Cotton Seedlings From Fungal Attack
By Alfredo Flores
May 20, 2002
When planting the Sure-Grow 747 cotton
variety last year, Agricultural Research
Service plant pathologist Charles R. Howell was confident that his
seedlings would grow just fine under ideal planting conditions. Much to his
surprise, his cotton seedlings did not emerge.
The culprit? A damping-off disease caused by Rhyzopus oryzae, a close
relative of common bread mold. Its a disease few growers know about, even
though it can strike during a typical growing season. In most cases, the
disease causes plants to perish before they rise above ground. The few plants
that emerge do not live long because their roots rot.
Howell, based at the ARS Cotton Pathology
Research Unit at College Station, Texas, doubts that many farmers realize
when this particular problem is happening. They just chalk it up to ordinary
cotton seedling disease.
To make matters worse, typical seed treatment fungicides arent
effective against R. oryzae. For example, there is another more common
pre-emergence damping-off disease, caused by the mold Pythium ultimum,
that also can be fatal to cotton seedlings germinating under very damp soil
conditions. But the seed treatment fungicide normally used to control P.
ultimum has no effect on R. oryzae.
To solve this problem, Howell has devised a biological control treatment
using the fungus Trichoderma virens. It is grown in liquid cultures,
then the solids are dried and ground up. When applied in granular form, this
agent controls both P. ultimum and R. oryzae on cotton seed by
preventing germination of these molds.
Howell has been working on this project since 2000 and now is talking to
crop protection product companies to see if they are interested in
commercializing his new product.
According to National Cotton Council
data, nearly 2.5 percent of the estimated loss in U.S. cotton bales in 2001 was
due to seedling diseases, at a cost of approximately $170 million. It is
unknown how much of this may be attributed to R. oryzae.
ARS is the U.S. Department of
Agriculture's primary scientific research agency.