In the Alfred Hitchcock movie, ‘North by Northwest’, a Stearman crop-duster aircraft, chased Cary Grant across an open field with the intent of killing him. Thankfully, this was just a movie, and not indicative of the real purpose of crop-dusters!
Crop-dusting got its start in the southern United States during the 1920’s, to provide protection for the cotton fields against the boll weevil insect, where cotton was ‘king’. The first crop-duster was Army Lt. John Macready in the year 1921 -a fighter pilot in WWI. He would have been very proficient at maneuvering a plane ...a very, very necessary skill.
In the early days (1920’s), aerial applicators were known as ‘crop-dusters’, because they worked primarily with dry chemicals, mostly insecticides. The first planes used were converted war-surplus biplanes, such as the De Havilland Tiger Moth, and Stearman. Aircraft eventually became custom- designed for crop-dusting, and in those early days, most were yellow for visibility so that higher flying planes could readily see the crop dusters, below.
During the 1950’s, crop-dusting became increasingly popular due the large numbers of surplus WWII airplanes. At that time, a farmer might only spray 100 acres/day with small tractor-drawn ground sprayers, while a plane could cover 60-70 acres per hour.
Crop-dusting is not exactly a ‘dare-devil’ profession, but something like that, as it takes a lot of nerve and skill, as at times, they might have to fly under hydro wires to come-in close to a field, and take-off abruptly at the edge of a wooded area. And, to help reduce pesticide drift, aircraft would often fly within 6’-8’ off the ground, travelling at 100 mph!
At times, night-time applications were used as the insects would come out to feed in the protection of darkness, resulting in higher kill rates, and make the exercise more economical. It was also to help reduce insect resistance to insecticides, that often resulted from over-use and continuous spraying.
Presently, there are about 1,500 aerial application businesses in the U.S., that treat upwards of 25% of America’s cropland. The low-wing Piper PA-25 Pawnee is now the favoured plane for crop-dusting.
More locally, crop-dusters can be seen applying pesticides and fertilizers on area crops. Often, this is done in the evening or early mornings, when the weather is calmer, reducing the chance of spray drift on unintended targets. During periods of wet weather, there is increased demand for spraying services, but the windows of opportunity for spraying also decreases creating a ‘shortage’ of planes and pilots.
In the Norfolk and surrounding region, crop-dusting (spraying) is still applied on some crops, potato and pumpkin, for example, and mainly for disease control. Corn and soybeans are also sprayed for pests. When severe infestations of gypsy moth invade area forests, it is crop-dusters to the rescue. Crop-dusting is not as popular as it once was when tobacco was ‘king’ and the mainstay of the aerial spraying business. Now tobacco growers have their own ground-rig equipment making aerial spraying almost obsolete for this crop.
Most other growers also have very effective and efficient self-propelled ground sprayers that are highly engineered to do the job at a high level of accuracy. A sprayer with a 120’ boom travelling at 10 mph, can cover 300-400 acres per day, depending upon circumstances.
However, if ground conditions are too wet to travel on, and there is a critical need, crop-dusters can still be called upon to do the job. In addition, some crops such as pumpkins and squash, for example, row-in such that land rigs cannot travel through the crop without doing considerable damage -and, therefore, aerial aircraft applications are about the only solution.
At times, both planes and helicopters, are called upon for frost control. By creating turbulence, mixing the air can raise the ambient temperature to non-freezing levels. Vine crops and pepper blossoms are particularly sensitive to frost and cold temperature injury.
Crop-duster pilots are highly skilled at what they do; the plane, becomes an extension of themselves as much depends on the performance of the aircraft. There becomes an innate sense of ‘artistic feel and finesse’ with pilots and their plane, as crop-dusting is not an ‘exact science’.
There is little room for error at such low altitudes and high speeds. And, it might be said, that every flight is a ‘close call’. As fields can be small, pilots often have to dive into them very aggressively, given there is insufficient space for a more gradual approach. Pilots are professionals in every sense of the word, airplane maintenance is absolutely key, it is all a matter of life and death!
The Pawnee was one of the first purpose-built aircraft for crop-dusting, and has a large engine (250 hp) for such a light-weight plane. Although there is little in the way of instrumentation in the plane, oil pressure is paramount, and so is the fuel gauge! Unlike at higher altitudes, there is no place to glide to a safe landing at 100 mph and only 6’ off the ground.
Plane performance changes greatly with the amount of pay-load. A Pawnee could carry 1,200 lbs of pesticide, but during the last 25% of the load the plane becomes lighter, and much more responsive to the point of almost becoming a ‘hot-rod’ -and, as one pilot said, “the last quarter tank is all fun”.
Cool crisp days are better for plane aerodynamic performance than during hot and humid weather. Humidity displaces oxygen which is needed for fuel combustion, and engine fuel doesn’t burn as fast. As air temperature and altitude increase, air density decreases and negatively affects flight performance as there is less ‘lift’ for the plane; this is known as the ‘density altitude’ factor
At high rates of application, a small crop-duster can empty its payload (of 100 gallons) in 3-4 minutes, although 15-20 minutes is more common. Therefore, much of the time is spent flying back to base for refilling and refuelling.
Even today, when crop-dusters are seen in local fields, it is not uncommon to see passers-by pull over to the sides of roads to admire the aerobatics of these very skilled pilots, ‘dare-devils’ of the sky.