A successful Mountain, Pine, Ips, Spruce or other bark beetle pesticide application program has four objectives; diagnosis of the problem, the right chemical and rate, proper timing, and thorough coverage. These are essential and cannot be overemphasized. Any one component is worthless without all the others. Often a pest is correctly identified and the right chemical chosen but the spray application does not provide thorough coverage.

Thorough coverage is probably the most difficult objective. Weather, size of trees, and available spray equipment all influence application. Weather conditions and tree size are beyond control, but you can select a pesticide applicator with the proper equipment to meet your needs. Repeated applications although preferred, are sometimes uneconomical. Therefore, you must choose an applicator with equipment that gets the job done right, the first time.

Types of Pine & Spruce tree sprayers

A hydraulic (liquid) sprayer uses water as a diluent and carrier. The pressure developed from the pump is used to atomize the spray mix at the nozzle and deliver it to the target. An air-blast sprayer uses water as a diluent and both air and water as a carrier. Pressure from the pump provides atomization and a high-velocity air stream carries the droplets to the target.

High Volume High Pressure (HVHP) 35 to 60-gpm @ 600 to 800-psi pesticide application technology has proven itself as the most effective means in combating invading beetles, with other technologies providing varying degrees of success.

Important Note:
Recent studies conducted by the US Forest Service have shown the use of Micro-injection as a means of pesticide application as being an ineffective control in stopping the spread and infestation of Mountain, Pine, Ips, Spruce and other bark beetles.

Horizon Forestry™ utilizes multiple pesticide application technologies and capabilities including:

Hydraulic tree sprayers

Hydraulic (liquid) sprayers are used for all sizes of trees. Tree sprayers are available as trailer models to be towed or skid-mounted models for use on pickup trucks or other vehicles.

They vary in size from a 2.5 to 10-gpm pumps and 2 to 20-hp engine Low Volume Low Pressure (LVLP) units used by homeowners to 15 to 60-gpm pumps and and 35 to 65-HP engine High Volume High Pressure (HVHP) machines used by municipalities, institutions, or custom-spray operators like Horizon Forestry™.

Tank sizes vary from 10 gallons up to 1,000 gallons. Some of the large trailer units can be powered from a tractor power-take-off shaft. Between these extremes there is a wide range of sizes and options.

The hydraulic sprayer uses large volumes of water and high pressure. The taller the tree, the higher the required pressure. However, since higher pressures tend to produce smaller droplets, larger orifices must be used to offset this effect. Droplets must be relatively large to have sufficient momentum to carry to the tree tops and to adhere to the surfaces. These factors are documented in the table of guidelines below.

Minimum Hydraulic Sprayer Requirements* for various tree heights;

Trees up to 15', 3-gpm, 400-psi, (LVLP)
Trees up to 25', 5-gpm, 400-psi, (LVLP)
Trees 20' - 30', 10-gpm, 400-psi, (LVLP)
Trees 30' - 45', 15-gpm, 400-psi, (HVLP)
Trees 35' - 50', 20-gpm, 400-psi, (HVLP)
Trees 45' - 65', 20-gpm, 800-psi, (HVHP)
Trees 65' - 85', 35-gpm, 800-psi, (HVHP)
Trees 85' - 115', 60-gpm, 800-psi, (HVHP)

* Pennsylvania State University College of Agriculture

As the tree height increases, the spray angle at the nozzle is decreased to concentrate the pressure in the spray stream. In spraying tall trees, a solid stream may be used with most of the liquid breakup being produced by the resistance of the air after the liquid leaves the gun.

Nearly all hydraulic tree sprayers use a hand-held gun. For short trees and shrubs a multiple-outlet gun may be used but the single-outlet gun with a pistol-grip valve is the most common. Many applicators use a variable discharge-angle gun; with a twist of the handle the spray angle can be controlled from a wide angle for short trees and shrubs to a solid stream for tall trees.

The working pressure at the gun is very important for satisfactory operation. Often the gun is a considerable distance from the pump. Runs of 200 feet or more are common where the sprayer must be parked away from the tree being treated, i.e. street parking when spraying a backyard tree for a homeowner. Whenever liquid flows through a hose, friction loss is unavoidable. However, this loss can be minimized by choosing the proper diameter hose for the desired flow rate. Of course the choice is a compromise among friction loss, cost, and handling ease (size and weight of hose with water).

Since friction (pressure) loss is directly proportional to length, you can extend the information to any length, i.e. a 100-foot hose has twice the loss of a 50-foot hose. Select hose size based on flow of the gun or other delivery means being used, not the rated pump capacity. It is interesting to note that for a given flow, a change of one commercial hose size has a big effect on friction.

Additional pressure losses occur at fittings, valves, and turns. To check pressure at a gun, simply 'tee' a gauge into the line at the gun and read pressure while spraying at the desired rate. No friction loss occurs when the gun is off because there is no flow present. As you start spraying, you may observe a quick pressure drop at the gun; this drop is the friction loss in the hose as the flow initiates.

Generally, coverage by a hydraulic sprayer is relatively good with a high volume of water; if there are problem areas, they are usually in the tops of very tall trees. Height of effective coverage can be increased by using elevated truck-mounted platforms, gun extensions, or ladders.

The spray mix is relatively dilute and therefore relatively safe. Although the droplets are larger and more resistant to drift than those from an air-blast sprayer, drift can still be a serious problem. To insure adequate coverage, trees are usually sprayed to the point of runoff.

FMC Rotomist® & Air-blast (Mist Blower) sprayers

The air-blast (mist-blower) sprayer applies a concentrated pesticide mixture using a high-velocity, large-volume airstream. Since air is the carrier, the air-blast sprayer uses only a fraction of the water used by hydraulic units. With air providing the transport energy, the droplets must be relatively small. To accomplish this, air-blast sprayers are usually equipped with cone nozzles. If the air velocity is greater than droplet velocity at the point of injection, additional atomization takes place.

The small droplets give the necessary coverage for good disease and insect control. Although small droplets are desired for good transport and coverage, they must be large enough to deposit on the foliage. This balance between size and deposit establishes a minimum volume per area rate. Research has shown that more spray volume should be directed toward the top of the tree than the lower portions to obtain uniform coverage. The larger droplets, containing most of the spray volume, settle out of the air stream very rapidly.

The larger air-blast sprayers have capacities up to 20 gallons per minute. The combination of engine size, fan size, and type of air tunnel allow some sprayers to reach trees 80 feet tall.

Competent operation is essential when using air-blast sprayers since the spray pattern is almost invisible. It is also impossible to determine the extent of coverage since there is no runoff. Trees to be sprayed must be directly accessible to the sprayer unit because best coverage and distribution is obtained by spraying up through the canopy. If the distance from the tree to the sprayer is too great, the velocity will be insufficient to penetrate the canopy.

Most airstreams lose 75 percent of their velocity in the first 25 feet after leaving the sprayer. Therefore, the sprayer should be immediately adjacent to the tree.

Two factors affecting the coverage obtained with air-blast sprayers are airstream velocity and volume. In addition to canopy penetration, velocity is important in getting the spray to the top of tall trees.

Spray material must be forced into the foliage with a turbulent force. To achieve this, air velocity is nearly 100 mph when leaving the sprayer, and must be at least 15 mph at the tree surfaces.

Generally, increasing the volume of air applied improves the spray distribution. The blower must displace the volume of air in the tree with air from the sprayer containing spray droplets. When the available energy is fixed, the higher the ratio of volume to velocity, the better the distribution.

Air-blast sprayers are not trouble free. In addition to wind conditions, a potential problem during cold weather is freezing of the spray droplets both on the nozzles and while air-borne. Evaporative cooling may cause ice to accumulate on the nozzles. This can alter the droplet size as well as the distribution patterns. Also, sometimes after leaving the nozzle droplets will form ice crystals and coverage is negligible. To avoid freezing problems, air-blast spraying should be done only when the temperature is above 45 degrees Fahrenheit.

Although air sprayers can reach tall trees, their energy consumption far exceeds that of hydraulic sprayers. The energy need is greater because air-blast sprayers must move both air and liquid. Some air sprayers require as much as a 140-HP engine.

On the other hand, air sprayers cover trees faster and require less refilling, than hydraulic sprayers. When spraying large numbers of trees, timely operation can result in pest control equal to hydraulic sprayers, with lower overall costs.

Horizon Forestry™ is Colorado's only commercial applicator to utilize the rugged all-terrain capabilities of the Mercedes Unimog. With it's unique capabilities we can move our equipment through areas previously unreachable by conventional 4x4 trucks and pickups.

Horizon Forestry™ can provide cost effective and competitive beetle management solutions for individuals, homeowner's associations, resorts, ski areas and ranches as well as local, state and federal governmental agencies.