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Pro and custom applicators understand that their methods play a big part in how successful and effective they are at making spray applications. And, that a successful spray application must also use your time, chemical, and water resources efficiently, and limit any environmental impact.
So what is the right way to apply a pesticide or herbicide? To answer the question properly, you need to look at four factors:
Canopy
Water volume
Target type and droplet behavior
Mode of action
To start, look at the crop canopy to be sprayed. If it’s an early season spray into a seedling crop, then the canopy won’t provide much of a barrier. Think about using a lower water volume. Droplet size will only depend on the crop and the mode of action.
If it’s a later season application into the bottom of a maturing canopy, the foliage may intercept the spray before it reaches the target area. You might need more water, and droplet size may become more critical for getting the spray to its destination. Dense canopies can be a significant challenge. Lower canopies usually benefit from finer sprays because small droplets can better turn corners around foliage.
Regardless of canopy, there are a number of application possibilities that will depend on water volume and spray quality combination. It’s simple math: Assuming some constant amount of coverage on each leaf, more layers of foliage will require more water. Using less water volume will make it necessary to use finer sprays to keep droplet numbers constant. More water will allow coarser sprays.
This decision has implications for drift, and by extension, affects the number of hours you can spray in a day. More drift tolerance means better application timing and overall productivity.
Whatever spray you use, the target plant and/or pest needs to intercept, collect, and retain the spray droplet. Target leaves may be vertical or horizontal, large or small. Their waxy surface may be easy-to-wet or difficult-to-wet.
The general rule of thumb is that larger, more horizontal, and easy-to-wet surfaces are better suited for coarser sprays – they are intercepted more efficiently and stick readily. That’s one reason why most broadleaf weeds and crops are very compatible with low-drift sprays.
On the other hand, smaller, vertically oriented, and difficult-to-wet plants require finer sprays. Larger drops tend to miss these targets or bounce off them. Most grassy weeds and some broadleaf weeds (especially at early growth stages) are in this category.
The mode of action is the way in which the herbicide, insecticide, or fungicide controls the target. It also describes the biological process or enzyme that the chemical interrupts, affecting normal growth or development of the target. Sometimes, the MOA may be a generalized description of the symptoms seen on vulnerable plants.
There are nearly 30 MOAs in the herbicide world, another 10 modes for insecticides, and 15 for fungicides. Knowing a little bit, generally, about each MOA is a critical step in choosing the proper herbicide, insecticide, or fungicide for each crop, diagnosing crop injury, and designing a crop management program you can implement effectively. Overreliance on a single MOA – or active ingredient – may eventually lead to resistant weeds that will multiply and become dominant in a field over time.
The impact of droplet size and water volume on uptake and translocation (the movement of the chemical from leaves to other tissues in the plant) varies among MOAs, so it’s important to recognize and consider this when using various MOAs. The best source of information will always be the product label.
Successful sprayers establish a good routine but plan for the unexpected. Not all, but many farming operations are making the same type of routine applications that are broad-spectrum, targeting large and small broadleaf and grassy plants.
You want to establish a good working process to approach all of your spraying applications, with enough time for preparation and planning up front, but plan for flexibility when things you cannot control pop up. Many sprays include tank mixes of several modes of action.
Keeping detailed records, testing before you spray, and understanding how each MOA and tank mix partner interacts — both in the tank and when sprayed on the crop — can make all the difference. You may have to adjust if you incorporate a new cover crop or plant a new seed variety, depending on your crop rotation.
Every consideration in your cropping plan can impact your chemical management plan and affect your approach to your spray applications.
FBN helps farmers manage input costs and maximize their ROI by offering high-value crop protection solutions at competitive prices. The FBN platform and free mobile app are designed to make it easy to do business, with an online store available 24/7 and convenient direct-to-farm delivery.
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