Targeted crop spraying is grabbing headlines. Conservative estimates put potential herbicide savings for postemergence applications near 50%, and some much higher. What’s the catch? Achieving savings requires upfront investment, from as low as $25,000 plus per-acre costs up to $250,000 or more, depending on which system you choose.
What if you could target-spray weeds with your current sprayer but without buying a retrofit system? The catch may not disappear completely. Your sprayer still may need an upgrade to control nozzles individually, which is required for targeted spraying retrofit systems, too. And this concept uses drone scouting. But compared to buying a new sprayer or retrofit unit, entry level costs could be much lower.
Test the concept
Doug Houser, digital agriculture specialist with Iowa State University Extension, reports that ISU successfully demonstrated merging drone technology for weed mapping with a self-propelled sprayer platform to target-spray weeds and cut herbicide usage on a soybean postemergence pass in 2024.
“We used a John Deere sprayer not equipped with See & Spray but outfitted with John Deere ExactApply, allowing individual nozzle control,” he explains. “We used Sentera’s Aerial WeedScout drone technology to generate a customized herbicide prescription within 24 hours after the drone flight.”
Houser notes that other sprayer companies offer individual nozzle control options. There are also other companies offering scouting images through drones or satellites. They include Intelinair, Pix4D and Taranis. However, as far as Houser knows, Sentera is currently the only company offering fully automated targeted-spray prescription generation that works effectively with postemergence spray timing in soybeans.
Recently, Sentera relabeled Aerial WeedScout as SmartScript Weeds. There is a waiting list. To learn more and get on the list, visit sentera.com.
Promising results
The prescription determined when nozzles turned on and off. There were no cameras on the spray boom. Just under 9 acres were sprayed by prescription in the trial, resulting in a savings of just under 50%, or $13.42 per acre. All herbicides were applied at rates within product labels.
Savings align well with typical savings with targeted sprayers with cameras. In a separate ISU study looking at targeted spraying, herbicide savings ranged from 42% to 91%, Houser says. Savings with targeted sprayers fluctuate depending on weed intensity and settings for the size of area to be sprayed around a weed. The lower the weed pressure, the higher the savings, Houser explains.
Weed counts before and 17 days after indicated that 99% of weeds were injured, and 94% were killed by the prescription application based on the drone flight. Yield was within 1.5 bushels per acre of the control, where the entire area was sprayed. These yields were not significantly different, meaning the difference could be due to experimental error.
More work needed
Houser is not the only researcher looking at this opportunity. In Indiana, Tommy Butts, Purdue Extension weed control specialist, also experimented with weed mapping by drone in 2024. He called it do-it-yourself, or DIY, drone mapping.
“We developed weed maps from drone flights over soybeans and then developed prescriptions,” Butts says. Those prescriptions can be used by a self-propelled sprayer or a drone sprayer to apply herbicides only where weeds are detected.
“It is not 100% foolproof yet,” Butts says. “We are making progress and will continue working on it so that it can detect weeds correctly for a higher percentage of the time.”