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Suppressing weeds in the quarry environment

By |  May 1, 2017

Weed management doesn’t top the task list for most quarry managers. However, keeping noxious weeds at bay is becoming more critical as invasive weed battles continue to intensify across the United States.

Suppressing weed growth and reducing the spread of weed seed to other sites through materials or equipment are two key ways managers can effectively deal with weeds at a quarry site.

“A review of cost benefit analysis of controlling various non-native invasive species suggests that it’s 17 times cheaper to implement prevention practices than to apply management once they are established,” says Corey Ransom, associate professor of weed science, Utah State University (USU). “Once weeds become established in an area, you have to spend money to treat them every year.”

Traveling weeds

Because transportation in and out of a quarry is a key element of the business, products produced in one area may be carried or shipped long distances, even to other countries. The result can be what the authors of “Fortifying Farms and Ranches Against Weed Invasion” call “long-distance weed dispersal.”

“That means new weeds are showing up in areas where they didn’t appear before,” Ransom says. “The problem with that is those weeds are often more aggressive, persistent, harmful and more difficult to control than the weeds historically managed in a specific area. With changing climate conditions, we also have concerns that weeds that didn’t thrive in average moisture conditions could pose a serious problem if we see more frequent dry weather cycles.”

Preventing both the arrival and spread of weeds is an important step in keeping invasive weeds at bay at any location. If aggressive weed species aren’t managed when they’re present in small areas, they can easily become unmanageable once they invade thousands of acres.

“Weeds don’t recognize boundary lines,” Ransom says. “Material from quarries that’s transported a significant distance could easily bring new, noxious weed species to an area.”

Growing conditions

Early and thorough herbicide treatment is the most effective management tool for suppressing invasive weeds. Photos courtesy of weedimages.org.

Disturbed soil encourages weed growth and expansion. It’s also a primary element at rock quarries. Construction sites where quarried material is often deposited – whether a bridge, building or road – also feature disturbed soil.

“A clear example of how important it is to do all we can to prevent spreading weeds this way is a trip I made with colleagues a few years ago to map invasive weed species in Big Cottonwood Canyon near Salt Lake City,” Ransom says.

“As we searched for a trailhead that was located in a summer home area, we came across a new bridge where fill material was recently placed. We saw a new species of weed there that had not been observed at that elevation in the canyon before.”

Keeping weeds under control

Weed management can be accomplished either in a proactive or reactive way. In a reactive system, weeds are usually well established before treatment is implemented. Because of the aggressive and persistent nature of noxious weeds, once established, they are likely to become a permanent feature of the landscape.

Proactive weed management involves education that aids in identifying weeds as well as effective management practices to suppress their growth. The most effective plan includes steps to prevent arrival of new species, establishment of existing or new species and management designed to prevent the spread of existing species.

“If new weeds do appear, treating them right away is key to preventing them from becoming established,” Ransom says. “If they become a persistent problem, the next-best defense is to prevent them from spreading any further.”

Weed seeds travel by water, wind, on animals and through human contact and interaction. Weed seeds caught in shoes, on clothing or hidden in materials transported from one place to another have potential to germinate and grow in new areas. Some weeds are adapted to travel most easily in one of these ways.

In order to suppress weeds from being transported via water, monitor bank and ditch areas late in the growing season when weed seed production peaks. Screening water before it’s transported to a new area can help remove weed seeds.

Extreme weather – like hurricanes, tornadoes and thunderstorms – can carry windborne seeds long distances. Scouting a quarry for emergence of new weeds following this type of event can help reduce the establishment of new weeds. Removing or burning existing weeds along fences, windbreaks, in gullies, canals and ditches can reduce the area’s weed-seed reservoir.

“Utah has been the epicenter for some noxious weeds that were introduced decades ago and now are so widespread there aren’t enough resources to help manage them,” Ransom says. “It was introduced here by early settlers. At that time, no one had any idea of its potential to spread and become a noxious weed.”

Dyer’s Woad was originally grown in Europe for the blue indigo dye extracted from its leaves. During the Middle Ages, it was a huge trade item. As the Asian Indigo plant emerged in the market, Dyer’s Woad’s importance faded. During the past century, the plant’s aggressive growth traits led it to become known as one of Utah’s noxious weeds.

Setting gravel standards

Photo courtesy of weedimages.org

Invasive species, such as Russian olive seen here, can quickly overtake native grass species in areas where soil is disturbed by mining activities.

Demand for weed-free gravel has led the North American Invasive Species Management Association (NAISMA) to develop Weed Free Gravel Pit Inspection standards and to provide a downloadable gravel pit inspection form on its website (naisma.org).

Current standards include the requirement that gravel or borrow material be inspected in the state/province of origin by the proper officials or authority and that gravel or borrow materials be inspected in the area of origin.

“We are working to provide a standard that will bring consistency in weed management protocols across the nation,” says Marsha Watland, NAISMA board of directors member and Minnesota’s Becker County ag inspector. “NAISMA members believe it’s important to maintain consistency in weed management programs to keep our land as weed free as possible. One main objective is to reduce propagation of weed seed and the spread of plant parts, which typically results in loss of pasture land and public natural resource.”

As a NAISMA board member, Watland is working with the NAISMA Weed Free Forage Committee, which consists of 17 states, to develop a gravel pit certification program that can serve as a model across the United States. Providing that standard will aid quarry owners in reducing movement of invasive and noxious weeds both in the United States and Canada. The protocol is being developed to include not just the quarry site but also the surrounding area where trucks travel in and out, potentially carrying invasive plants and seeds along their transport routes.

“Our role in gravel pit certification will be one of education and promotion of the certification practices,” Watland says. “We are planning an October 2017 meeting in Reno where our 30-member committee will gather to share input on the certification process and requirements. We want to cover all aspects of an effective certification standard to accomplish our goal of establishing consistent protocol.”

Watland’s background in county weed management helps her understand the challenges local weed management entities face. Because counties often deal with as many as 80 weed species in their localized area, NAISMA is limiting the developing weed protocol to encompass the most invasive weeds typically found in the United States.

NAISMA’s weed-free gravel pit certification is likely to include a third-party, certified weed specialist, spring and fall “walk through” with quarry owners to identify weed issues at a quarry site and aid in development of a treatment plan. Minimum NAISMA inspection guidelines involve walking or driving around the entire border of the gravel or borrow pit and inspection of all storage areas and gravel or sand piles. Areas around equipment, crushers and working areas are to be inspected at least twice each year during the growing season.

Treatment approaches in the final certification standard will include a pre-emergence and post-emergence plan. Quarries that have already implemented a plan have seen a positive response from customers and their community.

“A weed-free program could increase the value of gravel pit products,” Watland says. “Some quarry owners have found that a segment of their customer base buys just weed-free products. We are working to foster cooperation between the nation’s federal, state, municipal and county, as well as private land managers, to help battle invasive weeds.”

Ransom notes implementing an effective weed management program requires coordination and planning related to how, when and where quarry products are used.

“At a new construction site, weed management can be challenging because you don’t want to use chemicals that damage desirable plants,” Ransom says. “We recommend consulting a weed specialist in your area or one in your company to help put a weed management plan together.”

In every industry, weed problems constantly change. Some longtime battles go through changes and emergence of new invasive species requires new research and education plans.

“Our main goal is to manage any new weeds at an early stage to make a big difference in their growth before they spread to thousands of acres,” Ransom says. “Because society is more mobile than ever, opportunities for weed distribution are also greater than ever.

“Managers should keep in mind that in some instances, they may be eligible for assistance with management of noxious weeds,” he adds. “Before implementing a chemical program, check with your county to learn about assistance with spraying costs.”


Loretta Sorensen is a freelance writer in Yankton, South Dakota. She produces material on a variety of topics, serves as a ghostwriter and has authored her own books.


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