Tar spot is ever-expanding across the Corn Belt, and infestation reports are mostly coming in from fields planted to continuous corn and/or irrigated corn. While the risk of economic losses to the disease is quite real, good soil health and supplementary plant nutrition can go a long way to keeping the disease damage to a minimum.

A standard preventative fungicide program will typically limit tar spot disease and can be mixed Ag Spectrum’s foliar nutrition program of PT-21®/Score®/GroZyme®. Be sure to select a product that is labeled for tar spot control. Keep the total spray volume to less than 10 gal/ac to ensure the proper balance between coverage and efficient absorption. And remember, that even when using Indicate 5® and Insure® as spray water treatments, it is always wise to check mixing compatibility with a jar test before proceeding to the field to spray.

Before applying fungicide it’s important to scout fields and properly diagnose the disease. Check your corn fields between V12 and R2. If tar spot symptoms are clearly visible on the ear leaf or just below during that period, then be sure to spray a fungicide mix labeled for tar spot control. Currently, there are several products on the market that include both triazole and strobilurin active ingredients, and all have similar levels of efficacy.

Remember that complete implementation of the Maximum Farming System goes a long way to minimizing crop disease by naturally supporting crop health. Crop stress is a primary driver of crop disease development, and a complete nutrient management system that mitigates stresses throughout the growing season is necessary. By properly implementing the Maximum Farming System, the risk of economic losses due to crop diseases is significantly reduced.

-submitted by Brian Gardener, Ph.D., Technical Director