MDC says avoid spreading invasive species like hydrilla

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Kansas City
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Kansas City, Mo. – Invasive aquatic plants and animals cause major problems for anglers and boaters, and swimmers. The Missouri Department of Conservation (MDC) says with care citizens can help avoid the spread of harmful invasive species. Prevention is usually easier than the cure, especially with a challenging invader like hydrilla.

MDC is currently helping Powell Gardens battle hydrilla, a highly invasive aquatic plant that can reproduce in multiple ways and completely clog ponds and lakes. Hydrilla apparently arrived at the main lake at Powell Gardens in the soil of potted water lilies originating in Florida. The water lilies were purchased from a dealer and planted as an ornamental flower in the lake. Hydrilla apparently hitched a ride among the water lilies. An alert citizen visiting an MDC display about invasive species at last summer’s Missouri State Fair recognized that hydrilla was in the lake at Powell Gardens, which is in Johnson County east of Kansas City.

“Hydrilla can be very detrimental,” said Trish Yasger, MDC fisheries management biologist. “Florida and Texas are spending millions of dollars each year fighting hydrilla. It gets so thick you can’t get a boat through it. And it gets so thick that sport fish don’t do well. It’s just not good.”

All types of native fish, plants and insects are at risk from a hydrilla infestation. So is a property owner’s enjoyment of ponds, lakes and streams for recreation. The green plant's leaves have fine-toothed, serrated edges, which helps distinguish them from other common but less harmful aquatic plants. The leaves grow in a whorl around a stem.

This summer, MDC will be contacting landowners near Powell Gardens in Johnson County to seek permission to inspect ponds or lakes for hydrilla. The noxious plant has appeared at a few other sites in Missouri, where MDC also is working with property owners to eradicate it. MDC will coordinate treatment efforts for hydrilla with property owners.

Hydrilla arrived from Asia or Eurasia in the United States in the 1950s in the aquarium trade. The plant can grow an inch a day and double its biomass every two weeks during peak summer growing season. But the water weed’s multiple ways to reproduce pose extra challenges in eradicating it or halting its spread.

A piece of a hydrilla plant can start a whole new colony, thus pieces moved by birds or boats can spread it. Each plant produces many bud structures called turions that can start new plants, and each plant can start a colony. Especially problematic is that each plant produces multiple tubers, similar to how potatoes develop, and these can start new plants.

Eradication efforts involve applying herbicide that kills hydrilla plants. However, the herbicide does not affect the tubers at the bottom of a lake. Those tubers can survive for up to five years. So treatments must be continued for that long to eradicate hydrilla.

Despite these challenges, MDC biologists believe the plant can be eradicated if outbreaks are treated promptly. Hydrilla has also been found and treated at sites in Greene, Dallas and Warren counties.

“If hydrilla gets into a lake like Smithville, Truman or Lake of the Ozarks, it could be devastating,” Yasger said. “The quicker we find hydrilla before it makes lots of tubers, the quicker we can eradicate it. Unlike Florida and Texas, we don’t have a lot of it, so we think we can get rid of it. The sooner we get it under control, the better chance we have to eliminate it. If we can treat it when it first appears, chances are it hasn’t had a chance to set down all those tubers, making it easier to treat.”

The steps boaters, anglers and water gardeners can take to prevent hydrilla are the same as for preventing the movement of other invasive species, such as zebra mussels.

  • Boats, motors, and trailers should be drained, cleaned and dried before moving them from one body of water to another.
  •  Don’t dump bait buckets.
  •  Inspect boats and trailers for mussels or plants before moving them.
  • Before planting ornamental aquatic plants in water gardens, make sure roots are bare and clean.

Also key, citizens should not dump aquarium fish and plants into any body of water. This is especially a problem in cities and urban areas. Some forms of hydrilla are still being sold in the aquarium trade. Some pet supply shops will accept fish and plants that an owner no longer wants to care for.

For information about hydrilla in Missouri, and for photos to help identify the aquatic plant, visit   Anyone concerned that hydrilla is present in their pond can contact their local MDC office. To talk with MDC’s Trish Yasger about hydrilla, call 660-530-5500, or email at Photos sent by email may be helpful in identification.