travel between roads and 

trails by OHVs on areas currently open to their use. National Forest land and resource 

management plan amendments for the Tonto National Forest will be developed in conjunction 

with the environmental assessment. The decision for this document, when signed and 

implemented, will further reduce the potential for OHVs to be vectors of infestation of weed 

species both on National Forest and private land. 

OHVs and, in particular, ATVs are used extensively during the big game hunting season. 

ATVs facilitate scouting efforts and transport hunters around the forests with less wear and 

tear on their bigger OHVs. During the season, hunters can get to the back country quicker and 

generally with less effort. If they are successful, they can get their harvested animals back 

out. Moving several hundred pounds of elk quarters with an ATV or easing a 4 x 4 truck near 

the site of a harvested animal is much easier than hauling those same elk quarters out of the 

back country in a backpack, one at a time. While there are roads and trails that hunters use, 

there is also a lot of cross-country travel that can cause or expand weed infestations by 

spreading weed seeds or parts of weed plants into non-infested areas. While some of the 

cross-country OHV travel will be reduced in conjunction with travel management planning 

discussed above, at least some of the use described here will continue. 

5c. Hiking – Hikers probably carry a few weed seeds into non-infested areas in their clothing 

and equipment. It is doubtful that they are responsible for many new infestations, although it 

is likely that they expand some infestations by picking up weed seeds in their boots or 

clothing and depositing them into non-infested areas. 

5d. Mountain Biking – Mountain bikes are an alternative non-motorized method of seeing 

the back country. While many bikers are looking for established trails or old roads, some are 

content rolling along a game trail or going cross country. Mountain bikes are used by some 

recreationists to get further away from the crowds. In comparison to OHVs and hikers, 

mountain bikes probably distribute fewer weed seeds than ATVs or OHVs, but slightly more 

than hikers. This assumption is based upon the differences in the average distances traveled in 

a day’s time.

5e. Outfitter Guide Operations – These operations vary in type and nature, but in general 

are trips into the forest that the public pays to participate in. Guides provide a variety of 

services including, but not limited to, transportation, meals, drinks, and equipment such as 

rafts, tents, horses, ATVs, and OHVs. The guides generally know the forest area that they are 

presenting to the public, but not always. Generally, outfitter guide groups can disperse weeds 

and weed seeds into non-infested areas with their activities. The amount and degree of this 
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Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 7 

would be comparable to the discussion presented above for comparable types of 

transportation being used. It is likely that some guides recognize some of the weed species 

and know to avoid them. This would have a net reduction of impact from this vector. 

Some outfitter guides provide tours of the forest along main roads or scenic routes. While 

these may get off the paved highways, it is doubtful that they contribute much to weed seed 

dispersal. It is likely that at an overlook or parking lot some weed seeds could be picked up 

and then dropped off at another stop. 

Some outfitter guides may provide a camping opportunity to the public. In these situations, 

the group travels through the forest to a designated camping area. They may travel in 4 x 4 

vehicles, ATVs, horses, bikes or hike through the forest to the designated camping area. 

These camping areas are generally large enough to support larger groups. Over time, the 

numbers of people using these locations increase above and beyond the outfitters and their 

clients to include private parties that find the area desirable for camping purposes. Through 

the increased use, native vegetation is reduced and the area becomes conducive for 

germination of weed seeds. These seeds can be brought in on equipment, with horses either 

on tack, in feed, or in their digestive systems, or on other modes of travel. Since the area is 

being used on a somewhat regular basis, the potential exists for more seeds or parts of the 

weed plants to be picked up again and transported to another non-infested area.

5f. Developed Recreation – Established recreation areas have more concentrated public 

usage than do dispersed recreation sites and, as a result, they have greater potential for having 

weeds introduced, harboring weeds and serving as a source for weed seeds. There is a greater 

potential that weeds from more distant places are introduced at developed sites as people

from across the country use the areas on their way to and from distant destinations. It is not 

uncommon for cross-country travelers to leisurely travel 300 or more miles in a day and still 

have time to stop and see local sites and attractions. Frequent stops and camping early 

provides the necessary timing for either picking up weed seeds or depositing them in the 

campground. 

When using developed recreation areas, the public uses a variety of equipment from selfcontained, fully powered recreation vehicles (RVs) to lightweight, back-packing equipment. 

During periods of nonuse, RVs are frequently parked in a location where weed populations 

exist. Over time, the weeds may grow into or become attached to the RV. When the RV is 

mobilized for a trip, these weeds may or may not be cleaned from the RV before departure. If 

the weed seeds are picked up at the recreation site, they are carried home and likely deposited 

where the RV is stored, perpetuating this cycle. 

Tents and smaller pieces of camping equipment can and do serve as a vector for transporting 

weed seeds. There is more discussion about this above.

5g. Special Use Permitted Events – Throughout the year, there are numerous events of 

various types that can serve to further spread the seeds or parts of weed plants. These 

generally are more organized and attract people from further away. Examples include, but are 

not limited to: American Cancer Society Walk for a Cure, sporting events such as muzzle 

loader or archery competitions, marathons, trail rides, mountain man rendezvous, organized 

group events, organized auto and motorcycle tours, and family reunions. These events are 

frequently combined with using RVs, and camping, and can either spread weeds onto the 
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8 Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

forest or take weeds back to non-infested private lands. These events have similar potentials 

for weed dispersal as their principle mode of transportation described above has. In the event 

that a group brings multiple types of recreational equipment such as OHVs and horses, the 

event may serve to both distribute weed seeds on the forest and collect other species of weed 

seeds and distribute them in a non-infested area.

6. Stewardship Resources

While many human-caused types of weed seed dispersal have been discussed, another source of 

weed spread is wildlife. Some weed seeds are edible by wildlife and are carried from an area of 

infestation to an area where they are deposited. Wildlife can also carry weed seeds in their coats, 

feathers, or on their hooves.

7. Lands and Mineral Resources

7a. Administrative or Special Use Area Development – Throughout the Forest, there are 

periodic projects to build new facilities or repair and renovate old ones. This work generally 

removes vegetation, disturbs the soils, and creates areas more conducive to seed germination. 

The movement of heavy equipment from off-forest can introduce new weed species or seeds. 

Projects that fall into this category include construction projects in existing or new sites, 

ranging from building a communications tower to a new district office. Within many existing 

recreation sites the renovation of existing facilities or the addition of new ones is occurring. 

These activities can create suitable germination areas for weed seeds and can also serve as a 

vector to move seeds from infested areas to non-infested areas.

7b. Minerals/Mining Management – The Tonto National Forest has a rich history of 

producing copper, gold, silver, mercury, uranium, asbestos, tungsten, iron, and many other 

associated metals. This history spans over 150 years and consists of 38 mineral districts with 

recorded mineral production. There are currently many small mining operations throughout 

the Forest and several large operations within the Globe-Miami Mining District location of 

regional disseminated and porphyry-type mineral deposits. The legacy of mining activity has 

also generated numerous abandoned mine lands. The Forest is currently reclaiming these 

areas and securing physical safety hazards. 

Several active sand and gravel type operations, which are operated by the Arizona 

Department of Transportation and local Counties for the purpose of road maintenance, are 

located across the Forest. 

The operation of all these active sites, and the reclamation of abandoned mine sites involves 

some use of heavy equipment. The disturbance creates sites conducive for seed germination.

Movement of equipment from one site to another can serve as a vector for weed seeds or 

plants.

Off-forest Activities

8. Rights-of Way Development and Treatments

Each year highway departments at the local, county, State, and Federal levels do some roadside 

herbicidal treatment of weeds. While the majority of this occurs on private inholdings within the 

forests, some Federal easements on the National Forest are also treated. In May 2004, Forest 
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Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest 9 

Supervisor Karl P. Siderits signed a decision authorizing herbicidal treatments along 

approximately 2,700 miles of interstate highways, U.S. highways, and State routes within the 

boundaries of the six National Forests in Arizona. This effort would treat approximately 1,000 

acres per year on the Tonto National Forest. This work will be completed on Forest Road 512, 

and State Highways 177, 277, 87, 260, 60, 188, 288, and 88 (USDA, 2004, May).

There are some herbicides applied to the roadsides by local counties and city governments, the 

exact amount and types applied is unknown. Rights-of-way such as utility lines, pipelines, 

telephone lines, and along the railroad tracks are developed and maintained including receiving 

various types of treatments to control weeds and other vegetation. Unknown quantities of 

herbicides are being utilized on some private sections of the rights-of-way. Construction of these 

rights-of-way could introduce weeds, due to the heavy equipment used and creation of good 

germination sites for deposited seeds.

9. Other Pesticide Use

Throughout the last few years, there have been other projects proposed or accomplished that have 

used pesticides. These projects include incidental use of insecticides and rodenticides, and minor 

“housekeeping” use of herbicides. None of these treatments would have any impact on weed 

populations, unless the equipment used or the operator carried seeds into the project area or 

moved seeds around the project area from an existing infestation.

Historically there have been some herbicides applied around administrative sites and recreation 

areas on private lands scattered across the project area. Additional efforts to control the spread of 

weeds occur when weed management areas are established. Regions within the project area that 

now have (or are developing) weed management areas (WMAs) include the Tonto Weed 

Management Area (follows the same boundaries as the Tonto NRCD) and the Central Arizona 

Weed Management Area. Though weed management areas may focus more on information 

gathering and educational aspects, they often complete small ground treatments. Typically, the 

integrated weed treatment methods used are manual and cultural, although WMA partners have 

used herbicides on non-forest lands.

The State Land Department in the New River area (adjacent to the Cave Creek Ranger District)

has begun a program of Malta starthistle treatment using Department of Corrections crews to 

hand pull and also using treatments with the herbicide Milestone (aminopyralid). This infestation 

is on state, private, and National Forest land, and the Tonto NF plans to join them in this effort.

Assessing herbicide use within and adjacent to the project area is difficult, since there are so 

many herbicides where there are no requirements for the seller or purchaser to contact the State 

and inform them of the product’s use. The State notes that the only products it has control over, 

and requires reports, are those herbicides that are considered restricted use (Arizona Department 

of Agriculture, 2005). There may be quite a bit of restricted herbicide use in central Arizona urban 

areas, golf courses, and agricultural fields and orchards. 

Statistics are readily available on the kinds and amounts of herbicides used on agricultural lands 

in Arizona. Most of this use is occurring in Yuma and Maricopa counties, where large irrigation 

districts have been formed. Large amounts of herbicides are typically used in agricultural lands in 

Maricopa County. This land use is diminishing, as the population in the greater Phoenix area 

grows and housing developments are constructed where orchards and crop fields once were.
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10 Environmental Assessment for Integrated Treatment of Exotic Invasive Plants on the Tonto National Forest

Some of the most popular herbicides used for turf and landscaping include clopyralid, 2,4-D, 

dicamba, and glyphosate. 

Golf courses require extensive use of pesticides for upkeep and maintenance. Extensive use of 

herbicides is required to maintain greens, fairways, and the roughs. Their efforts to maintain the 

necessary vegetation includes treatment of weed populations. There are over 200 golf courses in 

watershed in the area of the Tonto National Forest. See cumulative effects discussion under 

Human Health for information on quantities of herbicides used in these areas, and also for an 

estimate of herbicides used by households. 

Both Spur Cross County Park and Desert Foothills Land Trust utilize herbicides to reduce 

noxious weed infestations on lands they manage in the vicinity of the Cave Creek Ranger District.

They both conduct saltcedar removal projects using the cut-stump method and application of 

Garlon-4.