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Agronomist says tar spot is starting to show up in NE Iowa

A DEKALB technical agronomist, based in northeast Iowa, says tar spot has been slow to develop in her area, but conditions are changing.

Nicole Stecklein says farmers have been proactive with their fungicide treatments, but protections are starting to wear out.  “While we had those cool wet environmental conditions, you know, we were having those spores in the lower canopy get up on that upper canopy and it was starting to spread,” she says.

She tells Brownfield tar spot is an opportunistic disease.  “When we start to get to about half milk line and we start getting the senescence of the lower canopy naturally, that’s when we start seeing that tar spot really taking off and turning the brown,” she says.  “It’s when it’s really going to start accelerating the senescence of that plant.”

Stecklein says as harvest gets closer, growers will need to scout fields – especially if tar spot was an issue during the growing season.  “What we’ll really need to keep an eye on is stalk quality,” she says.  “And if we’re going to have any accelerated cannibalization and possibly sustainability concerns later on.”

Stecklein says growers should make note of fields where tar spot was an issue as they start to finalize decisions for the 2023 growing season.