Tar Spot Showing Early this Year: a Note on Diagnosis

Jul 13, 2021

By Pierce Paul

I have so far only received one confirmed report of Tar Spot in the state, but the fact that the disease has been reported in a few neighboring states has some stakeholders asking questions about diagnosis and management. Tar Spot is a relatively easy disease to diagnose. As the name suggests, it usually shows up as raised, black spots, primarily on the leaf blast. The size of the spots may vary, but they all have a very similar appearance – raised, circular-to-irregularly shaped, black spots. However, is you do have trouble with diagnosis, please feel free to send me images and samples (1680 Madison Ave, Wooster, OH 44691).

This is the earliest we have seen Tar Spot in the state since it was first reported in 2018. Results from studies out west suggest that yield losses due to Tar Spot tends to be highest when it develops and spreads before tasseling (VT) on susceptible hybrids. Warm, wet, and humid conditions seem to favor the development and spread of Tar Spot, so keep your eyes on the weather, and watch the progress of the disease. If it continues to spread, a fungicide application may be warranted, but efficacy of fungicides against Tar Spot is still being investigated.

Source : osu.edu

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.