Response to Fungicide Scores
Here in SE Iowa, we are in the most fungal-intensive area in the corn belt. Among the amount of inoculum, warm temperatures, and high humidity, our climate makes for an ideal environment for high fungal pressure.
Every hybrid is tested for most of the diseases we will be faced with in Iowa. The fungi tolerance that most hybrids are tested for in corn are gray leaf spot (GLS), northern corn leaf blight (NCLB), common rust, and southern rust; there are many more that are just now starting to be tested (such as tar spot complex) as they arise in the corn belt. The tests administered by the seed companies will generally have a score from 1-9, or they will use a good-very good-excellent scoring system as a way of classifying the hybrid’s response. While the number system seems more intuitive than a subjective “bucket” rating system with fewer classifications, keep in mind that for some companies a score of 9 indicates the best possible performance, and for others, a 1 indicates the best resistance, so be sure you know which you are looking at. While it is obviously beneficial to choose a hybrid that includes some level of resistance on its own, this alone is not enough to counteract the fungal pressure in our region.
Some companies take their rating system a step further by looking at the response to fungicide application, not just the plant’s innate resistance. This score is far more telling even though it has fewer categories: generally high, medium, and low response. This score indicates the effect that application of any fungicide is likely to have on each individual hybrid. While maximizing yield is always the goal, making the most informed decision on directing inputs to maximize productivity and profitability is the end game.
Ask yourself these questions:
- If the application of an additional chemical is not going to positively impact yields come harvest, is it worth the cost and time required to do so?
- If the seed you’ve selected has a positive fungicide response, why would you not use a fungicide?
A few years ago at an economics training, I was asked the question, “What is your most profitable bushel?” Is it the first one? Is it one of the first 50? The first 150? Or is it the last one? If a field averages 235 or 236, isn’t that last bushel the most profitable you harvest? If so, why would you not consider doing anything you can to add to that last bushel or two or twenty?
Have a conversation with your seed provider about how the hybrids you purchased react to fungicide to see if an application might pay on a particular hybrid. Odds are you will benefit from adding fungicide to those acres.