Biology Reference
In-Depth Information
you start with a mist nozzle with a small hole at the
beginning of the season, you will soon be deliver-
ing more spray per minute because the hole is
enlarging. This usually means more conspicuous
residue left on the plant as well as more expense.
Hand-Operated Sprayers
“Aerosol bombs” are pressurized sprays in push-
button containers. A gas propellant reduced to
liquid form is added to a pesticide concentrate
and a fine mist is released when the button is
pushed. Unless the container is held 12 to 18
inches away from plants, to allow the gas to
evaporate, there will be some burning (more lit-
erally a freezing) when the liquid gas hits foliage.
Such cans are good for house plants and for spot
treatment of insects outdoors, but air currents
make it difficult to place fungicides effectively.
Aerosols are also used for the application of
wound dressings to trees. (See
Fig. 3
).
Household sprayers of the atomizer type are
intermittent, discharging spray material with
each forward stroke of the pump, or continuous,
maintaining constant pressure. They are too small
and too tiresome to operate for more than a few
plants, and it is hard to get adequate coverage of
underside of foliage.
Compressed air sprayers are adequate for
small gardens and are relatively inexpensive.
Capacity varies from 1 to 6 gallons. They are
meant to be carried slung over one shoulder, but
some come mounted on a cart. Air is compressed
into the tank above the spray liquid by a
hand-operated pump. A short hose, extension
rod, and adjustable nozzle make it possible
to cover undersurfaces. Such sprayers are a bit
hard to pump up, and some models have
carbon dioxide cylinders to provide operating
pressure.
Knapsack sprayers, of 2 to 6 gallons capacity,
are carried on the back of the operator and are
pumped by moving a lever up and down with the
right hand as you spray with the left. These are
more expensive than compressed air sprayers, but
deliver a fine continuous mist and are excellent
for larger gardens.
Figure 3
Pesticide application equipment (Modified
from the National Sprayer and Duster Association)
Slide or trombone sprayers have a telescoping
plunger, operated with two hands. They draw
material from an attached jar or separate pail
and discharge it as a continuous spray. They
develop good pressure and can be used for small
trees, but are tiring to use.
Wheelbarrow sprayers are manually operated
hydraulic sprayers, holding 7 to 18 gallons, that
are mounted on a frame with wheelbarrow-type
handles and one or two wheels. Pressures up to
250 pounds may be developed, providing excel-
lent coverage for shrubs and small trees. This
type works best with two people, one to control
the pump, the other to operate the spray rod.
Hose-end sprayers are attached to the garden
hose so that water supplies the pressure. The
action is that of a siphon. The concentrated
pesticide is placed in a jar, and as water under
pressure is passed over the metering jet a small
amount of chemical is drawn into it. This is a
very easy way to spray, and some models are
relatively accurate in materials discharged. Be
sure to purchase a type with an extension tube
and deflector, so that spray can be directed to
underside of the foliage, with a shut-off at the
jar, not just back at the hose, and with a device
to prevent back-siphonage. Hose-end sprayers
can be used for roses and other shrubs and
for low trees. The droplets may be somewhat
larger than those from a wheelbarrow or
knapsack sprayer, and slightly more chemical
may be used.
