Surfacing this summer

Diving into water management means controlling a diverse range of weeds that can devastate a pond or aquatic body. Unfortunately, applying that control incorrectly could also spell irreparable harm to a complex ecosystem.

“From the landscaper side of things, often times, one of the first things we tend to run into is a general misunderstanding of how aquatic plants goes,” says Stephen Enloe, a professor at the University of Florida and invasive plant extension specialist. “This is not simply going out and applying management.”

Uneducated landscapers working in water management can cause massive fish kills, harm to birds or the loss of other aquatic plants. Understanding basic aquatic biology can help landscapers prevent common mistakes. These include weed misidentification and applying the wrong control; applying the wrong treatments at the wrong time of year; and being too reactionary with chemical control.

That’s not to mention that all sorts of invasive weeds are spreading nationwide as a result of aquarium trade and boating across state lines. Karin Kettenring, an associate professor of wetland ecology at Utah State University, adds that mud on construction or landscaping equipment can transfer some of those seeds to different bodies of water, too.

“Be careful to not be a part of the problem,” Kettenring says. “We’re talking about transportation soil and dirt on machinery, so there are protocols on best practices for cleaning equipment.”

Kettenring joined Enloe and Brittany Chesser, an aquatic vegetation management program specialist, in explaining ways landscapers can approach weed control in the water. Plus, they offered examples of some of the weeds they expect to surface this summer.

The right thing

Texas is home to a wide variety of ponds — 1.3 million of them. An influx of people moved to the state during COVID-19, and cattle and livestock owners use those ponds for watering. In the meantime, Chesser — with the department of rangeland, wildlife and fisheries at Texas A&M — has seen livestock trampling down slopes and dragging in different vegetation. Plus, there’s that patented Texas heat.

“When it’s a long, hot day, and you have cattle waiting in that pond, they’re constantly dropping nutrients in the water,” she says, adding that Texas has had some extreme drought conditions over the last two years. “We’re constantly losing water through evaporation throughout the summer. What some people don’t realize is that when we’re losing the water, those nutrients aren’t evaporating. They’re staying in that pond and they’re compounding.”

So, for those working with water, doing the right thing matters. Everything they do in these ponds dramatically affects the watershed and vice versa. Chesser says that learning different types of management is essential for those working in landscape construction, too.

That’s not just important in the southeastern United States. In Florida, Enloe says the preferred method of control has been chemical treatments, but there are other options that are worth considering like mechanical harvesters for bigger bodies of water. Doing the research to find the right biological controls, like grass carp, can help keep aquatic weeds at bay, too, as they feed on some submerged aquatic plants and some floating plants. Landscapers would require the right permits in Florida to introduce this control into a body of water, so that’s likely true in most other states as well. They’re also subject to predation, so managing the biological controls can be a pain.

There are also lake lawn mowers for those larger spots, or there’s always the option to hand pull. Enloe says this is often exhausting though.

“People can do that on extremely small scales, but even on a pond on a tenth of an acre, you can wear yourself out pretty fast,” he says.

So, that means herbicides get the most “bang for your buck,” Enloe says. But the number of available herbicides is slim compared to options available in the turfgrass world. The two active ingredients that are most common are diquat and glyphosate. It’s hard to get more approved beyond that.

“They’re subject to extensive aquatic testing prior to EPA approval,” Enloe says. “We have to do a lot more due diligence on the safety, what its persistence is going to be, are you going to have problems irrigating? All of that information has to be vetted very rigorously.”

It’s a good thing there’s rigorous testing, Enloe adds, because incorrect water management is so damaging. There’s also a great deal of negative public perception, especially around the ingredient glyphosate, the subject of a number of notable lawsuits over the last decade. But he’s still recommending it as a treatment option when used properly.

“The reality of it is, if the science changes, I’m going to be the first one waiving the red flag,” Enloe says. “Until that happens, I’m not going to be reactionary.”

Chesser reiterates the point that there’s less options available for those working in the water. She says there are much more restrictions because water can easily flow in to public water bodies or to your neighbor’s properties in a flooding event. “Our toolbox is pretty limited, so you have to be pretty mindful of that. There’s no silver bullet,” she says.

“I think the number one thing is, (you should) realize you’re not working with a two-dimensional system. You’re looking at a one-surface acre pond, but there’s a lot going on underneath that,” she adds, saying that’s going to make a huge difference to anyone trying to manage something. “We talk in terms of acre feet, which is surface acres versus surface depth.”

Out west, in Utah, Kettenring recommends landscapers follow best practices and immediately clean equipment before leaving a jobsite. She also points landscapers toward their local university’s extension programs, which help dispense valuable public information. It’s there they’ll have pamphlets, websites, YouTube videos and personnel focused on aquatic invasives.

“Be aware of best practices and don’t be a part of the problem,” she says.

The worst of the weeds

Enloe says there’s a number of species that fall under floating plants and a plethora of water hyacinth and giant salvinia, an aquatic fern that’s capable of tremendous vegetative reproduction. They’ve seen that one spread across the southeast in recent years, and it’s a particular worry for those studying aquatic weeds.

“It’s one of tremendous concern because it’s one of these species that tends to layer across itself,” he says. “They can cause major ecosystem change.”

He adds that hydrilla water weed is a classic submersed plant that’s been a problem in the southeastern United States, but over the last 10 to 20 years, it’s appeared northwards, as far north as Michigan. Without great biological controls, and the fact fishermen love hydrillas because they feed the fish, it can be a tricky weed to mitigate.

“These things are not all the same, but they are finding their niche in waters farther and farther north,” Enloe says. “That’s going to be a really big problem for a lot of the country that’s simply not ready for it.”

Enloe says milfoil, a submersed species, is now prominent across the northern tier of the U.S. “We’re learning that some of the hybrids can be more aggressive than the Asian water milfoil,” he says. “I expect the hybrid version to be a big problem across the northern tier United States.”

Meanwhile, flowering rush, which reproduces so many different ways, is becoming a bigger problem because of how easily it spreads. Enloe also referred to floating heart and alligator weeds as common issues landscapers will need to thwart this summer.

Chesser jokes that the running gag between those in her department is that at least they’re not Florida — there’s so many issues in that state that are still spreading elsewhere, but they’re not quite elsewhere yet. She says algal blooms can be tricky because people often think their ponds are self-sustaining when they see those algae mats, when in actuality, fish kills could be happening below the surface.

“Aquatic vegetation is the number one reason for oxygen fish kills,” she says.

Kettenring says the reason coastal states experience more pressures is due to how much international trade and travel exists in those spots with more ports. It’s encouraging for land-locked states that this won’t change, but there are still problems like curley-leaf pondweed that are troubling.

Kettenring adds that invasive species like quagga mussels are worth looking out for, too, but the encouraging thing is that states are becoming more aware of these issues. They have checkpoints and protocols across state lines. It’s all about managing the vectors carrying any of these weeds or species.

“They’re not totally out of control in these regions,” she says.

The author is an associate editor with Lawn & Landscape magazine.