Mid-season diseases – what are we watching out for?

I’ve scouted a number of fields and driven by many acres in the past two weeks and the crop looks great.  A bit behind in some areas, but soybeans can compensate fairly well.  With that comes the question what do we need to watch out for next.

  1. Frogeye leaf spot– particularly in those fields where it was present at high levels last year and the field is in soybean this year.  I will assume that this practice was done due to the late planting date and not a continuous soybean practice.  In these fields there is a higher probability that frogeye leaf spot will start early.  If you do find spots, gray lesions with purple borders, look on the underside to see if there are whiskers (spores) on the bottom of the lesion.
  2. Lots of noise about soybean rust this year.  This is the first year that levels are high in the very deep south:  Florida, Alabama, Mississippi, and Louisiana.  The good news is that the hot, dry weather forecast for most of this summer should keep it in check.  In the past, from the sentinel plot surveys we have noted that once a pustule is found (1/100 leaves) – that this gives a 3 week notice.  Unlike our southern producers who have spore deposits every day – Ohio and northern states have to wait for a large wet weather event to bring the inoculum in.  It must then multiply in the field (9 to 10 days from inoculation to sporulation) and build-up with the field.  To date no weather event has occurred and we will continue to monitor the situation especially for those late planted soybeans.
  3. Brown spot – where did it go?  I have been very surprised at how clean the lower leaves and unifoliates are this year, even in no-till fields.  This is really an indication of how dry it was for the time period following planting in many areas of the state.  We will see how it looks next week after several rain events.
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About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.