by David Bennett, Delta Farm Press
Target spot has struck many Mid-South soybean fields this growing season leading to decreased yields. Now on the back end of soybean harvest, growers are asking questions about the fungal disease.
To get some answers, Delta Farm Press spoke with Tom Allen, Mississippi State University plant pathologist, in mid-October. Among Allen’s comments:
On potential varietal differences…
“One thing I’ll say is, at this point, we have some decent varietal observations on target spot, but not hard and fast data regarding the yield losses associated with this particular disease.
“I’d say for the last two to three years from looking at the soybean OVTs in Mississippi, I’ve been able to rate diseases that include target spot. The hard part about speaking on some of the observations is rating for target spot can be a little bit more difficult than a disease such as frogeye.
“Target spot is normally observed in the lower to middle part of canopy. In general, target spot doesn’t normally move into the upper canopy and certainly isn’t primarily observed in the upper canopy like frogeye leafspot. That presents a huge issue when studying target spot – you have to part the canopy and look to see how high the disease has moved in the canopy. Any of the ratings I’ve done provide decent ideas about where target spot will be in the canopy (bottom, middle, top) based on particular varieties.
“Now, fast-forward to this year where we’ve been able to observe specific varieties that appear to be extremely susceptible to target spot. The problem is everyone seems to have a different list of varieties and some of those have tended to be on the list of some of our better yielding varieties based on yield potential over the past several years.’