Spray Systems

Counties typically used truck- or trailer-mounted chemical injection (high-end) or tank mix (basic) spray systems. The following is one county’s description of its two spray rigs. These fairly well represent the range of equipment available.

Our high-end unit is a Legacy 6000 chemical injection system from Mid Tech. This unit has a GPS to record the rate, type and amount of chemical used. We download that info to our desktop and print our reports. Our system has three injection pumps with three chemical tanks, and a 300-gallon water tank all on a skid for easy loading and unloading on the pickup. All the controls and the electric start are mounted in the cab on a computer stand. We have three bumper-mounted spray nozzles — 6 ft., 20 ft. and 30 ft. — and a hose reel with 300 ft. of hose in the back. We like this unit because we can easily switch chemicals to spray something else and one person can load and unload everything in less than an hour. A downside of this system — we can only use liquid chemicals, otherwise everything gets plugged up.

Our basic unit can also be loaded in the truck by one person. Just about any chemical can be used because it’s a tank mix system with an agitator in the tank. It has a 200-gallon tank, also on a skid, run by a 5 ½ HP motor. We have two nozzles, a 6 ft. and a 30 ft. on the right-front bumper. There is a hose reel in the back with 200 ft. of hose. There’s no GPS on this system, so we have to keep track of everything. We mounted switches in the cab to run the nozzles, but we have to get out to turn the system on and off.

Another type of truck-mounted spray system used in roadsides is an invert emulsion sprayer. Invert emulsion was developed to reduce herbicide drift and volatilization by producing large droplets of water surrounded by oil. The mayonnaise-textured droplets do not dry as fast as water, so leaf penetration is improved. Invert emulsion sprayers do not work with all types of chemical products; liquid formulations usually work best.