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Scouting this Growing Season… Diseases
By Justin Petrosino
ANR Extension Educator
OSU Extension, Darke County
Last week we discussed a few pesky bugs that have been and may continue
to be a problem in our major crops. This week we’ll talk about some
diseases we’re keeping an eye on. Let’s dive in with the one that is
still on everyone’s mind, head scab. Why was it such a problem last
season? We fulfilled our disease triangle. We had inoculum from
previous infection of corn, we had warm, wet weather at flowering, and
we had a lot of susceptible varieties planted. The big question is will
it happen again? The answer is maybe. If we meet those three criteria I
listed previously it may come back again. If you caught my article last
July or read the CORN newsletter you will already be ahead of the game.
As a refresher to reduce the impact of head scab you should avoid
rotating corn to wheat or vice versa. You should also plant varieties
that are less susceptible to scab. If we do see warm, wet weather
during wheat flowering a fungicide may be beneficial if it is timed
correctly. However, our best fungicides, Metconazole, Prothioconazole,
and Tebuconazole are only rated fair to good on scab. We do not have
any fungicides that are labeled excellent for control.
In soybeans we have several seedling rots that can take a toll early in
the season. Phytopthora and Pythium have similar management strategies
and tend to show up in poorly drained or compacted areas. Management
includes improving drainage if possible, increasing rotation intervals
out of soybean, and use of seed treatments containing metalaxyl and
mefenoxam. Phytopthora can also be managed by planting resistant
varieties. If you plan on using a seed treatment as a part of a
management plan for Phytopthora, the treatment must contain a
full rate of either of the two products to be effective. If you are
unsure which disease you are fighting, you can find more information in
OSU Extension’s bulletin 827, the Corn, Soybean, Wheat, and Alfalfa
Field Guide. Still unsure, you can submit a sample to the C. Wayne
Ellett Plant and Pest Diagnostic Clinic. For more information on
submitting samples contact Justin Petrosino, OSU Extension, Darke
County at (937) 548-5215 or the Diagnostic Clinic directly at (614)
292-5006.
Another soybean disease on the rise is Sudden Death Syndrome. This
disease tends to pop up when wet weather follows planting and when
soybean cyst nematode levels are high. Although we see intervenal
chlorosis and necrosis on the leaves, sudden death is actually a root
disease. With sudden death digging up the plant will reveal rotted
roots and possibly a blue hue to the taproot. This is actually the
fungus growing on the root. Management for SDS may seem redundant after
reading the last few paragraphs but planting resistant varieties,
improving drainage, and increasing crop rotation can help. Also, since
it is correlated with soybean cyst nematode, reducing nematode
populations with rotation and resistant varieties can help.
If I were to cover every disease we deal with in Ohio I could easily
take a whole page of the newspaper. There are twenty for wheat alone!
To learn more about these diseases or get more agronomic information,
visit the AgCrops website at agcrops.osu.edu/.
There you will find information on diseases, insects, weeds and more.
For timely updates throughout the season the CORN Newsletter can be
delivered right to your inbox. Visit corn.osu.edu/ for more information. If you are
interested in a little on-farm research and have some wheat, a sprayer,
combine and yield monitor or weigh wagon give me a call. I have one
spot open for a research project with Dr. Pierce Paul that carries with
it many benefits. For more information contact Justin Petrosino, OSU
Extension Darke County at (937) 548-5215 or petrosino.3@osu.edu.
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