Harmful Aquatic Hitchhikers: Plants: Hydrilla

What does Hydrilla look like?

Hydrilla is a submersed freshwater herb. Being an invasive non-native weed, it often forms dense stands from the bottom to the top of the water, sprawling across the surface, although it may also be found as detached drifting mats.

Why is Hydrilla considered to be a nuisance?

• Once cultured and sold as an aquarium plant, it is hydrilla’s invasive qualities that make it a nuisance.
• It has amazing reproductive capabilities that allow it to grow in almost any freshwater, in variable conditions with either low or high nutrient amounts, or a wide temperature tolerance: (68-86 F).
• Hydrilla is an invisible menace until it fills the lake or river that it infests, "topping out" at the surface.
• When hydrilla invades an area, ecologically important native, submersed plants are shaded out by hydrilla’s thick mats, or are simply out competed and eliminated.
• Annually, millions of dollars are spent each year on herbicides and mechanical harvesters in Florida alone in an effort to place hydrilla under "maintenance control." Besides the impact to recreational fishing, Hydrilla greatly slows water flow and clogs irrigation and flood-control canals. In Florida, large mats of fragments collect at culverts and clog essential water control pumping stations. Hydrilla seriously interferes with boating, both recreational and commercial, and prevents swimming and fishing. Major infestations limit sportfish weight and size due to the plant’s ability to alter water chemistry and oxygen levels.

How does Hydrilla affect recreational users?

Due to its nuisance impacts, Hydrilla affects all recreational users of our aquatic resources. Its amazing reproduction capabilities can turn quality waters into areas that are choked with vegetation, which will essentially make them unusable.

Where is Hydrilla currently found?

Currently, this plant is found primarily in two regions, the southeastern and the southwestern parts of the U.S.

What is Hydrilla’s potential to spread elsewhere in U.S.?

Hydrilla spreads to new waters mainly as fragments on boats and trailers. Conservationists in the U.S. need to learn from Russia experience because hydrilla has been found to grow in 50o N latitude range, which is the equivalent to the US/Canadian border.

Short term benefits of hydrilla don’t override the long term impacts

Some anglers originally thought that plants such as hydrilla and water hyacinth provided positive habitat. However, anglers now realize that these plants can take over a good fishing spot, consume the oxygen and cause fishkills. Also, when hydrilla creates mats, it can make it very difficult for anglers to access fishing spots.

How can I prevent the spread of Hydrilla?

Be vigilant in cleaning your equipment.

What else can I do?

• Follow procedures to eliminate the spread of all nuisance species.
• Help inform others.
• Get involved in policy and legislative solutions.

This infomation was provided by the U.S. Fish and Wildlife Service. For more information, go to their campaign website www.protectyourwaters.net.