Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS

Episodes
Dangerous Catch Dirty Secrets Additional Episodes
border
TV Schedules About the Project For Educators Feedback border
border
National Geographic's Strange Days on Planet Earth
Get Involved
Little changes... with big results. border
border
INVADERS
border Why Should I Care? border border

5 Reasons Why

Why Others Care
border What Do Experts Say? border border

From the Episode

Related Stories

Resources
border How Do I Measure Up? border border

Tools You Can Use

Interactive House
border What Can I Do? border border

Get Out There

Idea Exchange

Please note that links marked with Off-site Link are off-site links and will open in a new browser window.

PBS's Terms of Use.

Lake Victoria's Water Hyacinth Problem

No one's sure how the South American water hyacinth invaded Africa's Lake Victoria but there's little doubt as to the damages it has caused. In 1989, the weed was spotted in the lake and seven years later, it had clogged 80% of Uganda's shoreline. Freed from its natural insect enemies, it continued to spread. Getting to fishing grounds became a terrible struggle. A reduced catch and lowered income threatened to trigger widespread famine. Rotting vegetation, under the suffocating blanket of weeds, began to foul drinking water — which comes straight from the lake. Meanwhile, along the edges of the floating weeds, water snails harboring the deadly schistosomiasis parasite found a new place to breed. James Ogwang decided to spoil the party.

What makes you most hopeful for the future?
James Oswang Ogwang: "...by integrating use of biocontrol agents in pest management, Planet Earth will remain a healthier environment with a relatively intact biodiversity for generations present and future..."

See James Ogwang's full Q&A »

Ogwang imported another invasive species — a voracious South American weevil and natural enemy of water hyacinth. Ogwang tested to see if his new tiny imports would keep their sights solely on the water hyacinth and not on any local crops. Satisfied with their specificity, he released his tiny army and they got to work.

Water hyacinth is a problem in the US as well. According to the University of Florida, water hyacinth was introduced from South America into the US in 1884. Since then it has spread into many lakes and rivers of the southern US, making it one of the most troublesome aquatic plants in the country.

A number of different biocontrol species have been tested on water hyacinth here in the US. In 1972, the mottled water hyacinth (Neochetina eichhorniae), with a life span between 90-120 days, was deployed in Florida. In 1974, a shorter life span weevil, the chevroned water hyacinth weevil (Neochetina bruchi) was released. Later, an even shorter life-span hyacinth eater — the Argentine water hyacinth moth (Sameodes albiguttalis) with a lifespan of only 30 days — was established. These species have now been used not only in other states like Louisiana and Mississippi but across the world including such countries as Australia, Fiji, Honduras, India, Malaysia, Papua, South Africa, Sudan and Thailand.

Related Links
» The University of Florida Off-site Link offers more information on controlling invasive plants with biocontrol.

Next: Miconia Invasion of Hawai'i »


Site Credits   |   Privacy Policy
© Copyright National Geographic Television & Film. All rights reserved.