Infective stages (spores) of a microsporidian
pathogen that infects the beneficial weevils Neochetina bruchi and N.
eichhorniae. Click the image for more information about it.
story to find out more.
Cause of Disease in Beneficial Insects
By Jim Core
April 16, 2004
The mystery behind the decline of
beneficial biocontrol weevils that help control the invasive weed water
hyacinth in Florida has been solved by Agricultural Research Service scientists.
They've found that a microorganism is responsible for killing the weevils and
reducing their reproductive capacity.
The two closely related South American weevils, Neochetina eichhorniae
Warner and N. bruchi Hustache, have been used since the 1970s to
control water hyacinth, an aquatic weed that clogs waterways, displaces native
vegetation and degrades wildlife habitats in Florida. The weevils are
mass-reared and, once released, feed on the weed and help to keep it from
spreading. But recently, the effectiveness of the weevils has been declining
for unknown reasons.
James J. Becnel, a research entomologist at the ARS
Center for Medical, Agricultural and
Veterinary Entomology in Gainesville, Fla., and Theresa Rebelo, a
postdoctoral researcher from Portugal, worked with the ARS
Plant Research Laboratory in Fort Lauderdale, Fla., to determine what was
wrong with the weevils.
The scientists suspected that a disease caused by a microorganism, called a
microsporidium, was responsible. Tests determined that a recently discovered,
still unnamed microsporidium was decreasing weevil survival rates by 30 percent
and was reducing the weevils' reproductive capacity--one species by 72 percent,
the other by 62 percent.
According to Becnel, the study's findings demonstrate the importance of
selecting disease-free organisms for biological control programs. If it's
determined to be economically practical to treat weevil colonies, researchers
will work at developing a method to cure them of the disease.
more about the research in the April issue of Agricultural Research
ARS is the U.S. Department of
Agriculture's chief scientific research agency.