Man versus plant

A local biologist employs tiny allies in his battle against the lovely yet destructive water hyacinth

A volunteer with the Willow Creek Water Hyacinth Removal Project, with his quarry in hand.

A volunteer with the Willow Creek Water Hyacinth Removal Project, with his quarry in hand.

Photo by Ken Davis

It is an unlikely wilderness, this area of Folsom packed with car dealerships, glass and steel office buildings, and acres of asphalt parking lot.

But if you look more closely, and you’re willing to get a little wet, you’ll find a hidden oasis of natural habitat meandering among the corporate campuses.

These are two of Folsom’s urban creeks, Willow Creek and its smaller cousin, Alder Creek. Both are damaged by decades of urban pollution but, remarkably, they are getting healthier and providing a home to an impressive array of native plants and animals.

As biologist Ken Davis tromps through the stream bed in rubber waders, an unsteady reporter in tow, he points out the obvious signs of life in this hidden wilderness. Here is otter scat, the tracks of raccoons, and beaver dams. Ducks are in abundance, flying low overhead and landing on the water.

But Davis is on the trail of something more sinister than beaver. He is seeking (and destroying) an unwelcome invader that has taken up residence in these creeks: the lovely but destructive water hyacinth. And he plans to attack his enemy with an army of Brazilian bugs called weevils.

Tenacious enemy
Davis’ quarry isn’t hard to find. A few twists and turns along the shallow creek, and you confront a pool that has been completely taken over by the plant—a vast, strangled mat of thick, green, polished-looking leaves and purple flowers. The striking color and lushness give it a sort of tropical beauty that belies its true nature as a tenacious pest wrecking the local environment.

“It’s biological pollution,” Davis lamented.

Davis manages the Willow Creek Water Hyacinth Removal Project, a partnership of the state Department of Water Resources, the city of Folsom, and Davis’ own organization, the Wildlife History Foundation, a group that specializes in environmental education.

The project has two goals. First is to get the hyacinth out of area waterways—which has required some creativity. The second goal, in some ways a more difficult task, is to educate the public about how they can help stop the spread of the noxious weed.

Because it grows so fast and thick—a single patch of it can double in area every 12 days in hot weather—water hyacinth easily chokes out native plants. It makes it incredibly difficult for animals to negotiate streams and forage, and when it dies, the bacteria that feed on rotting plants can rob all of the oxygen from a pool, killing fish and invertebrates in the water. Hyacinth also increases flooding by clogging up these little streams, and can turn free-flowing channels into stagnant breeding grounds for mosquitoes.

The plant hails originally from Brazil and got its foothold in this country decades ago on the American southeast, working its way west to Texas and even to the Sacramento-San Joaquin Delta, where it plays havoc on Delta streams and sloughs. The infestation here probably got its start when some (presumably) unsuspecting homeowner decided to clean out his or her backyard koi pond and tossed the extra plants into a nearby stream.

Because it is an alien, hyacinth has no natural enemies locally that can keep it in check.

Photo by Ken Davis

Davis fears that it is only a matter of time before it spreads out of this immediate area. He has spotted it and removed it from nearby Lake Natoma. If allowed to go unchecked, it could even find its way into the American River. Although it isn’t likely to thrive in the faster, colder water of the river’s main channel, it would probably find the American’s myriad warm shallow sloughs quite cozy indeed.

So, Davis and his volunteers spend much of their time scrambling in and around these creeks, pulling hyacinth out by hand—a back-breaking task that often requires hauling inflatable rafts full of hyacinth through densely overgrown stretches of the creek. They also spend time surveying other areas of the creek, making sure no new infestations crop up, which they often do.

The work is paying off. Davis said he has seen the return of some local wildlife that hasn’t been spotted in years, like pond turtles, ducks and larger birds, herons and kingfishers.

“It’s incredible. I’ve never worked on a project where the results have been so apparent,” Davis explained. “If you really want to help a creek, get the water hyacinth out,” he added.

As difficult as the hand removal is, “the biggest, most important problem is education.” Many people, he said, don’t know the damage that hyacinth can do if they toss it into a creek. He even occasionally has people come up to him while he is working and ask to take some of the hyacinth home with them. He refuses.

Not that it’s hard to get a hold of. You can buy hyacinth plants at local nurseries for about $1.50 a plant. When asked how to go about “planting” it, an employee at one local nursery replied, “Just throw it in the water, it grows pretty fast.”

Some states, like Texas, have laws prohibiting the sale of the plant. A year ago, state Senator Deborah Ortiz introduced similar legislation, but it appears that it was lost in a torrent of higher-priority legislation and was forgotten about—never even heard in committee.

Enter the weevils
It would take years for Davis and other volunteers to rid these creeks of hyacinth by hand. In other areas, such as the Sacramento-San Joaquin Delta, crews have attempted to kill it by spraying it with herbicide, with limited success. Here, just getting the permits to spray would be cumbersome. More importantly, Davis said, spraying poison in the creek is far from ideal.

So with help from the state Department of Agriculture, Davis is calling in the cavalry—in this case, a battalion of weevils that hails from the Amazon. Unlike the hyacinth, hyacinth weevils are ugly, dull brown and a little bit tick-like.

Their beauty is in their function. These bugs are the natural enemies of water hyacinth. They lay their eggs inside the thickest part of the plant, where the larvae proceed to eat the plant from the inside out.

This “biocontrol” approach may be perfect for these plants and the specific challenges of restoring an urban habitat.

It may seem dicey to introduce yet another exotic species into the local environment. But Davis says not to worry. The weevils, which should arrive any day, have been tested for years to make sure they don’t pose a threat to their new habitat.

It seems the weevils evolved to eat water hyacinth, and only water hyacinth. When the hyacinth supply dips, so does the weevil population, so each species keeps the other in check. That could slow the plants’ spread enough to make pulling it out by hand a lot easier.

“If we get the right bugs they should do really well,” Davis explained. “This is the perfect spot for biocontrol.”