Photo by Erdal Ozkan.

Limitations of spray drones and obstacles to their adoption

By Erdal Ozkan

Acceptance of spray drones by individual farmers has been slow for several reasons:

  1. Not enough research data comparing drone performance (e.g., efficacy and spray drift) to ground sprayers and conventional aircraft is available. The limited published data on performance of spray drones may not be usable and can be contradictory because of the wide variation of design parameters among drones being tested.
  2. Fewer acres are covered per hour of operation compared to airplane and ground sprayers.
  3. The battery powering the drone lasts a short time (5 to 15 minutes with a full tank) and requires recharging between tank refills. Having three charged batteries per drone and fast charging at 240v eliminates long interruptions in spraying to charge the drone’s battery. Maintaining three charged batteries allows replacement of a discharged battery while refilling the spray tank. The spent battery can then be recharged and ready for the next refilling.
  4. The FAA imposes several operational restrictions on drones, such as: a drone must weigh 55 pounds or less including its payload, the pilot flying the drone must maintain a visual line of sight with the drone, permission must be obtained when flying in restricted air space, and drones can be flown only from 30 minutes before sunrise to 30 minutes after sunset. Perhaps the most severe restriction is that an operator can fly only one drone at a time. However, swarm spraying is practiced legally and successfully in other parts of the world, especially in southeast Asia, mainly China, South Korea, and Japan. Fortunately, the FAA allows pilots to apply for waivers for several of these limitations, such as the 55-pound maximum weight of the drone sprayer, night spraying, and maintaining a line of sight.
  5. Chemical product labels do not provide clear information related to drone spraying. Some labels do not allow aerial application of any form. Some labels allow aerial application of the product, but don’t specify the type of aircraft that can be used. Currently, no pesticide label provides specific instructions on how the product can be sprayed using a drone. It is anticipated that pesticide labels will eventually refer to drone spraying. The EPA allows drone use for spraying if the pesticide is already labeled for conventional aerial application and if FAA rules for operating drones are followed.

Future of spray drones 

Drone sprayers will never replace ground or conventional aerial application technology, but they may complement existing spray practices because of the opportunities they provide as mentioned earlier in this article. The future of drone spraying will be mainly affected by the economics, timeliness of crop protection (i.e., which option may get the job done in the shortest time), the type of spraying to be done (broadcast vs. targeted), and availability of local companies offering drone sprayingAlthough drone spraying does not seem to be a viable option to compete with ground sprayers with wide booms and conventional, piloted aircraft in the application of pesticides to large fields, some companies offering drone spraying indicate that their rates are competitive with or even more economical than the cost of spraying done by ground equipment and conventional aircraft. 

Acceptance and adoption rate of spray drones by individual farmers is likely to increase in the near future due to following changes in regulations and technological upgrades:

  1. FAA regulations and restrictions on use of drones may be eased, especially restrictions on “swarming,” in which multiple drones are operated by one pilot or autonomously.
  2. Improved design and manufacturing may result in longer lasting batteries, wider spray width, higher flow rates, and faster operational speeds.
  3. Larger drones with larger sprayer tanks may be designed and possibly approved by the FAA.
  4. Upgrades to drone technology may result in improved variable-rate application, precision spot spraying and route planning, and better obstacle avoidance.

Additional information 

Flying a drone is subject to many restrictions, including a requirement that the pilot be at least 16 years old and that the drone has a maximum weigh of 55 pounds, unless an exemption is granted. To find out all the requirements to be a drone pilot, obtain the pilot certificate (FAA Part 107), and legally apply pesticides using a drone (part 137), visit the FAA web site at Another informative and useful resource is the FAA Remote Pilot Study Guide at

Prospective pilots can also do an internet search for “FAA remote pilot study guide.” Topics covered include airspace classification, operating requirements and flight restrictions, effects of weather on aircraft performance, emergency procedures, radio communication procedures, determining the performance of aircraft, physiological effects of drugs and alcohol on pilot performance, and registration and marking requirements. A web site prepared by Alan Leininger, Extension educator in Henry County, Ohio, is also an excellent source of practical information related to drone spraying and the FAA requirements for certification to fly a drone. Leninger’s website is located at

The Ohio Department of Agriculture’s (ODA) website is another resource that includes information on the application of pesticides using drones. This website provides answers to many of frequently asked questions such as, “What pesticide licenses are required by ODA to apply pesticides via a UAV (aerial drone)?” It can be accessed at

An important topic that is not covered in this article is the Federal (FAA) and State regulations related to using drones to spray pesticides. Two certificates must be obtained from FAA to spray using drones: an FAA “Part 107 Certificate” to fly a drone and a “Part 137 Certificate” to apply pesticides using drones or to apply pesticides using drones while under the direct supervision of a person who holds this certificate. However, spraying pesticides in Ohio requires more than these two FAA certificates. An applicator must also complete the Ohio Commercial Pesticide Category 1 training course, which covers “the application of pesticides, except fumigants, by aircraft.” 

Detailed information on how to obtain these licenses are given in a new Ohio State University Extension Publication FABE-540 titled “Drones for Spraying Pesticides — Opportunities and Challenges. The link to access this publication is: The PDF version of the publication is also available at:

Erdal Ozkan, Professor and Extension ag engineer, can be reached by email at This column is provided by the OSU Department of Food, Agricultural and Biological Engineering, OSU Extension, Ohio Agricultural Research & Development Center, and the College of Food, Agricultural and Environmental Sciences.

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