This has been a very challenging year for soybeans in Mississippi. Although much of the crop is early, many producers had to deal with waterlogged soils and flooding in early July.
In some areas, we were not able to get back into fields to complete planting until the week of July 12. Although a small portion of the crop overall, it is large for those producers facing the extremes.
I have received numerous calls regarding foliar fungicides. Deciding whether or not to use them is somewhat a guessing game. In most situations, several options usually will work. No one option, however, is the total answer.
We have made and will continue to make high yields without fungicides (some years). However, the use of fungicides and late-season insect management will be essential to consistently achieving high yields.
The early planting system is an avoidance mechanism for many foliar diseases. The system has a greater risk of seed deterioration than of losses from foliar diseases. Sure, we have seen some frogeye leaf spot and late-season cercospora, but an application decision is a little harder when you only have two weeks to go.
When it finally quit raining, some acreage was only one to three weeks from being done. We did not need much protection there, so it became essential to look at future weather. We stayed the course and concentrated on seed quality because so much of the state's crop was nearing complete seed fill.
On mid-April and later plantings, an in-season application would be more beneficial. Once again, we had to decide what we needed to control.
Dry weather will slow disease progression greatly. Admittedly, the three weeks of rain in June set us up for greater disease pressure, but the weather that followed played a major role.
I believe in the preventive approach to disease control, but even with that you have to decide what you need the most protection from because no one option offers total control.
I think many producers are making the decision more difficult than it should be. I will continue trying to simplify the process, but it remains somewhat of a guessing game. You must answer questions such as, “How much of the growing season is left?” and “What are you most concerned about controlling?”
Planting date also complicates the decision. We know early planting dates are beneficial, but the big questions were: How much protection do I need? How much longer until complete seed fill?
Many fungicide applications were insurance shots because we did not need as much protection on a Group 4 or Group 5 variety planted prior to mid-April as we did on those planted in May.
We have a certain amount of disease pressure this year due to the three weeks of rain in June. Nothing we could have done would have changed that.
Regardless of what you have heard, I am not making blanket applications of fungicides. When making a decision I take into account acreage, planned delivery of the crop, variety, planting date, cropping history, and weather. We are still on track with our earlier plans, and hotter, drier weather since early July has helped solidify that decision.
Alan Blaine is the Mississippi Extension soybean specialist. e-mail: firstname.lastname@example.org