By Brian Hefty
If you raise soybeans, you should be spraying at least some of your acres at R2 (full flower) to R3 (first pod) with a foliar fungicide like Headline, Evito, Quilt, Stratego YLD, or Domark.
Brown spot, cercospora, downy mildew, rust, frogeye leaf spot, rhizoctonia aerial blight, pod & stem blight, alternaria leaf spot, anthracnose, powdery mildew, white mold, and other diseases may infect your soybean crop this year. Unfortunately, you can’t wait to see a bunch of disease issues in your field before you treat. Well, you can, but you will have already given up significant yield. Fungicides are PREVENTATIVE. Even fungicides that claim “curative” properties can’t recover the yield you’ve already lost when a disease is allowed to damage your crop, even for a short time.
Over the last few years, we have studied fungicide applications at great lengths in several crops. Here’s what we’ve learned in soybeans.
- Don’t expect huge yield gains, but it can certainly happen. Look at the average over a period of time to determine the worth of fungicides on your farm. Our top, in-field yield gain has been 17 bushels per acre that we have documented in large side-by-side trials on our farm. By the way, that was with a half rate of Headline (3 oz per acre). Our average has been 2 to 3 bushels per acre when using the half rate of various fungicides. That doesn’t sound like much, but when you only spend $6 and get $20 to $40 back (depending on the soybean price), that’s a great ROI, especially when we’re out there spraying already for insects.
- If you have bugs, you’ll get a greater ROI. Every time an insect (like soybean aphids, bean leaf beetles, grasshoppers, cutworms, etc.) feeds on your plant, it opens it up for diseases to get in. Think about it like you would for human beings. If you get a few cuts on your arm, what’s the first thing you do? You sterilize the wound (at least I hope you do), so infection doesn’t get in. The way you sterilize all those wounds in your soybean crop, in effect, is by spraying a fungicide.
- If you have white mold, use the full rate of Domark twice, at R1 (first flower) and again at R3 (first pod). Also, consider using Cobra herbicide, as that will thin your canopy, allowing more air to get through and reduce your incidence of white mold.
- You may have green stems in the fall. If you don’t like that, use Domark. If you are using Headline, Evito, Quilt, or Stratego YLD expect a few (or more) green stems. If you get a hard frost, that will obviously take care of that, but keep in mind you are seeing green stems because your plants didn’t prematurely die. I like seeing green stems, because that typically means I get higher yields.
- Use high rates of fungicide if you are concerned about disease resistance, if you are in a wetter or more humid area, or if you’ve had disease issues in the past. Bumping the rate will cost you an extra $6 an acre or so, meaning you don’t have to gain much yield to justify the higher dose.
- If you don’t believe fungicides pay at least run some strip trials on your farm. That’s how we figured things out over a period of years on our farm and the farms of hundreds of others. Personally, I would spray a fungicide on soybeans if I raised beans anywhere in the U.S. I know it pays…not necessarily every year, but the average looks good. Also, if you are testing fungicides, don’t trust your yield monitor. Is your yield monitor really going to pick up 1.5 to 3 bushel differences? I doubt it. Weigh out your trials, and run several strips with and without fungicides for the best possible tests.