Biology Reference
In-Depth Information
Applying The Chemicals
Spraying is the application of a chemical to
a plant in liquid form; dusting the application of
a fine dry powder. The difference between
spraying and dusting was very clear-cut before
aerosol bombs, mist blowers, and fog machines
were developed to apply liquids in such concen-
trated form that the particles are practically dry
before they reach the plant and before spray-
dusters were made to deliver wetted dusts.
Sprayers vary from a flit gun or pint atomizer,
which takes an hour to discharge a gallon, to
power apparatus that discharges 60 gallons a
minute at 800 pounds pressure from a 600-gallon
spray tank. Dusters vary from the small
cardboard or plastic carton in which the dust is
purchased to helicopters. Applicators for pressur-
ize sprays or aerosols vary from the one-pound
“bomb” to truck-mounted fog generators or air
blast machines. See
Fig. 1
for various applicators.
and also in order to see the distribution of the
concentrates, they often have to be used at night.
They are not too efficient for very tall trees, and
the droplet size has to be rather carefully regu-
lated. Too large drops may fall out before they
reach a tree, and too small drops may not settle
down but go on past.
Although we usually think of mist blowers on
trucks for large scale operations, there are now
some about the size of knapsack sprayers that,
engine and all, are worn on the back around the
garden. They weigh around 35 pounds and will
cover foliage up to 30 feet. They cost, however,
somewhat more than the hydraulic power
sprayers of small estate size.
Hydraulic Sprayers
Mist blowers will probably never entirely out-
mode hydraulic sprayers, which can place the
spray more accurately, at a greater height, and
can operate under more unfavorable weather con-
ditions. For trees, high gallonage per minute and
enough pressure to drive sprays high in the air
have advantages, but for garden plants the
emphasis should be on cutting down gallonage
and pressure.
Power sprayers for home gardens are available
in almost any size, from 5-gallon capacity on up,
and may have gasoline or electric motors
(see
Fig. 2
). For the orchard a spray gun is
Mist Sprayers
In orchards and in shade tree work there has been
increasing use of mist blowers, air blast machines
that carry droplets of concentrated pesticides to
plants in air rather than water. They are speedier
than hydraulic sprayers, use far less water, which
may be scarce in times of drought, and do not
leave puddles or poisonous run-off which may be
dangerous to pets and birds. They cannot, how-
ever, be operated in much wind; for that reason,
