Weed and insect control is much different than disease control. You can see a weed or a bug and spray it, pull it, or otherwise eliminate it from your field. As long as you’re timely, you can generally do a pretty effective job.

With diseases on the other hand, once you see them they’ve already become established. At that point, you’re too late to stop the yield loss and often too late to stop the continued spread of the disease. For that reason, planning ahead is absolutely critical.

VARIETAL TOLERANCE

Much like how picking the right Bt hybrid or the best herbicide-tolerant trait that can help with weed control, there is a difference in varietal tolerance for SOME of the worst diseases, so be sure to visit with your seed dealer about that to give yourself the best chance. With tar spot specifically, there are some hybrids that tolerate it more than others, but nothing is great just yet.

PLANTING TIME FUNGICIDE

You will have seed treatment fungicide to help protect your seed and young seedling, but even the best three- to four-active-ingredient fungicidal seed treatments will not last long enough to stop mid- to late-season diseases. Consider Xyway this year. It’s the only fungicide you can use at planting that lasts most of the season. It’s labeled for gray leaf spot, northern corn leaf blight, and others. While not labeled for tar spot, I spoke with growers who used Xyway this year who saw less tar spot activity in those fields.

HERBICIDE TIMING

In the V4-V7 timing (four to seven leaf collars), most farmers use a half rate of fungicide to spray small corn plants. While disease control is normally not a big deal this early in the season in corn, improvements in overall plant health have been observed. Also, the cost is really low to do this if you tankmix the fungicide with your herbicide application.

PROTECT THE EAR LEAF

While early-season disease issues may not be a big deal, once the ear leaf is out, protecting it from disease is critical for achieving top yields. We’re seeing a growing trend of spraying before tassel. Just use an APE/NPE-free adjuvant like Precisive or Nutex EDA to make your fungicide work well without the risk of arrested ear development.

PROTECTION LASTS 2-3 WEEKS

Keep in mind that fungicide protection with foliar applications only works on the leaves and plant tissue you spray it directly on. That protection should last 2 to 3 weeks. If you have a tough disease like gray leaf spot or tar spot, you’ll need to plan another treatment 2 to 3 weeks after your first application to protect new leaves and extend your disease control.

USE MULTIPLE EFFECTIVE MODES OF ACTION OR (MOA)

Strobilurin fungicides like Quadris and Headline are great plant health products but aren’t great disease control options anymore due to resistance to this chemical family. Using combination products that contain SDHI and triazole family fungicides is a good idea. Lucento is a strong two-MOA product that fits that mold. Products with three MOA like Delaro Complete, Trivapro, and others work very well, too, but keep in mind that even though they are three-MOA fungicides, there are only two EFFECTIVE modes of action in there, since the strobilurin no longer stops most diseases.

RETURN ON INVESTMENT (ROI)

Work with your ag chemical retailer to learn more about rebates and the best prices for each of your fungicide choices. In the end, with corn prices strong, the ROI should still justify fungicide use and likely multiple applications if you have even moderate disease pressure in 2023. Just three to four bushels of corn per acre will cover even the premium-priced products! With many growers losing 50 bushels per acre or more to tar spot in 2021 and 2022, fungicide protection is often a slam dunk when timed properly.