
Targeted or spot-spraying technology is coming to crop fields, ready or not. Over a dozen systems globally are available that use artificial intelligence and machine learning to shut off nozzles where there are no weeds or reduce labeled rates where weed pressure is low.
After listening in on numerous webinars and live discussions, one point is clear: Make the effort to understand the terminology so you don’t fall into the trap of thinking this technology allows you to cut rates below labeled rates if weed pressure is light.
Bill Johnson, Purdue Extension weed control specialist, believes that would be a recipe for disaster. “Guys will be tempted to cut rates this year anyway because margins are tight,” he says. “If you must cut your budget, trim somewhere else, not on weed control. Instead, think about applying residual herbicides and post products at full rates tough weeds like waterhemp don’t escape.”
Understand weed control terms
Here is where confusion could arise. If someone suggests possibly saving money by reducing herbicide rates through targeted spraying, they’re talking about applying lower but still labeled rates where weed pressure is light. There are systems with cameras trained to determine weed pressure based on algorithms. These algorithms incorporate weed size and density at a given spot. That may allow you to apply a reduced labeled rate where pressure is low.
But it is still a labeled rate. Where people run into problems with weed control is when they apply a reduced rate lower than labels allow, Johnson says. For example, if the lowest labeled rate is 1 quart per acre and you apply 1.3 pints where weed pressure is low to save money, that is cutting rates. You may not get the weed control you hope, and you may promote resistance because lower-than-labeled rates may not kill tougher weeds.
Precision Planting is launching two camera-based upgrades to its SymphonyVision spraying systems in 2025. Jason Stoller, director of product engineering, says the upgrades, SymphonyVision Rate and SymphonyVision Spot, will allow growers to apply reduced labeled rates where weed pressure is light. The Spot upgrade lets the grower program the sprayer to shut off nozzles where cameras don’t detect weed presence.
Stoller emphasizes, however, that in no case is Precision Planting recommending setting either system to apply less than the labeled rate of any herbicide.
Fact is, he notes, that many labels recommend a range of rates, from low to medium to high, based on weed pressure. Weed size and density, or number of weeds per square foot, determine weed pressure.
Going across real farm fields, weed pressure will shift. If you can’t vary application rate to match shifting weed pressure, you pick a compromise rate, still on the label. Often, that means you are applying a labeled rate higher than necessary where weeds are small and/or scarce, but less than what the label recommends for big weeds or patches of weeds.
Targeted or spot-spraying systems allow you to apply the right labeled rate where needed, Stoller says. That should result in better weed control and also could save money because less chemicals are applied where weed pressure is lighter.
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