Sprayer types used on trees and orchards: how extension services sort them

This page lists the sprayer types that university extension services name for trees, orchards and nurseries, and what each source says marks them apart. It does not say how to use, set up or maintain any sprayer, and it names no makers. Who may apply pesticides is on the pesticide licences guide, and drift and storage rules are on the US pesticide rules guide. Most of the extension material is written for orchards, vineyards and nurseries, and says so.

The types, as the sources sort them

Type	What the source says marks it	Source
Manual hydraulic: hand pump, hand can, backpack	Used mostly for spot treatment and smaller areas.	Ohio State University Extension, FABE-539
Powered backpack (gas or electric)	UNH Extension says manually operated backpacks are most common, that gas-powered models are also made, and that they work differently from manual ones. It also lists air-assist and mist backpack models.	University of New Hampshire Extension
Hydraulic with a vertical boom, no air assist	Built like a field crop boom sprayer turned upright, with higher spray pressure. Ohio State says that even so, its droplets do not effectively penetrate the inner parts of a dense canopy.	Ohio State University Extension, FABE-539
Air-assisted hydraulic (air blast)	A fan directs air at a liquid spray system pointed at the canopy. Ohio State says most vineyard sprayers are in this group and that the air separates leaves so droplets reach deeper. Oregon State calls air blast one of the most common types in specialty crops.	Ohio State FABE-539; Oregon State University Extension, EM 9316
Pneumatic air shear	A low-pressure emitter sits in the exit of a venturi tube and fan air shears the liquid into very fine droplets. Ohio State says this cuts the volume applied per acre but that low humidity, heat and wind then affect it more and add to airborne drift.	Ohio State University Extension, FABE-539
Sensor sprayers	Oregon State names three kinds: standard manually controlled with constant output; sensor sprayers switched on and off by canopy presence at constant output; and canopy adapting sprayers that also change spray volume and air flow in real time.	Oregon State University Extension, PNW 727

Losses the sources put numbers on

Oregon State's PNW 727 says air blast sprayers were first developed in the 1950s, when orchard trees were commonly 20 feet (6 metres) tall or more, and that orchard trees are typically 6.5 to 13 feet (2 to 4 metres). It says losses to the ground of 30 to 50 percent of the spray and off-target drift of 10 to 20 percent are common for air blast sprayers. It says sensor-controlled systems date from the 1980s and were designed to cut labour costs and pesticide waste.

Pumps and nozzles

Oregon State's EM 9316 says the three most common pump types on pesticide sprayers are diaphragm, centrifugal and roller pumps. It describes diaphragm pumps as among the most common, low in maintenance and small for the flow they give. Ohio State says nozzles meter the liquid, set the spray pattern and affect droplet size, and that orchard and vineyard sprayers usually carry hollow cone nozzles. It says flat fan and low-drift cone nozzles are not common in the United States but are becoming as popular as hollow cone in other parts of the world, especially Europe.

What these sources do not cover

The sheets above are written for fruit, nut and ornamental crops, not for climbing or lift-based spraying of street and landscape trees. UNH describes backpack sprayers as inexpensive, lightweight and suited to small jobs on the farm or in the landscape. PNW 727 also carries cost and profit comparisons between sensor sprayer types, which this page does not report. Ohio State says product labels carry requirements such as the application rate and spray droplet size.