Regulating Growth: PGRs

The largest turf area Lawnscape Systems has applied a plant growth regulator (PGR) on was Leisure Village, a retirement community in Camarillo, Calif.

The company used a turfgrass growth regulator on all 186 acres of the property for more than one year, according to Richard Wills, vice president of the Ontario, Calif.-based company.

"The product cut the turf’s growth rate in half for the entire year," Wills said. "We reduced their clipping yield and dump costs by almost 60 percent. We cut the wear and tear on their equipment – their gas, oil and maintenance dropped a little more than 50 percent – and they were able to reduce their water consumption by about 21 percent."

While all these numbers, Wills explained, were impressive on their own, the real savings were in manpower. "This PGR reduced the need for mowing crews by 26 weeks," Wills said. "Their entire mowing staff had an extra 26 weeks to spend on other maintenance improvements around the property."

The experiment was an overwhelming success, except for an odor issue that existed with the PGR he used, Wills said. "The product had an odor at that time and many people who lived in the retirement community found it offensive, so for a short period of time the applications were stopped until a solution could be found," he explained. "Now that new, odor-free products are on the market, there is a renewed interest in restarting the use of a turf growth regulator on the property."

Just as Wills’ experience proved, PGRs are considered management tools for landscape contractors because of their ability to reduce mowing and clippings and save contractors time and labor, according to Jim Davis, northern region manager, Aventis Environmental Science, Montvale, N.J.

"From the chemical standpoint, this is the fastest growing segment in the turf industry," Davis said. "In the last decade, the PGR market has grown four to five times in size from single digit millions to approximately $25 million."

As PGRs become more widespread in the landscape industry, lawn care company owners must understand the product’s purpose, learn about the different types of PGRs on the market and train their employees how to use PGRs properly in the landscape.

THE PURPOSE OF PGRs. Plant growth regulators impact the growth cycle of plants. "Generally, people think of growth retardant activity in connection with PGRs," pointed out Laylah VanBibber, advertising manager, PBI Gordon, Kansas City, Mo. "But there are also growth regulator products used in nursery and floral production that enhance the growth cycle of plants. In the landscape, PGRs are generally used to decrease plant growth, including turfgrass growth regulators that minimize mowing requirements, clippings or eliminate seed heads and ornamental growth regulators that reduce trimming labor or clean-up requirements, increase or decrease bloom or decrease fruit-set on shrubs, ground covers or trees."

There are several different types of PGRs, VanBibber explained, and a product’s mode of action varies based on the chemistry used to produce it. "Some PGRs are weaker versions of weed control products," VanBibber said. "The herbicidal activity has been lightened so that the plant is just stunted instead of killed. Other types of PGRs interfere with the growth and/or reproductive cycle of the plant. And some PGRs inhibit certain plant hormones, creating smaller, miniature plants."

PGR products that slow the growth of trees and shrubs have limited use in the residential landscape, said Dennis Shepard, research director, Novartis, Overland Park, Kan. "However, the key use of PGRs in the landscape is on turfgrass," he noted.

PGRs for turfgrass developed prior to the 1980s slow turf growth by slowing cell division, according to Shepard. "These products are taken up by the foliage and do a good job of inhibiting seed head production," Shepard said. "PGRs developed in the 1980s slow turf growth by slowing the production of gibberellic acid (GA), a plant hormone that aids cell elongation. These products are taken up by the roots and must be watered into the turf.

"Newer PGRs registered in the mid-1990s slow turf growth by slowing the production of GA1, the primary form of GA in plants that affects cell elongation, while allowing the other forms of plant GA to carry on with their respective plant processes," Shepard continued. "Other newer PGRs slow turf growth by enhancing ethylene production."

While PGRs affect plants’ growth cycles, their long-term use has not been detrimental to plant health, according to Rich Hanrahan, senior technical development manager for the Chipco professional products division of Aventis Environmental Science. "In fact, recent research indicates that the PGR use actually might improve plant vigor and health."

However, VanBibber said long-term effects on plants depend on the PGR and how it is used. "Some PGRs cannot be used in back-to-back applications," she explained. "Other PGRs actually benefit root growth as a result of redirecting energy normally used for top growth. Turfgrasses treated with another type of PGR experience a rebound effect when the growth regulation wears off during which the turf becomes intensely green and increases shoots growing from the base of the stem of the plant."

When applied at label rate, Shepard said the foliar growth of a PGR-treated plant slows approximately 50 percent for up to four weeks. During this time, the turf is still carrying on photosynthesis and other growth and development processes, while energy is redirected to lateral and below-ground stems and roots. Change promotes growth, so turf will become denser and more tolerant to wear when PGRs are used long term, Shepard pointed out. "The turf also becomes a darker green because chlorophyll is more concentrated," he said.

PGR USE IN LANDSCAPES. Lawn care operators are using PGRs in a few different ways. Wills applies regulators on a daily basis to many sites to prevent trees from fruiting and to slow down shrub growth. Not too long ago, this was the primary use for PGRs, Wills said.

Today, the most common use of PGRs is for turfgrass growth reduction to decrease mowing and clippings during peak growth seasons – April to June and September to October, VanBibber pointed out.

When used on turf, PGRs are beneficial to landscape contractors, Davis said, but this depends on the type of job the contractor does. "If contractors are getting paid by the number of times they mow, the last thing they want to do is use a PGR," he said. "Some contractors, however, have a contract to maintain a property and they will spend money on a PGR to make money saving time on one area of a property and taking care of another."

Scott Hall, president, Classic Landscape, Frederick, Md., gets paid to mow his clients’ properties every week, but he still uses a PGR to control turf.

"I am not interested in reducing our mowing; our clients pay to see us do the job every week," Hall said. "What interests me is reducing our mowing problems. Wet weather, excessive top growth and clipping problems, which often occur around May or September, can handicap the schedule and interfere with herbicide applications, bedding installations, pruning, trimming and other tasks."

Other contractors, who still may not sell PGR applications, use PGRs to decrease time spent on a job so they can expand services beyond mowing without having to hire additional employees, VanBibber remarked.

"A straight lawn care company might sell PGRs as ways to control costs, reduce manpower needs, save water or simply to enhance the appearance of properties," Wills added. "A landscape maintenance company may view PGR use as an internal cost that increases staff productivity, reduces dump fees and equipment costs and acts as a customer retention tool."

Most contractors do not charge clients for PGR applications.

"We may or may not mention the PGR to the client, but we don’t charge for it or reduce mowings," Hall said. "PGRs increase our efficiency in getting the job done right."

So for contractors who spend anywhere from $20 to $80 per acre on a PGR, depending on the type of product used, how are their costs warranted? Davis said seeing this cost justification might be easier for a full-service maintenance contractor than a contractor who strictly mows lawns. "If you’re spending $50 or $80 an acre and you are maintaining a residential facility on a contract, you may absorb the cost or put it in the contract," Davis said. "If maintaining the facility on the contract was $100,000 last year, that cost certainly won’t come under $100,000 this year. Using a PGR on the property will help you lower your costs. So, if you had $50,000 in labor costs, now it will be cut to $30,000 and you only spent $5,000 on the PGR. Contractors are using this product to save costs, and, therefore, make money."

COST CONCERNS. As Davis mentioned, $20 to $80 per acre is a wide cost range for PGRs. The reason for this considerable gap is that "older compounds might be 25 percent of the cost of newer compounds," he said. "But the residual might be to spray every week vs. four or five weeks. So, some products are more expensive, but those are the ones that tend to have a longer residual."

Because of the wide variety of products on the market, Davis said evaluating the length of control in relation to cost per thousand is important when lawn care operators are evaluating the cost of PGRs. "Don’t look at the cost per thousand alone, look at the cost per day of control," he said. "This will give you the true cost of the product. If you buy a cheaper product that has to be sprayed weekly, you are going to have to buy more of that product to do the same job as a newer product that only has to be sprayed every four weeks."

"Turfgrass PGRs have been a little expensive in the past," added Wills, who has used PGRs in one form or another for almost 15 years, "but costs are coming down."

This is why PGR history and product types are important for contractors to research, Davis said.

For example, early turfgrass regulators caused yellowing turf and made turf more susceptible to insect and disease problems, Wills said.

Older compounds typically stressed the plant by stunting its growth. "Older products thinned the plant," Davis explained. "These older products are fine on areas where aesthetics aren’t important, such as near airports and warehouses.

"Newer PGR products, however, combine growth reduction with stress conditioning to increase root growth and enhance the plant," Davis continued. "After all, most landscape contractors are getting paid to mow green grass."

ACCURATE APPLICATION. While roadsides and other low-maintenance turf areas can stand a higher application rate while sacrificing some aesthetics, residential turf cannot. "Some PGRs can be used to hold top growth for up to eight weeks at a high rate, but at this rate, the turf will have some discoloration," VanBibber said. "Some PGRs are very rate sensitive and the rate of product used affects the rate of growth control."

Tom Watchke, turfgrass science professor, The Pennsylvania State University, State College, Pa., recommended that iron be used with PGR applications to prevent discoloration.

"Landscape contractors have found it valuable to slow growth with lower rates during peak growth seasons to allow more flexibility in scheduling, especially during periods of heavy rain when mowing is not possible," VanBibber explained.

Also, the length of control varies based on what type of grass is being treated. Some PGRs work better with certain turf types, such as bluegrass or ryegrass. Other products might work better on a transition zone or warm-season grass like Bermudagrass. Contractors need to evaluate their needs and then choose a product that works the best to meet those needs, Davis said.

"Warm-season grasses require such high rates, which can make the product too expensive for broadcast treatments," VanBibber said. "As a result, many landscape contractors use the product primarily on perimeters and along curbs and sidewalks to avoid labor-intensive edging and trimming in both cool-season and warm-season grasses."

Landscape contractors need to remember that PGR applications inhibit plants’ ability to outgrow the effects of insect damage, disease and wear from traffic. So, other product applications might be worthwhile to use when applying PGRs.

"Turfgrass areas treated with PGRs, especially at higher rates, should be monitored closely for disease and insects," VanBibber commented. "Also, weeds, which are not controlled by turf PGRs, are a greater concern in PGR-treated turfgrass areas during the regulation period. An herbicide treatment is always recommended in conjunction with the use of PGR products."

Some manufacturers recommend that PGRs only be used on high-quality turf so contractors are paying for a product they can get the most benefit from without having to battle other concerns, such as poor turf or other disease and weed stresses. "PGRs are not magic bullets for turf," Shepard said. "They are landscape tools that should be used in conjunction with other cultural practices in lawn maintenance."