Sprayer and plant-protection drones are new tools available to farmers and can be used to apply pesticides to small land areas and acreages. This type of sprayer can access land that is either too wet or otherwise inaccessible by humans and can provide greater spray infiltration into the plant canopy. Also, people are removed from spraying operations, which can greatly help reduce chemical contamination to humans. The disadvantages are that most sprayer drones can only carry 1 to 2 gallons of liquid and only fly for 10 to 20 minutes. For commercial use they may require fairly rigorous certifications, including Federal Aviation Administration Regulations Part 137 and Part 107 and other state and local certifications. Still, plant-protection drones may be useful in Louisiana, where the wet climate and different types of crops, including rice, horticulture and others, create a large need for small-area spraying. They may also be beneficial in areas inaccessible to trucks or spray planes. Typical uses in Louisiana are spraying levees, fence rows, briar patches, horticultural and vegetable plots, and tight field areas with obstructions. Note that these sprayers create a large air blast to hold the drone up, so spraying heights are typically higher (10 to 12 feet) than regular ground sprayers, and some damage can occur to fragile crops if the spraying height is too low.
Buying a plant-protection drone can be quite expensive, costing $15,000 or more. We have found that it is possible to build your own sprayer and plant-protection drone in the $2,000-to-$3,000 range. Free software is available (www.DIYdrones.com) that has advanced to the point that height and position can be held to exact levels with a good range finder. Sprayer kits are also available from manufacturers. An example of a sprayer drone we built for under $2,500 is shown in Figure 1.
This drone carries three-quarters of a gallon of liquid, has a 10-minute flight time, is easy to fly and was constructed from the following components:
If you don’t feel like building a sprayer drone, some older models can be found on the internet in the $5,000-to-$8,000 range. If you do build your own, note the following:
Note the following when selecting ESCs (electronic speed controller):
During operation, keep the following in mind:
The original green flat-fan nozzle tips that came with the spray system produced an extreme amount of driftable fines in the spray pattern. We used yellow A.I. (air induction) flat-fan tips at low pressure (0.1 GPM) to produce the droplet size pattern shown in Figure 2. These nozzles greatly reduced the driftable fines in the spray pattern (Figure 3). Note that the nozzles were spaced 40 inches apart on the boom, which is greater than a typical spray system but still gave a 6-foot uniform application (Figure 2) at an 8-to-10-foot flying height. Note that if you attain a sprayer drone and want the application pattern and droplet size tested, LSU AgCenter has the facilities and equipment to determine these properties.
Figure 2: Droplet cards spaced every 1 ft. at a 8- to 10-foot flying height yielding a 6 ft. spray pattern (Vmd 0.5 = 467 um; Vmd 0.1 = 251 um; Vmd 0.9 = 644 um; 0.1 GPM per nozzle; 3.2 gpa).
Figure 3: Droplet cards from drift pole located 30 feet downwind compared to other nozzles tested — four consecutive passes; 4 to 6 mph crosswind; 58 percent RH; 82oF; 0.002 GPA drift per pass.
Building your own drone can be fun and informative, and a sprayer drone can add spraying utility to your farm that was not possible before. Note that regulations do exist for spraying commercially, and you will need Federal Aviation Administration Part 137 and Part 107 certifications along with other state and local certifications and an FAA flight test of the drone.
If you have any questions or need help setting up a drone, Dr. Randy R. Price can be reached at: LSU AgCenter Dean Lee Extension and Research Center, 8105 Tom Bowman Drive, Alexandria, Louisiana. Price can also be reached by email at firstname.lastname@example.org.