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A PAC Cresco topdressing.

Polish M-18 Dromader waterbomber used in Western Australia.

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.

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.

A crop duster applies a low-insecticide bait on a soybean field.

The first known use of a heavier-than-air machine occurred on 3 August 1921 when as the result of advocacy by Dr B.R. Coad, a United States Army Air Service Curtiss JN4 Jenny piloted by John MacReady was used to spread lead arsenate to kill catalpa sphinx caterpillars near Troy, Ohio in the United States. The first commercial operations were attempted in 1924, by Continental Dusters which subsequently became part of Delta Air Lines. Use of insecticide and fungicide for crop dusting slowly spread in the Americas and to a lesser extent other nations in the 1930s and 1940s.

NZ Ministry of Works Miles Whitney Straight ZK-AFH, the first aircraft to used for topdressing

Aerial topdressing, the spread of fertilisers 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.

A helicopter fills its bucket while fighting a fire near Naples, Italy.

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.

Crop dusting at night is mostly liquid spray and is conducted in the Southwest US 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 and helicopter) 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 taxi and wire or obstruction illumination; and turn lights which only were 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 channels built in to direct the flow of dust such as sulplhur, 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 because of new laws regarding using human flaggers on some pesticides.

According to the US Bureau of Labor Statistics, in 2005 US cropduster pilots earned an average annual wage of $63,210.