Corn Fungicide Planning

It may seem a little early to be thinking about fungicides in corn with the slow spring we have had and a lot of planting just getting underway, but now is the time to start planning for summer fungicide applications. Most corn hybrids have a response to fungicide score, or RTF. While preparing for planting, it is important to remember which hybrids are planted in each field so those acres with high RTF scores can be targeted for treatment with a quality fungicide. Fields with moderate to low RTF scores should still be scouted throughout the summer for disease pressure, with treatment decisions based on field findings and the movement of tar spot.

Tar spot is still relatively new to our area, only becoming more common over the last three to four years. Most fields across the trade territory I work in have shown late season tar spot symptoms during the last three growing seasons. Fortunately, the disease arrived late enough that yield loss was limited in most cases. We may not be as fortunate in 2026. Tar spot is a disease we are still learning to manage, and it will likely reshape how many recommendations are made for fungicide applications on corn acres going forward.

Last year, many areas across the state also experienced a widespread outbreak of southern rust. Fields that did not receive fungicide treatments saw losses of 60 bushels per acre or more in some situations. In many cases, the disease spread rapidly across fields, making rescue treatments difficult even with active scouting. Between the southern rust issues last season and the continued spread of tar spot, many growers should consider fungicide applications as a planned management pass rather than a reactionary treatment after disease is already established.

Now is a good time to sit down with your local agronomist and review the RTF scores of the hybrids you plan to plant. Building a fungicide strategy ahead of time can help protect yield potential and make in-season decisions easier when disease pressure begins to increase. When making fungicide applications, it may also be a good opportunity to include foliar nitrogen or micronutrients, especially boron, to maximize the value of the trip across the field.