Southern Spotlight: Fungicide at Tassel

James Banahan

James Banahan

Fungicide at V5 is a seriously good decision.

But what’s that you say?  Your plants are way past V5?  You didn’t do a fungicide then?


You, fortunate grower, are in luck.  Fungicide at V5 is a good idea, but if that ship has sailed, fungicide at tassel time has many benefits as well.

Applying fungicide at tassel also produces one of the most important benefits of application at V5: reduction in nighttime respiration.  Nighttime respiration is real and happening in your field.  And it is costing you yield as your corn plants burn their valuable sugars rather than pack them into kernels.  Fungicide reduces this stress reaction in corn plants by facilitating stomatal activity.  Happy stomata = less stress = fatter kernels = increased yield = happy dances and higher profits for you.

Though this benefit alone may justify the investment of a fungicide at tassel, it comes with many other important benefits as well, including a reduction in disease pressure and in lodging.

Fungus causes many problems for our crops including Gray Leaf Spot, Southern Rust, and Common Rust.  Gray eaf spot overwinters in corn stubble, whereas southern and common rust are usually blown in.  With fungi that overwinter and fungi that hitch a ride on the breeze, all fields are susceptible to infection and the resulting yield losses.  A fungicide at tassel time will address such issues, whether you’ve repeated corn in a field and fear gray spot or cycled and worry about what our windy year has carried in.

Attention to the prevention of a fungal infection among your corn plants is especially vital this year.  Fungi favor wet, warm, and dark conditions, much like you find under the corn canopy right now as we sweat through hot days and as even unirrigated fields find themselves near saturation.

Our wet growing season has its benefits, of course.  With water in good supply, we have the possibility of high yields.  Our plants are aiming for this—they’ve got the water they want, so they are growing.  And growing.  And growing.  Which is awesome.  If our plants’ demands for nutrients outstrip what is available in the soil however, they’ll begin to pull it from their own tissues.  Which isn’t awesome.

Essentially, our plants are probably on course to outgrow the nutrient plans that we set forth before the season began.  Without enough nutrients in the soil, corn plants will pull nutrients from the tissues furthest away from the ears they are working so hard to fill—meaning that our plants will begin to cannibalize their own stalks.  This, as you might expect, weakens the stalk which in turn leads to lodging at harvest.  A fungicide addresses this issue by strengthening lignin, the stringy part of the plant, thus helping the plants to continue to stand even as they pull nutrients and weaken their stalks.IMG_5734

The reduction in nighttime respiration is on its own enough to justify the expense of a fungicide at tassel—so is the reduction in lodging.  That one product produces both benefits makes it a very good product indeed.  Last week, I wrote that leaving just three kernels per ear of corn in your field at harvest amounted to leaving an entire bushel per acre in the field.  If you’ve experienced lodging before, you probably know that you end up leaving a whole lot more than that.

Assume, for the sake of this point, that 20% of your stalks lodge.  If you’re planting about 25,000 seeds, that means about 5,000 plants would be affected.  Even if you were able to salvage half of those ears, you would still be leaving a whopping 14 bushels per acre in your field.  At $4 per bushel, that’s a $57 per acre loss.

Yield loss like I’m talking about here is a compounding issue.  Without application of a fungicide, you originally suffer potential yield loss as your stressed plants burn precious sugars.  The next yield loss comes at the hands of fungi.  The final blow comes from stalk lodging and the alarming amount of yield it causes you to leave in your fields.  Because corn at tassel is a good size, it requires more product and aerial application which yes, means that fungicide application at tassel costs more than application at V5.  However, given the compounding yield losses probable without an application, the $25 investment per acre is worth it.  It’s an investment that you’ll easily make back, perhaps in double or more.