By Blake Jackson
As the growing season advances, deciding whether to apply fungicides remains one of the most challenging management choices for Midwest farmers.
According to Damon L. Smith, Extension Field Crops Pathologist at University of Wisconsin-Madison, rising input costs, aggressive product marketing, and varying opinions on fungicide use make it difficult to determine the best time to spray while protecting farm profitability.
Many growers have traditionally relied on crop growth stages or calendar dates when planning fungicide applications. However, these methods do not always provide the best return on investment because disease development depends on several factors.
Plant diseases occur only when a susceptible crop, a disease-causing pathogen, and favorable environmental conditions exist at the same time.
To improve decision-making, farmers can use science-based forecasting tools such as the free Crop Protection Network (CPN) Crop Risk Tool.
The platform combines weather data with disease prediction models to estimate the likelihood of disease development for specific locations. These forecasts help producers determine whether to intensify field scouting or consider a fungicide application.
The way forecasting tools are used depends on the biology of the disease. White mold in soybeans is a monocyclic disease, meaning it generally experiences only one major infection cycle each season. Because preventive action must be taken before infection occurs, risk forecasts can help determine whether fungicide applications are justified during flowering, particularly in fields with a history of white mold.
Tar spot in corn behaves differently because it is a polycyclic disease capable of producing multiple infection cycles during the season. In this case, disease forecasts are most effective for identifying fields that require closer scouting before making spray decisions.
Smith emphasizes that combining disease forecasts with regular field observations and professional agronomic advice can improve fungicide timing and economic returns.
Smith also encourages growers to avoid unnecessary fungicide applications, as excessive spraying increases production costs and contributes to fungicide resistance. Careful, data-driven management helps preserve the effectiveness of available fungicides while supporting long-term crop health and profitability.
Photo Credit: gettyimages-oticki
Categories: Wisconsin, Crops