One of the main things we have learned about growing soybeans through the years is that they respond well to midseason fungicide applications. This response varies with several factors including weather, variety, maturity group, current disease information, and field history.
Diseases have changed through the years, making the choice of product important, and timing of applications can have a lot of influence on effectiveness and economic return to investment.
As we reached the end of June many of the soybeans in this area were reaching the growth stages that have been shown to be the best for making yield enhancement applications.
When we started making these applications on a fairly regular basis about 20 years ago, many applications were made at the R2 stage when blooms can be found within the top four nodes of the plant. More recent experience has suggested that the best time to make these applications may be as late as R4 or R5 when tiny beans can be found inside the pods near the top of the plant.
This means that we have a fairly wide window of time during which yield enhancement applications can be made with good expectation that the response will be positive. This fact helps a lot of growers get their fields treated in the most effective ways, maximizing the effectiveness of products by using higher volumes of water. Coverage of plants is important for best results.
Every year we go through the process of deciding whether to make the yield enhancement application. There are very few things that I consider as standard practice in crops, but the use of fungicides for yield enhancement in soybeans has for me become standard.
I still catch myself trying to rationalize away from this application, but the few times I have allowed my weaker nature to prevail, I have regretted it later.
Yield response is never the same from one year to the next with results depending upon some of the same factors mentioned above, with weather and variety being the primary issues. Ironically, some of the highest-yielding varieties are also some of the most disease susceptible, particularly in the case of frogeye leafspot.
Varietal response may also play a role with other diseases as well, but I will leave that to the pathologists to debate that subject. I am satisfied with my own conclusion that when it’s time to make the application just go on and do it.
Paying for application
A further issue, particularly now when prices are lower, is that it will take the return from more of the crop to pay for the application. And this is the way I normally think about it — when soybeans are $10 to $12 per bushel only 1 bushel will just about cover the cost of the material, but this year almost 2 bushels will be needed to pay for it.
However if you think about it carefully you will realize that in a year like this the application is even more important since we need to produce every bushel possible. The application also helps overcome some of the difficult field conditions we have experienced up to now, so there again the justification is apparent.
I’m not going to get into the issue of which products to use since this should be left to someone who can make on-the-spot decisions based on variety and disease pressure.
Insecticides can also be included, as well as Dimilin to head off later development of many of the most potentially damaging pests. Several of us with Extension can help with this as well as qualified consultants and company field reps.
The MG4 varieties are about ready now, and the MG5s will be following along in a couple of weeks. Wheat-beans and late-planted fields will come last. Common sense is part of the equation as well, such as a field that has been drowned out or destroyed by wildlife. Otherwise I suggest that the application is justified.