Lincoln, Nebraska
November 26, 2008
Source:
CropWatch August 26, 2008
One management practice available
for certain soybean diseases is the use of resistant soybean
varieties. As you make your seed selections, consider using
resistance in your soybean seed if you have one of the following
problems. Always make sure to select agronomic characteristics
to match your ground and conditions as well.
Soybean Cyst Nematode
(SCN)
Soybean cyst nematode is
spreading and has now been observed across the eastern third of
Nebraska. Each year newly infested fields are identified. This
disease, caused by the nematode Heterodera glycines, can be a
problem anywhere, but has been found more frequently near
waterways.
Once identified in a field it
is critical that SCN-resistant varieties be utilized in a
rotation system so that the population (number of nematodes per
unit of soil) does not reach a level that makes soybean
production unfeasible.
It’s also important that the
source of SCN resistance be rotated. This is necessary because
the nematode population can adapt to the resistance source and
overcome its effects.
For more information on soybean
cyst nematode, including symptoms and how to sample a field, see
NebGuide G1383,
Soybean
Cyst Nematode Biology and Management.
Phytophthora Root and
Stem Rot
Phythophthora root and stem rot
was a problem in many fields in 2008 as a result of wet
conditions. This disease is caused by the fungus Phytophthora
sojae and has been found throughout Nebraska soybean production
areas. This disease is primarily a problem in fields with poor
drainage or soils with high clay content that maintains high
moisture levels. In many Nebraska fields, the biotypes of
Phytophthora can be defeated with commonly marketed resistance
genes in commercial varieties.
Several sources of resistance
are sold in Nebraska: Rps 1k (most common), Rps 1c (second most
common) and Rps 1a and Rps 3 (limited availability). In some
cases the biotype of Phytophthora in the field may be resistant
to a source and the product will be ineffective. In surveys we
have identified several fields with such biotypes. In these
cases it is critical that good tolerance to Phytophthora be
utilized along with increased rates (high end of label range) of
seed treatment fungicides containing mefenoxam.
For more information on
Phytophthora, including how to identify and manage this disease,
see G1785,
Management of Phytophthora Root and Stem Rot of Soybeans. |