Tar spot not a problem yet in Wisconsin

A crop disease specialist says so far, Wisconsin farmers have not had a problem with tar spot in corn.

Dr. Damon Smith with the University of Wisconsin Madison tells Brownfield with several other states reporting signs of tar spot, he’s been looking for it. “We haven’t seen it yet. That doesn’t mean that it potentially isn’t out there, but we’re not finding it, so as of right now, that’s a good thing. We definitely don’t want it to show up this early.”

Smith says when tar spot comes in this early and gets moving, it reduces yields.  He says most farmers should not rush out and spray fungicides yet. “V-6 growth stage with six emerged leaves, those leaves are not going to be there at the end of the season or even mid-season, and so protecting those leaves at this point with a fungicide doesn’t make a lot of sense from a biology standpoint or an economic standpoint.”

Smith says the fungicide is most effective during the early tassel to early milk growth stages.

He says many farmers have asked why some states are seeing tar spot and Wisconsin hasn’t found any yet. “We didn’t generally have a strong epidemic in the state last year, and I think some of that is residential innoculum, if you will, from last season that’s sort of moving those epidemics along.”

Smith says farmers will need to keep scouting for diseases like tar spot since the moist conditions make it ideal for new outbreaks.

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