By Darren Hefty
As a long-time agronomist, I’ve heard all kinds of crazy claims over the years. If the claims come from the sales and marketing department, I take them with a grain of salt. If those claims come from the research and development people, it’s generally a different story. When it comes to fungicides, there are a few statements that can easily be misleading and need to be understood:
#1 – “This fungicide has CURATIVE properties.”
We’re used to seeing a weed, spraying that weed, and killing the weed. Same goes for bugs. If you’ve got a bug problem, you scout for the bug, then spray it, and see its dead carcass laying there in the field so you know you got the job done and protected your crop. With fungicides, it’s a completely different story. ALL fungicides work much better when sprayed in advance of any disease on your plants. Once a disease is visible enough for you to see it, chances are it’s too far gone and you have already lost yield. Also, if the disease has already started to destroy leaf tissue, you can’t fix that. Can you stop a disease that’s just getting started? Maybe, but only if it’s truly JUST getting going (like a 1 to 3 percent infection).
#2 – “This Fungicide TRANSLOCATES Through the Plant.”
When you spray a foliar fungicide, don’t expect much movement. There are two transport systems in the plant. The phloem is one system which moves up and down bringing water and nutrients throughout the plant as needed. The xylem is the other and only moves up. Fungicides that actually get into the plant move in the xylem. If you spray a leaf, for example, and only spray a strip across the middle of the leaf, fungicide can move out towards the tip of the leaf but will not move back towards the stem.
#3 – “A HALF RATE of a Fungicide is All You Need.”
Brian and I say this all the time but there’s more to the story than just, “Can I use a half rate?” The real question is, WHEN can I do this and be successful? Where we most commonly recommend a half rate of a foliar fungicide is in crops that are very small and immature. For example, in wheat we often use a half rate of fungicide when spraying at herbicide timing. The wheat is only a few inches tall. Fungicide can only protect the plant when it lands and sticks on the leaf surface. What good does it do to spray the same rate you’d need on a waist high stand of wheat? The same is true in soybeans. Our soybeans are often only about a foot tall and are in 30-inch rows when we spray them in the early reproductive stages. There’s no point using the same rate we’d use later on when the beans are fully canopied and have 5 to 10 times the plant mass. The other thing to keep in mind is that we farm in a fairly arid climate. If we were in Mississippi on a wet year with lots of humidity and heat, etc., we’d plan on using a stronger rate or even multiple applications.
So What’s the Plan to Make Fungicides Work?
- Use multiple modes of action to prevent resistance
- Use plenty of water and spray pressure to cover the plant from top to bottom
- Use flat fan nozzles or alternative nozzles that create small droplets to ensure excellent coverage
- Spray early before disease gets started