Aerial application, commonly called crop dusting, involves spraying crops with fertilizers, pesticides, and fungicides from an agricultural aircraft. The specific spreading of fertilizer is also known as aerial topdressing.
Agricultural aircraft are often purpose-built, though many have been converted from existing airframes. Helicopters are sometimes used, and some aircraft serve double duty as water bombers in areas prone to wildfires.
Aerial seed sowing 1906 
The first known aerial application of agricultural materials was by John Chaytor, who in 1906 spread seed over a swamped valley floor in Wairoa, New Zealand, using a hot air balloon with mobile tethers. Aerial sowing of seed has continued on a small scale.
Crop dusting 1921 
The first known use of a heavier-than-air machine occurred on 3 August 1921. Crop dusting was developed under the joint efforts of the U.S. Agriculture Department, and the U.S. Army Signal Corps's research station at McCook Field in Dayton, Ohio. Under the direction of McCook engineer Etienne Dormoy, a United States Army Air Service Curtiss JN4 Jenny piloted by John A. Macready was modified at McCook Field to spread lead arsenate to kill catalpa sphinx caterpillars at a Catalapa farm near Troy, Ohio in the United States. The first test was considered highly successful. The first commercial operations were begun in 1924, by Huff-Daland Crop Dusting, which was co-founded by McCook Field test pilot Lt. Harold R. Harris. Use of insecticide and fungicide for crop dusting slowly spread in the Americas and to a lesser extent other nations in the 1930s.
Top dressing 1939–1946 
Aerial topdressing, the spread of fertilizers such as superphosphate, was developed in New Zealand in the 1940s by members of the Ministry of Public Works and RNZAF, led by Alan Pritchard and Doug Campbell - unofficial experiments by individuals within the government led to funded research. Initially fertilizer and seed were dropped together (1939), using a window mounted chute on a Miles Whitney Straight, but by the end of the 1940s different mixtures of fertilizer were being distributed from hoppers installed in war surplus Grumman Avengers and C-47 Dakotas, as well as some privately operated de Havilland Tiger Moths in New Zealand, and the practise was being adopted experimentally in Australia and the United Kingdom. Crop dusting poisons enjoyed a boom after World War II until the environmental impact of widespread use became clear, particularly after the publishing of Rachel Carson's Silent Spring.
Water bombing 1952 
Aerial firefighting, or water bombing, was tested experimentally by Art Seller's Skyways air services in Canada in 1952 (dropping a mix of water, fertilizer and seed), and established in California in the mid-1950s.
Night aerial application 1973–present 
Crop dusting at night is mostly liquid spray and is conducted in the Southwest U.S. deserts. The rising cost of pesticides and increasing immunity built up by continuous spraying reduced the effectiveness of spraying in daytime. In high temperature areas, the insects would travel down in plants in daytime and return to the top at night. The aircraft — both fixed wing, autogyros and helicopters — were equipped with lights, usually three sets: Work lights were high power and aimed or adjustable from the cockpit; wire lights were angled down for taxiing and wire or obstruction illumination; and turn lights were only turned on in the direction of the turn to allow safe operation on moonless nights where angle of entry or exit needed to be illuminated. These aircraft were equipped with pumps, booms, and nozzles for spray application. Some aircraft were equipped with an elongated metal wing called a spreader, with inbuilt channels to direct the flow of dust such as sulfur, used on melons as a pesticide and soil amendment. Very little pesticide dust was used day or night in comparison to spray, because of the difficulty in drift control. Workers on the ground, called "flaggers", would use flashlights aimed at the aircraft to mark the swaths on the ground; later, GPS units replaced the flaggers due to new laws restricting use of human flaggers with some pesticides.
According to the U.S. Bureau of Labor Statistics, in 2005 U.S. cropduster pilots earned an average annual wage of $63,210.
Environmental and human health issues 
As with pesticide application in general, crop dusting is associated with a number of environmental concerns, including spray drift, soil contamination, water pollution, and occupational disease, often in the form of increased risk of cancer to those involved. In addition to their impact on human health, there is also concern that the use of pesticides can lead to the development of resistance among insects. By 1970 in the United States, lawsuits and court cases involving spraying of pesticides, especially aerial application in commercial agriculture were a growing area in law, combining areas such as negligence, products liability, strict liability, statutory regulation and commercial law. Environmental and human rights issues associated with crop dusting are greatest in developing countries, where government oversight is weaker or absent, few safety practices are used, and chemicals are used that are banned in most developed countries.
A study found that most of the crops grown in Texas were treated with chemicals that show evidence of possible carcinogenicity, and pointed to aerial application of pesticides as a potential cause of cancer in children. Crop dusting involving arsenic powders has been implicated in Bowen's disease. A study found that aviation mechanics in Nicaragua who work on planes used in the aerial application of pesticides are at high risk for poisoning due to contamination on parts of the aircraft. Also in Nicaragua, water runoff from a crop-dusting airport has been linked to contamination of the supply of drinking water, leading to levels of toxaphene far exceeding the limit the United States Environmental Protection Agency set in the U.S.
See also 
- Pesticide application
- Ultra-low volume spray application
-  National Agricultural Aviation Association
- Johnson, Mary Ann. McCook Field 1917-1927. Landfall Press, Dayton, Ohio: 2002. ISBN 0-913428-84-1, pp. 190-191.
- William T. Birmingham; Jon L. Kyl, "Legal and Practical Aspects of Pesticide Spraying Cases", Defense Counsel Journal, (1970)
-  K. Elgethun; S. Horel; S. Carozza "Pesticide Exposure Assessment for a Population-Based Case-Control Study of Childhood Cancers", Epidemiology:Vol. 17, No. 6, Suppl., (Nov. 2006)
- H. Luchtrath, "The consequences of chronic arsenic poisoning among Mosalle wine growers: Pathoanatomical investigations of post-mortem examinations performed between 1960 and 1977", Journal of Cancer Research and Clinical Oncology, No. 105, pp. 173-182 (1983)
-  R. McConnell; A.F. Pacheco Antón; R. Magnotti, "Crop duster aviation mechanics: high risk for pesticide poisoning", American Journal of Public Health, Vol. 80, No. 10, pp. 1236-1239, (1990)
-  Rob McConnella; Feliciano Pachecob; Kåre Wahlbergc; Willy Kleinb; Omar Malespinb; Ralph Magnottid; Malin Åkerblome; Douglas Murray, "Subclinical Health Effects of Environmental Pesticide Contamination in a Developing Country: Cholinesterase Depression in Children", Environmental Research, Vol. 81, No. 2, pp.87-91. (Aug. 1999)
- Johnson, Mary Ann. McCook Field 1917-1927. Landfall Press, Dayton, Ohio: 2002. ISBN 0-913428-84-1, pp. 190–191.