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Randy R. Price
Sprayer drones are a new tool available to farmers, consultants, and aerial applicators. Still, these devices are relatively new, and not much is known about the flight characteristics, operational procedures, or the application patterns or drift. This article will explore the current status of sprayer drones, common sprayer drone concepts, and the future precision farming aspects of these devices.
Availability
Much has changed since last year. China was the leading manufacture and all but dominated foreign and U.S. markets. Then in December 2025, a new law came into effect that mandated that any drone sold in the U.S. had to be manufactured by a company that is at least partly based in the U.S. This greatly changed the landscape of drones in the U.S., giving U.S. companies a chance for market success and survival against low-cost Asian brands. Now we have DMR, EAVISION, Talos (which manufactures and sells a DJI style drone), Hylio, and various other companies (Ceres Air, etc.).
Sprayer Drone Use in Louisiana
We are seeing a continued increase of sprayer drones in Louisiana. Operators are still not spraying as many acres as manned aircraft (or even close), but numbers are growing each year. One manufacturer stated that Louisiana will be a prime state for sprayer drone sales with farming occurring nearly 10 months out of the year. In fact, a sprayer drone calibration day was held at the Iberia Station by Kim Landry, Jeremy Hebert, and Randy Price, and turnout was quite high with more than eight companies with 15 drones. We saw drones from almost every type of drone sold in the U.S. and learned a vast amount about their operation and typical spray patterns. In addition, pilots got to meet other people in their industry and discuss various flight patterns and operations, which greatly helps spread good operating techniques for better and more efficient spraying. We will probably have another calibration day next year (mid-March) for those interested.
Cost
Currently sprayer drones are inexpensive (compared with other agricultural equipment purchases), as they cost between $10,000 to $50,000. Typically, they come as kit with all items needed to operate: sprayer drone, controller, three batteries and a high-speed charger. Keep in mind that you will also need a service truck or trailer with tanks, mixing equipment, high-capacity pumps (greater than 10 gallons per minute), and a large generator (13,000 to 27,000 watts). All these items, depending upon setup, can cost more than the drone itself. Look around before purchasing or building a service trailer or truck. There are many ideas out there, including single truck bed units (RoadRunner truck bed system, etc.) to full-size trailers with foldout walls and large upper deck platforms. This is where you can possibly design and build your own trailer. Note that low-cost tank mixing in the drone itself is possible, but we have had substantial problems using this method as most drones do not have any type of tank agitation, and multiple areas in sugarcane fields have been killed or damaged using this method. Be careful and make sure chemicals are thoroughly mixed!
Current Rules
To operate a sprayer drone in Louisiana, you will need multiple licenses from both the federal and state government, including:
On the state of Louisiana side, you will need to pass several different commercial applicators knowledge tests and register the drone every three years with the Louisiana Department of Agriculture and Forestry (LDAF). Note that many drone companies will help you obtain and file this paperwork.
Calibration
An important aspect of using your sprayer drone is getting to know its flight properties and spray characteristics. Each drone has a travel speed, application height, nozzle setting (rotation speed, etc.), and flowrate that creates the best and most efficient application pattern and swath width. Determination of these aspects can be quite hard with visual cues alone, and pattern testing is needed. The LSU AgCenter has pattern testing equipment that can help you determine these aspects. In addition, Facebook pages and social groups on the internet can help you learn the typically used and best settings for your drone. Note that most people operate their drones in an extended spray settings for economic or time efficiency. Spraying wider than those settings that create the most uniform coverage, which is many times O.K. for insecticides and fungicides, may not work well on other work such as ripener or burndown. Sugarcane ripener application typically needs more uniformity and tighter swath widths to create high total recoverable sugar levels and not damage stands. We typically recommend running two-thirds of what the manufacturer says for swath width. Also, in ripener work, watch around field ends and work around telephone poles, as reduced application speeds can cause a 50% or more decrease in swath width, doubling the amount of ripener application in those areas and killing the sugarcane. Running smaller than normal swath widths will help alleviate this problem in ripener applications. I also highly recommend doing some test flights with water before spraying, and spraying over a dry road or parchment paper can help you determine correct spray widths.
Proper Spray Patterns
When flying a drone properly, you should see a curtain of liquid come out the back of the drone that looks like the long hair flowing from the back of a person’s head that curls right before the spray enters the crop. If you see extensive vaporization and misting, your droplet size is too low and you should increase the droplet size by either slowing the rotation speed of the nozzles or picking a larger size on the controller settings. Note that 300 microns (um) or larger droplet will be barely visible in most cases during spraying. Also, note that in previous calibrations with newer drones, most were outputting 300 um droplets regardless of larger droplet size settings. This setting can be determined by flying over a strip of water-sensitive paper (available from TeeJet and other vendors), where a 300-um droplet should make a water spot about the size of a ball point or sharpened pencil end.
Best Environmental Condition
On the environmental side, drones seem to work best when the winds are nonexistent or low and constant. High winds (greater than 8 mph) and/or highly variable winds (changes greater than 6 mph) can cause large disruptions and movement of the spray pattern. In testing, 300-um spray patterns from drones could move up to 70 feet downwind in 10 mph crosswinds, creating large offsets in the spray pattern. Also, because of the flat trajectory of the droplets leaving the rotary nozzles, a few droplets are always thrown 20 to 30 feet from the center of the drone. For this reason, care should be taken when flying near borders, edges of fields, sensitive areas or spraying levees with sensitive crops nearby. Flying lower may help this aspect.
On the inversion side, inversion-prone chemicals (2,4-D, Dicamba, etc.) can still be a problem, but drones seem to have enough blow down (currently) from propellers to push the chemicals and spray pattern to the top to the crop. In addition, properly adjusted drones (correct droplet sizes, etc.) don’t seem to have the kick-up and upward heaving vortices associated with full-size aircraft, negating spray that is carried above the vehicle. Only time will tell if this property holds true, as drones become larger, faster and more like current full-size aircraft and helicopters.
Future Precision Farning Aspects
The future aspects of precision farming with sprayer drones is quite good. Their small sizes (smaller than 20 gallons), swath widths and automated flight capabilities lend them well to performing site-specific farming applications. Still, they are rarely used for this purpose because economically viable variable rate solutions just don’t exist. If they did, I guarantee everyone would be using them. Still, sprayer drones are well suited for this type of application because they are able to easily treat small areas with different tank loads (users must remember to thoroughly mix chemicals). Perhaps future developments will help out this area where the LSU AgCenter is currently looking at variable rate ripener applications, although split “blanket” applications may be the next wave of the future!
Notes About First-Use Drones
If you do purchase a sprayer drone and are new to its operation, you should spend some time with a company representative doing a “first flight” as the buttons and the startup procedures can be quite confusing and vary greatly between different manufacturers and drones. Even a small video will help! Also, you should obtain the number for a person with the company who can quickly answer questions as they arise. Also, make sure that the company has a good parts supply and method to get these parts, as most drones will need repairs at some point in time.
Drone Resource List
If you are interested in purchasing or learning about sprayer drones, more common ones are listed here:
If you have any questions, comments, or need a drone tested, you can contact Randy Price at [email protected] or 225-936-7593.
A sprayer drone is tested on a sugarcane field near the LSU AgCenter Dean Lee Research and Extension Center. Photo by Kyle Peveto
A sprayer drone flies over a sugarcane crop during a test at a field in Alexandria, Louisiana, while another drone sits on the ground. Photo by Kyle Peveto
