Q: WHEN IS THE BEST TIME TO SCOUT FOR DISEASE IN CORN? HOW ABOUT IN SOYBEANS?

A: SCOUTING DOESN’T WORK WHEN IT COMES TO FUNGICIDES. I know it seems strange for an agronomist to tell you that scouting isn’t important, but that’s absolutely the case here. By the time you see a disease in your crop, you’re too late. Yield is already lost. That’s the frustrating thing with fungicides. You have to pull the trigger before you know whether or not it will pay. Personally, I like dealing with weeds and insects better because I can see them, spray them, and then watch them die. With fungicide, you spray it, and then you just watch your crop continue to look good. It’s not as satisfying… until harvest. If you ever leave check strips, which we often do, you will then see the difference with the combine.

WHEN DECIDING WHETHER OR NOT TO USE A FUNGICIDE, I ENCOURAGE YOU TO LOOK AT:

1. WEATHER. More rain means more disease.
2. CROP VALUE. High yield or a high price makes fungicide more likely to pay than low yield and a low price, and…
3. COST OF THE TREATMENT. If you are already spraying a herbicide or insecticide and you don’t have to pay for an extra trip across the field when you add a fungicide, that dramatically lowers your net cost. There are also super-cheap ($2) options all the way up to fantastic products that cost $20 or more so you can switch products based on your chance for ROI.

Q: HOW DO YOU PICK WHICH FUNGICIDE TO USE?

A: SPRAYING ANYTHING IS ALMOST ALWAYS BETTER THAN NOTHING, ESPECIALLY WHEN YOU HAVE 2 OR 3 MODES OF ACTION. If the choices are exhausting because there are so many different products available, just pick something. Fungicides today are great, and we usually see decent yield gains when products are used correctly. The more modes of action you use, the more broad-spectrum your control and the less chance you’ll have for resistance concerns. However, like I said above, if you need to get by cheap, there are options for you; and if you are worried about an impending disaster, there are amazing fungicides that cost more money.

Q: YOU SAY “JUST PICK SOMETHING”, BUT HOW ABOUT SCLEROTINIA WHITE MOLD IN SOYBEANS? WHAT IF I WANT NO GREEN STEMS IN SOYBEANS? HOW ABOUT TAR SPOT AND SOUTHERN RUST IN CORN?

A: Just to be clear, when I say “just pick something,” I simply mean the yield difference between spraying a fungicide vs. not is usually bigger than the yield difference between spraying the best fungicide and another fungicide that is also labeled to control that disease. You still have to be choosy in terms of the fungicide you use if you want to maximize yield gain.

1. WHITE MOLD. You will need more than just fungicide to completely stop white mold, but our advice is to use Cobra at 6 ounces right before flowering. Then, follow with Endura at 11 ounces 3 weeks later. Spray another product with white mold activity 3 weeks after that – and if you really want to stop white mold, spray again 3 weeks later. Yes, it’s costly, but on our farm, we only spot spray for white mold where we’ve had issues in the past, so treating 10% to 20% of our acres keeps the total cost down.
2. NO GREEN STEMS. I can’t guarantee you no green stems, but you’ll likely see a dramatic difference if you just cut the strobilurin chemistry. Our favorite “no strob” fungicide is Lucento, which does have 2 modes of action and is extremely effective on most soybean diseases.
3. TAR SPOT OR SOUTHERN RUST. BASF will talk about the long-lasting control of Veltyma. FMC will say almost the same thing about Adastrio. While these products may be slightly better and last a little longer, there are many other fungicides like Delaro Complete that have shown good effectiveness on these diseases. The trick to stopping both tar spot and southern rust is often to spray a second shot late in the season. For example, in each of the last two years we’ve seen farmers in Nebraska who have sprayed in mid-August achieving massive gains, as much as 40 bushels per acre. It doesn’t always work this way, but if you have a bad disease year, southern rust and tar spot can be relentless.

Q: IN CORN, SHOULD I BE WAITING UNTIL AFTER TASSEL TO SPRAY A FUNGICIDE?

A: NOT NECESSARILY. We like Xyway at planting time. Over the years, we have seen good results spraying $5 to $7 worth of fungicide with a herbicide around V4-V6. BASF has said “5 feet, time to treat” for the past couple of years, and we have found that once the ear leaf on corn is out, protecting that is worth a lot; and spraying pre-tassel can pay pretty well. Ultimately, it matters most when disease shows up, and the problem is you don’t know exactly when that is going to happen. With diseases that must blow up each summer from the south – rust, for example – you can follow scouting reports from areas south of you to see if an outbreak appears likely.

Q: WHAT CAN I DO TO MAKE MY FUNGICIDE WORK BETTER?

A: SPRAY BEFORE YOU SEE THE DISEASE. Use 20 gallons of water per acre. Spray with relatively high pressure and smaller spray droplets when the wind is fairly calm. Spray when the weather is a little cooler rather than in the heat of the day mid-summer. Lower the water pH to below 6 with something like Water-Rite. Add fulvic acid (we use Ful-Four or Nutex EDA) to help get fungicides into the plant faster and more efficiently. Use a “fungicide-friendly” surfactant. For example, adding a surfactant is inexpensive and usually improves fungicide uptake and performance, but when spraying corn pre-tassel you need an APE/NPE-free adjuvant so you don’t cause arrested ear syndrome.

Q: ARE FUNGICIDE PRICES COMING DOWN NOW THAT SOME OF THE BEST PRODUCTS ARE OFF-PATENT?

A: ABSOLUTELY. In the last 20 years, my list of amazing fungicides has included Headline, Endura, and Proline. These are now all much lower in cost. Fungicide prices are down this year, and I expect them to go even lower in the future. That means a better chance for a great return on investment, and it also means if you’ve been skipping the fungicide application because it’s “too expensive,” it may be time to re-think that strategy, especially as yield potential goes up and disease issues continue to get worse.