Tar spot

The 2022 yield loss from diseases affecting the Kansas corn crop was recently estimated at somewhere around 10 percent. Four percent was attributed to nematode losses, and another three percent from stalk rots. The other three percent is blamed on a combination of ear rot diseases, and the ones we spend most of our time worrying about: foliar diseases.

Tar spot was one of those foliar diseases in 2022. First reported in the Midwest in 2015, the disease has spread through the Corn Belt, reaching Kansas in mid-September, affecting fields in Nemaha, Doniphan, Brown, Atchison, Jackson and Jefferson Counties. Its contribution to yield loss was likely minimal, affecting most fields too late in the season to result in damage.

Because of its ability to survive on residue, however, it could be a disease to watch for in 2023. Later infections may not be a big deal, but if heavy tar spot levels show up early in the season, susceptible hybrids could be significantly affected. Want more background on tar spot, as well as some of our more common corn foliar diseases (Southern Rust and Gray Leaf Spot come to mind)? If so, hold Thursday, Feb. 15. That’s the date for two area Corn/Soybean Disease Management meetings.

More information will be available in this space next week, or check out a flyer on the events page of the Meadowlark Extension District at https://www.meadowlark.k-state.edu/events/.

Truth or Myth: Coffee Grounds to Lower pH

Most of our commonly grown landscape plants prefer pH levels in the six to seven range. There are some, however, that will do their best only in a more acidic soil pH: azaleas, holly, butterfly bush and blue hydrangeas are examples. For those plants, sometimes soil pH needs lowered for best results.

Correction of soil pH isn’t a rapid process. It requires a soil test to determine actual soil pH level. When pH is determined, an application rate of elemental sulfur can be calculated. Even then, it’s likely to take three to six months to lower pH (in short, plan ahead) appropriately.

Some gardeners promote using used coffee grounds to drop pH. Unfortunately, used coffee grounds have essentially a neutral pH. Fresh, non-percolated grounds do have some level of acidity, but elemental sulfur is probably still a better bargain over applying fresh coffee grounds to landscape beds.

Spent coffee grounds aren’t useless, however. They contain carbon, nitrogen and other compounds that can provide food for soil organisms. Once they break down, they can increase organic matter and help build soil structure.

Coffee grounds aren’t all bad…Just don’t plan on them lowering pH levels. Elemental sulfur is a better option for that.

David Hallauer55 Posts

David Hallauer is the Meadowlark Extension District agent in the areas of horticulture and crops and soils.


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