As chemical and mechanical removal is often too expensive, polluting, and ineffective, researchers have turned to biological control agents to deal with water hyacinth. The effort began in the 1970s when USDA researchers released into the United States three species of weevil known to feed on water hyacinth, "Neochetina bruchi", "N. eichhorniae", and the water hyacinth borer "Sameodes albiguttalis". The weevil species were introduced into the Gulf Coast states, such as Louisiana, Texas, and Florida, where thousands of acres were infested by water hyacinth. It was found that a decade later in the 1980s that there was a decrease in water hyacinth mats by as much as 33%. However, because the life cycle of the weevils is ninety days, it puts a limitation on the use of biological predation to efficiently suppress water hyacinth growth. These organisms regulate water hyacinth by limiting water hyacinth size, its vegetative propagation, and seed production. They also carry microorganisms that can be pathological to the water hyacinth. These weevils eat stem tissue, which results in a loss of buoyancy for the plant, which will eventually sink. Although meeting with limited success, the weevils have since been released in more than 20 other countries. However, the most effective control method remains the control of excessive nutrients and prevention of the spread of this species.