Looking at soybean disease treatments


There are some new fungicide seed treatments for soybeans recommended for Ohio farmers.
Ohio’s poorly drained soils are particularly favorable for the group of pathogens known as watermolds,
Pythium spp. and Phytophthora. We have documented two species of Phytophthora that infect soybean, Ph.
sojae (the most famous) and Ph. sansomeana. There are many Pythium spp., more than 30 that we have
recovered and confirmed as pathogens of soybean in Ohio. Historically, metalaxyl and mefenoxam were the
two seed treatments that targeted the watermolds, but in Ohio; there are a number of Pythium populations
that are resistant or have reduced sensitivity to these compounds. The strobilurin fungicides
(azoxystrobin and pyraclostrobin) have activity towards some Pythium spp. but not all. There are now two
new fungicide seed treatments on the market, ethaboxam and oxathiopiprolin.
Ethaboxam was developed by Valent and it has very good activity towards Phytophthora sp. and a good
proportion of the Pythium spp.. Oxathiopiprolin was developed by DuPont and it has very good activity
towards Phytophthora.
For the true fungi, again the theme is that no one fungicide will cover all the bases. Two examples of
this are sedexane, which is for Rhizoctonia only and the newly registered material, fluopyram which
targets Fusarium virguliforme, the sudden death syndrome (SDS) pathogen. Fusarium graminearum has been
associated with poor stand in Ohio, especially in fields with high levels of corn residue. Pay
particular attention to this if the field has had a history of head scab on wheat or Gibberella ear or
stalk of corn. This pathogen can infect and cause disease on all three crops.
More information can be found at http://corn.osu.edu then search for newsletter 2017-1.

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