The southern green stink bug is a culprit in
passing along a seed rot disease in cotton. Photo courtesy of Russ Ottens,
University of Georgia, Bugwood.org. |
|
ARS Research Explains Link between Stink Bug,
Cotton Disease
By
Dennis O'Brien January 21, 2009
A mystery about a disease that can destroy up to 15 percent of a
cotton crop in the southeastern United States has been solved by
Agricultural Research Service (ARS)
researchers. The work could save cotton crops and prevent unnecessary
insecticide spraying.
In 1999, scientists reported an emerging seed rot disease that was
discoloring seeds and darkening fibers in cotton bolls in the southeastern
states, making the crops unmarketable. It quickly spread throughout the
southeastern Cotton Belt.
To study the problem, plant pathologists
Gino
Medrano and
Alois
Bell of the
ARS
Cotton Pathology Research Unit, part of the
Southern
Plains Agricultural Research Center in College Station, Texas, focused on
the southern green stink bug (Nezara viridula L.) as the disease-transmitting
culprit.
In the greenhouse, they infected cotton bolls with suspect bacteria,
using a needle to penetrate the boll wall and mimic a stink bug's bite. The
results showed the needle created a pathway for the bacteria to enter the boll
and damage it.
The researchers used a strain of the bacterium Pantoea agglomerans in
the research, but other bacteria may also be involved in damaging cotton
plants, according to the scientists.
In other tests, Medrano and entomologist
Jesus
Esquivel of the
ARS
Areawide Pest Management Research Unit in College Station showed why stink
bugs sometimes--but not always--cause extensive damage in cotton fields. By
infecting bolls at various stages, they found damage levels depend on when
infections occur in the fruiting cycle and on how long infection is allowed to
spread before harvest. Bolls infected three weeks after flowering are resistant
and undamaged. Younger bolls remain susceptible.
Farmers often spray insecticide to combat stink bug infestations. But
knowing mature bolls are immune to infections should help farmers decide when
to spray. Medrano also is developing a test kit that will offer guidance by
telling farmers if stink bugs in their fields are infested with the pathogens
that cause the seed/boll rot.
A report on Medrano's work appeared in a recent issue of the Journal of Economic
Entomology.
ARS is a scientific research agency of the
U.S. Department of Agriculture.