Looks That Kill

A beautiful flowering plant from the Amazon is suffocating America's waterways.

Looks certainly are deceptive. The lush leaves and flashy flowers of the water-hyacinth (Eichhornia crassipes), for example, have for centuries caught the eyes of Amazon Rainforest visitors, who often collected the plant for decoration. But since the late 1800s, this attractive aquatic herb has literally taken over the world's waterways, and has become one of the most persistent pests in the Americas, Asia, Australia, and Africa.

Away from the insects and microbes that keep it in check in its native habitat, water-hyacinth has spread in other parts of the world with unbridled success. With a growth rate among the highest of any plant known-in water, or on land-populations may double in less than two weeks. Plants float on the water's surface in dense mats that clog waterways, decreasing dissolved oxygen and suffocating other aquatic plants and animals.

But scientists are fighting back. In California - where water-hyacinth occurs throughout the central valley - the beautiful invader has been controlled by employing hyacinth-eating weevils and moths, herbicides, and good old-fashioned muscle power. And in the last couple of years, an international group of scientists has gone to the source of the problem-the upper Amazon-to track down an army of natural enemies to assist in the global battle.


Introduced to the United States in the 1800s, water-hyacinth today thrives in 16 states from coast to coast. Photos: Robert Potts, CAS. Inset: Jeff Abbas.
Riverbank in Tracy (San Joaquin County, California, US) Boats are pushing the weeds to dragline and conveyor for removal.
Photo: Staff CDFA, California Dept. of Food & Agriculture, Integrated Pest Control Branch