By Brian Hefty

Fungicides drive me crazy because I have to spray them before I even see a problem, and there’s no guarantee they are going to pay.  And “plant health”?  What’s plant health?

All you should care about is, “Does fungicide give me a good return on investment?”  Here are the 7 most likely situations where fungicide should pay off well for you on your farm.  Let me preface that by saying that if you can double your money or at least get a 50% ROI, that’s really good.  In yield, though, that may only mean a 2 bushel yield gain in soybeans or a 5 bushel gain in corn.  That won’t even show up on your yield map unless you look really closely.  I’m just trying to say that while the yield gain may not be high, that’s not the important thing.  Keep your focus on net dollars returned to your operation.  With that, here’s my list of when fungicides are most likely to pay.

  1. BUGS.  If you have bugs, you’ll get a greater ROI.  Every time an insect (like soybean aphids, corn borers, bean leaf beetles, corn leaf aphids, grasshoppers, cutworms, rootworms, etc.) feeds on your plant, it opens it up for diseases to get in.  It’s the same thing when damage occurs from hail, wind, nematodes, or equipment.  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.
  2. SUSCEPTIBLE VARIETIES.  If you have susceptible varieties, fungicide is more likely to pay.  Everyone always wants the racehorse hybrids or varieties.  That’s fine, but what you gain in yield potential, you often give up in defensive traits.  Talk to your seed provider about this, but keep in mind that when new seed lines come on the market each year, we don’t have the benefit of experience like we used to.  If a corn or soybean that you really like is only a year or two old, how much does your local seed dealer or even the seed company really know about it?  My point is simply to be a little on the conservative side and assume company disease tolerance ratings are usually too favorable.
  3. WET WEATHER.  Fungicides are more likely to pay when the temperature is moderate and the weather is damp.  You don’t need lots of rain, but clouds, mist, and wet soils typically allow diseases to thrive.  Sunlight and heat are the enemies of most diseases.  In a year like last year, when drought was common in many areas, diseases were not nearly as big an issue as normal.
  4. DISEASE HISTORY.  If you have a history of disease, you are more likely to have a problem this year.  Many of the diseases that ravage corn and soybean fields stay in the ground for years.  The longer you rotate away from a particular crop, the less likely that same old disease will show up again in the same field.  If you are raising the same crop year after year, your chance for disease issues goes up.
  5. NARROW ROWS.  For years farmers have discussed planting wider rows to allow more air to move through, reducing disease pressure.  The problem is wider rows could lead to lower yields.  If you don’t want to give up your narrow rows, consider using a fungicide.
  6. WEEDS.  I’ve never seen any studies on this, so this is just based on my experience as an agronomist.  When a crop is struggling hard to compete against weeds, it is under stress; and we all know that plants under stress are more likely to get hit by disease than plants that have no stress.  If you had issues keeping your field weed-free this year, I personally believe fungicide is more likely to pay for you.
  7. HIGH YIELD.  If you are hoping to gain 5% in yield with fungicide use, it only makes sense that 5% on a high yield makes you more money than 5% on a low yield.  The more appropriate way to look at this, in my opinion, is if you have removed the yield-limiting factors to get you up to a high yield, odds are greater that the next limiting factor could be a disease.

Real quickly, here’s what I would suggest you at least try on your farm this year:

  • CORN – Spray at V6-V7 and again at full tassel, especially if you have at least 3 or 4 of the above conditions.
  • SOYBEANS – Spray at R2 (full flower) to R3 (first pod).

Compared to corn fungicide use, we have seen the soybean applications pay off more consistently in our area (Dakotas/Minnesota).  The yield gains have been modest, but the ROI has been good.  In areas where gray leaf spot is present (Iowa, southern MN, etc.), the corn treatments have been big yield-gainers.

Finally, when it comes to selecting the right fungicide, you have a lot of choices, so it’s probably best to talk to your agronomist.  We are switching some of our straight Headline work to Priaxor (pre-mix of Headline & Xemium) to get more broad-spectrum control and help reduce potential resistance issues.  Domark is a good one for white mold.  Evito is a good strobilurin.  Stratego YLD and Quilt Xcel each have 2 modes of action.  More important than the product you use is often the timing of when you spray and the spray coverage.  Fungicides move poorly in the plant, and fungicides can’t recover yield you’ve already lost if you spray too late, so do your best to properly manage your fungicide treatments this year.