AFM 91-19 / TM 5-629 / NAVFAC MO-314
24 May 1989
8-1. General Information. The effectiveness of
through the nozzles. They usually have a pres-
a herbicide depends largely on how well it is
sure regulator, pressure gauge, shutoff valve,
applied, and this, in turn, depends on the
strainers or filters, and chemical-resistant con-
operator and the equipment.
a. Various types of equipment are available
a. Tanks and Agitators.
for applying herbicides (1) wet in sprays or
(1) The trend in sprayers is toward using
mists, (2) dry, in dusts, pellets, or granules, and
corrosion-resistant materials throughout the sys-
(3) as fumigants. An ideal applicator would
tern. Mild steel rusts and flakes off, causing
distribute the herbicide uniformly on foliage, on
delays and poor weed control because of fre-
or in the soil, or in water.
quent nozzle-clogging. Three materials currently
used for spray tanks are stainless steel, alumi-
b. Spraying is the most common application
num, and fiberglass-reinforced plastic (FRP).
method, and may be used for all herbicides
Type 304 stainless steel and FRP resist corrosion
except for some fumigants and aquatic treat-
ments. Spraying not only permits reasonably
by almost all types of agricultural chemicals.
uniform application, but a spray can be directed
Aluminum is vulnerable to attack by some
at a specific area. Sprays may be applied from
sprinkler cans, hand pumps, and compressed-air
(2) Agitation is always desirable to ensure
and power sprayers.
homogeneity of the spray liquid, even if totally
soluble materials are used. The two types of
c. The backpack sprayer is the most popular
agitation are mechanical and hydraulic.
type of hand-operated sprayer. Many backpack
sprayers use compressed air or gas to force the
(a) Mechanical agitation is achieved by a
liquid out of the tank. Others have a pump with
series of paddles on a shaft running horizontally
a hand-lever that is operated with one hand
through the tank, or by means of a propeller on
while the spray wand is held with the other.
one end of the tank. The paddles or propeller
Hand-operated sprayers usually have a tank
are power-driven at low speed. Mechanical agita-
capacity of 3 or 4 gallons, and are most useful
tion is generally used for emulsions with a high
for spraying small, scattered weed patches and
percentage of oil and for wettable powders.
areas that are inaccessible to power equipment.
(b) Hydraulic agitation is accomplished
Backpack sprayers are generally not appropriate
by routing some of the pressurized spray liquid
for very toxic sprays.
back into the tank. The number, size, and
d. Power-driven sprayers range from small,
location of the orifices through which the liquid
wheel-mounted rigs that are useful in turf and
is routed back into the tank depends on the size
gardens, to large field sprayers. Field sprayers
and shape of the tank. Hydraulic agitation is
may be trailer-mounted, truck- or tractor-
most often used for readily soluble or self-
mounted, or self-propelled.
e. Sprayers are classified as low-volume or
(3) All tanks should have a large filler
high-volume, depending on the amount of liquid
opening to facilitate cleaning between uses of
(carrier and herbicide) they normally apply per
unit area. Spray volumes range from 0.1 gallon
b. Nozzles and Tips:
to several hundred gallons per acre. Most weed
(1) Nozzles and nozzle tips are made of
sprayers are of the low-volume type (40 gallons
brass, aluminum, stainless steel, nylon, plastics,
or less per acre). High-volume sprayers are
and rubber. For chemicals that are corrosive or
usually used where vegetation must be saturated.
abrasive, materials harder than brass should be
f. Any water supply line used to fill sprayer
used. Most wettable powders are abrasive, and
tanks should have a backflow prevention device
AMS, for example, is corrosive to brass.
to prevent contamination of the facility water
(2) The nozzle tip converts the spray liquid
into droplets and is thus the most important
component of the sprayer. Nozzle tips should be
8-2. Ground Spraying Equipment. Most spray-
selected to produce the spray pattern best suited
ers consist of a container or tank to hold the
to the particular application. The three basic
spray liquid, some type of nozzle or nozzles to
spray patterns are fan-shaped, cone-shaped, and
direct the spray, and a pump to force the spray