AUSTIN (KXAN) — In the year since the 2021 winter storm, many utility companies focused their efforts on keeping tree limbs off distribution lines to prevent power outages. However, there’s a growing number of utilities using chemical solutions to manage branches, instead of pruning and trimming trees.

Pedernales Electric Cooperative power lines run right over Tony Cassandra’s fence line, so he said he wasn’t surprised a crew came by to assess the surrounding trees. Cassandra told KXAN the crew left a door hanger explaining they would be applying a Tree Growth Regulator, or TGR, called Cambistat to the trees near the lines, in order to “reduce growth” and “increase health.”

However, he became concerned when he read the growth of surrounding grass, shrubs, flowers and other vegetation could be slowed as well.

“Even if I was OK with them stunting the growth of that one tree, am I OK with them stunting the growth of everything around it?” he said. “I don’t think so.”

A spokesperson for Pedernales Electric Cooperative said the product increases safety for its crews, promotes tree health, saves money for their cooperative members and strengthens reliability against outages.  

“These products are regulated by the Texas Department of Agriculture (TDA) and always applied by a TDA-trained and licensed contractor,” he said.

PEC said its “targeted” use of herbicide products is part of an overall strategy that also includes hand-cutting, mowing and mulching.

What are these products?

Daphne Richards, a horticulture expert and agent with the Texas A&M AgriLife Extension Service, said there are dozens of these kinds of products — also called tree growth inhibitors or tree growth retardants — that share the active ingredient Paclobutrazol.

She said it has been most commonly used on smaller plants, but more utility companies have been relying on it as “one tool in their management toolbox,” as they try to keep customers safe from outages or even dangerous wildfires caused by trees falling on power lines.

Here’s how it works: the chemical mimics a plant hormone by keeping the cells on the woody part of the plant between branches from elongating and stretching and by keeping the overall plant more compact.

A door hanger explaining the Tree Growth Regulator program for a Northwest Austin neighborhood (KXAN Photo/Avery Travis)
A door hanger explaining the Tree Growth Regulator program for a northwest Austin neighborhood (KXAN Photo/Avery Travis)

“The tree produces the same number of leaves, the same number of branches. It just causes them to stay closer together,” she said.

Richards noted there are several benefits to using these products over pruning.

For instance, TGRs can help maintain the look and shape of a tree, while avoiding damage to the tree’s health caused by pruning at the wrong time of the year.

“[The utility company] can’t prune every tree in our neighborhood — in our community — all in the window of time when maybe trees need to be pruned and when it’s most beneficial for that tree to be pruned,” she said. “Let’s use oaks as an example. There’s a couple of really short windows that we recommend oak trees being pruned.”

Several studies also show TGRs cause leaves to have a more rich, green color and also protect against fungal diseases that can attack urban trees.

Still, the labels for these products feature some specific warnings and restrictions — as well as a “caution” notice.

According to Environmental Protection Agency documents, caution is the lowest toxicity category that can be found on a pesticide product, after “danger” and “warning.”

“It is a very safe product for the tree, as long as it’s used by someone who knows what they’re doing. It’s not a poison.”

Daphne Richards, Texas A&M AgriLife Extension Service

The label for Cambistat, one of the products registered with the EPA and has Paclobutrazol as an ingredient, warns the product can be “harmful if swallowed, inhaled or absorbed through the skin.”

  • Read more about how the EPA labels pesticide products and chemicals here

It also states: “Avoid contact with skin, eyes, or clothing. Avoid breathing spray mist. Wash thoroughly with soap and water after handling and before eating, drinking, chewing gum, using tobacco, or using the toilet. Wear long sleeved shirt, long pants, socks, shoes and gloves. Remove and wash contaminated clothing before reuse.”

The label goes on to note that it should not be used on fruit or nut trees that will be harvested, should not be applied directly to water and could affect surrounding vegetation.

Richards said that’s why she suggests people always discuss their backyard and their options with their utility provider.

“‘This tree is near this situation.’ And ‘which tree do you mean?’ I think all of that is very good information to have,” she said. “The more context we give people, the more information they have, the more they feel comfortable with the process, which is just as important as the process itself.”

The Pedernales Electric Cooperative spokesperson noted before using the product on any of their members’ properties, PEC always provides advance notice and information, as well as the opportunity to speak with one of their vegetation experts in order to any questions. Members can also choose to opt out of the program.

Cassandra said his real concern was the opt-out nature of PEC program. He said he hopes his neighbors had time to do their own research and decide for themselves.

“So if I happened to be on vacation for a week or two, they could have come and treated, and I would never have known,” he said. “This pamphlet is not enough to make me make an educated decision, because its one sided.”

According to the PEC website, crews go door-to-door and will leave a door notice with their contact information on it if you are not home. If you have a water supply within 100 feet of the right-of-way or have any other questions or concerns, it said, be sure to contact them within five business days.

“If five days have passed, and they have not heard from you, the application will take place as planned, without any further notice,” it read.

Cassandra said PEC had previously been communicative about tree trimmings, including sending flyers, emails and letters in the mail about the upcoming work. He has been in contact with PEC about his concerns about tree growth regulators, and he was able to opt-out of the program.

According to its website, PEC also still trims and prunes when appropriate. The spokesperson said, “vegetation management is key to preventing power outages and helping crews restore power, as quickly and safely as possible.”

  • Read more about PEC’s vegetation management plan here

Austin Energy, which provides power to the majority of the city, said it also uses these kinds of products but in a “very limited” manner. In early February, Vice President of Electric System Field Operations Elton Richards said it will coat the limbs that have been cut to prevent growth in rare circumstances. More often than not, he said, Austin Energy uses this product for vine control, not on trees.

“We try to stay as far away from chemicals as possible,” he said.

According to a KXAN report in February, Austin Energy trimmed trees along nearly 300 miles of distribution lines, in part due to an increased vegetation management budget.

  • Read more about Austin Energy’s vegetation management plan here