A growing trend in U.S. agriculture is more farmers and ranchers are purchasing equipment to apply pesticides versus hiring custom applicators.

Many producers have either never sprayed or it has been a long time since the last application. Meanwhile, the pesticide application industry has changed dramatically.

A major emphasis in pesticide application education and training is underway to assist these applicators in the safe and efficient use of current pest control equipment.

Robert Wolf shared a plethora of knowledge on this subject during the Southwest Ag Summit in Yuma, Ariz., in March. Wolf recently retired as professor and application technology specialist with Kansas State University (KSU) and now operates Wolf Consulting & Research LLC in Mahomet, Ill.

The bottom line, Wolf said, “Accurate and efficient pesticide applications should increase efficacy, minimize drift, and maximize productivity.”

Nozzles can increase efficacy but lead to more drift potential. Some newer nozzles can produce larger spray droplets to decrease drift but at the same time can result in reduced coverage for controlling the targeted pest.

For pesticide applicators, it is easy to think that ‘big is better’ when it comes to application equipment; a larger spray boom on a ground rig or a larger tank on a powerful airplane. While large application equipment can be effective in the right situation, Wolf says larger equipment can reduce pesticide efficacy and increase drift especially if operating at higher speeds.

Sticker shock also comes with larger equipment. A 120-foot, fully equipped, commercial size self-propelled sprayer capable of marching down a field in the Midwest at 20 to 25 miles per hour can fetch $250,000 to $300,000. In the West, a recent model turbine-powered airplane dropping chemical over a field at a white knuckling 160 miles-per-hour can debit the farm’s books by several million dollars.

Most university and government-based research facilities lack the equipment and especially the wind tunnels capable of measuring chemical efficacy and spray drift at higher rates of speed. The USDA-ARS wind tunnel at College Station, Texas, was recently upgraded to test spray applications delivered at a globe-trotting 220 mph.

Ground rig or airplane?

Is a ground rig or an airplane more effective at applying pesticides? Wolf says each delivers pesticides effectively; one is not better than the other. However, it is possible to cover more acres with an airplane which can be an advantage in certain situations, including wet ground conditions, short application windows, and growing crops with a canopy.

Modern spray systems have similar components: poly or stainless steel tanks; pumps, strainers, and agitation; pressure gauges; hoses and flow control assemblies; electronics including monitors, computers, and controllers utilizing GPS/GIS technology; a distribution system; and spray nozzles. The GPS/GIS system especially adds to the higher price and makes some sprayers different than others.

New developments in sprayer technology include improved flow back control for better chemical shutoff. New nozzle body turrets hold up to five different-type and size nozzles and spin the nozzles 360 degrees to provide more flexibility and improved flow.

Other advances include improved rate controllers, GPS-based auto steering, and advanced automatic boom section control which helps applicators reduce double spraying (overlaps) and avoid skips.

“The more sections you can control on the boom the better,” Wolf explained. “Some companies are working their way toward a control for every nozzle. At that point we’ll be at the ultimate in variable rate possibilities.”

A KSU farm management and agricultural economics group website located at www.agmanager.info is designed to help applicators determine the affordability of automatic boom control advancements. The technology pays for itself sooner when used on irregular-shaped fields.

While the spray machine is important, Wolf says the most critical component to maximize droplet coverage is the spray nozzle.

Spray nozzle is critical

“The nozzle is actually the working part of the sprayer,” Wolf explained. “It is very inexpensive but the most critical part of the system for droplet size control. Applicators should select the best nozzle to correctly apply pesticides while achieving the exact droplet size recommended on the pesticide product label.”

The correct nozzle also reduces spray drift and provides maximum effective spray quality and droplets. The nozzle atomizes the mixed solution. Generally, large droplets do not provide the best coverage or remain on the plant, but drift less. Smaller droplets have the potential to drift more, especially in higher winds.

Changes in nozzle designs used today began about 30 years ago with a major emphasis on drift reduction. At that time, the extended range flat-fan nozzle was introduced followed by chambered versions of a flat spray nozzle, and now most recently air induction or venturi-style flat fan nozzles. Each design change has resulted in more effective drift reduction.

Cone nozzles, previously prominent in some agricultural spraying settings, are not used much anymore since the fine droplets can result in more drift issues.

“Though useful when first introduced, I don’t recommend the extended range flat fan nozzle anymore,” Wolf said. “In most agricultural settings when the required gallons of pesticide per acre are low, this nozzle is not a good choice because it is more drift prone than the more recent designs. It is best used with application volumes of 10 gallons or more per acre; more commonly used with insecticides and fungicides.”

In field trails, Wolf studied the chambered turbo fan nozzle; an upgraded flat fan nozzle. Due to the chamber design, this nozzle provides good efficacy and less drift potential.

“This is the nozzle type which I generally recommend to applicators for general multi-purpose crop protection applications,” Wolf said.

The latest version of this nozzle is the turbo twinjet fan nozzle with the identical internal design as its predecessor. The nozzle has two exit orifices which change the droplet size to reduce the pressure of the applied droplet. Due to its dual angle spray, this nozzle works well for fungicide application in denser canopies, including treatments for wheat diseases.

The most recent designs are nozzle types utilizing air induction or a venturi. Air is drawn into the nozzle cavity and exits with the fluid reducing drift. This nozzle type is called different names by various manufacturers but for the most part all work the same.

Another new nozzle on the market is the turbo injection or TTI; a combination of the turbo flat fan and the Venturi internal chamber nozzles. The TTI has two chambers and larger droplets. 

“In our droplet measurement tests, this tip has the largest droplets of any tip in the marketplace today. If you are going strictly for drift control then I would suggest this nozzle,” Wolf said.

Wolf concluded his presentation by examining a new concept in pesticide application – calibration of the spray droplet size. The industry is adopting a color-coded, eight-level droplet-size standard developed by the American Society of Agricultural and Biological Engineers.

“Instead of focusing on a numbering scheme for droplet size, we will now focus on categories from extra fine to ultra coarse,” Wolf said. “If a nozzle manufacturer wants to sell a nozzle, they’ll test the nozzle against the standard nozzle set in a lab using a laser beam measuring tool to classify the nozzle into categories based on the orifice size and pressure.”

Chemical companies will provide this droplet category information on product labels as a way to help applicators select and use the nozzle most effectively for crop protection products.

Wolf encourages new and experienced applicators to attend spray application workshops to learn the latest developments in the ever-changing pesticide application field.

“I encourage applicators to attend meetings and tradeshows to find out what’s available,” Wolf said. “Nozzle manufacturers have a pretty good handle on what they are selling. Search them out and talk with them.”

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