Using the same sprayer equipment for weed control and
then for insect control is neither safe nor desirable. No matter
how well a tank is rinsed after use of a herbicide, a residue will
be left in the tank and in the gaskets, hoses and parts. If the
same tank is then used with an insecticide to spray a plant, it is
possible to kill the plant with the herbicide left in the tank.
The wisest policy is to maintain two sprayers, one for herbicides
and another for insecticides and fungicides. Have them clearly
labeled according to use. Always wash after each use.
Pesticide application equipment comes in all shapes,
sizes, types, and prices. Select equipment according to common
Proportioner or Hose-End Sprayer:
These inexpensive small sprayers are designed to be attached to a
garden hose. A small amount of pesticide is mixed with water,
usually no more than a pint, and placed in the receptacle attached
to the hose. A tube connects this concentrate to the opening of
the hose. When the water is turned on, the suction created by the
water passing over the top of the tube pulls the pesticide
concentrate up and into the stream of hose water. The stream can
reach into medium-high trees if water pressure is high. Problems
are encountered from poor spray distribution and clogging of
nozzles. The metering out of the concentrate into the stream of
hose water is very inaccurate, since it is determined by the water
pressure. Proportioners put out an excessively high volume of
spray for most needs, using excessive pesticide. These sprayers
are popular due to low cost, but the low purchase price is quickly
negated by the cost of excessive pesticides used. All hose-end
proportioners should be equipped with an antisiphon device to
prevent back-siphoning of toxic chemicals into the water system.
The trombone sprayer is a medium-sized, hand-held piece of
equipment. A spray mixture in the correct dilution is prepared in
a container such as a bucket. The intake tube of the sprayer is
inserted into the mixture in the bucket. Pump pressure is created
by operating the sprayer in a trombone-like motion. The pesticide
is pulled up the hose and out the end of the sprayer. A uniform
concentration of the spray can be maintained, since the pesticide
is mixed with a known quantity of water. When using a wettable
powder, agitate the spray mixture frequently to keep it in
suspension. Trombone sprayers are excellent for spraying trees and
shrubs, are easy to wash and keep clean, but require some effort
Compressed Air Sprayer (backpack or tank sprayer):
Spray is mixed in a small tank (generally 1 to 5 gallons) and the
tank is carried over the shoulders. A hand-operated pump supplies
pressure during application. A uniform concentration spray can be
maintained since the pesticide is mixed with a known quantity of
water. Frequent agitation of the spray mixture is necessary when
using a wettable powder formulation. Applicator has excellent
control over coverage, making this sprayer a good choice for
treating dwarf fruit trees, vegetables, and ornamentals. Spray
will not reach into tall trees. As water weighs approximately 8.23
pounds per gallon, small tanks are easier to use than large tanks.
Small Power Sprayers:
These have the advantage of being motor-driven, so the operator
does not have to stop to pump up the tank. They are lightweight,
since the spray in the tank is concentrated and diluted with air
as it is sprayed. Power sprayers provide uniform pressure, but are
generally too expensive for home garden use.
The duster may consist of a squeeze tube or shaker, a plunger
that slides through a tube, or a fan powered by a hand crank.
Uniform coverage of foliage is difficult to achieve with many
dusters. Dusts are more subject to drift than liquid formulations
due to their light weight and poor sticking qualities.
The usual approach consumers use when applying a
pesticide over a given area is to mix a tablespoon or two of a
certain pesticide and apply it to a problem area. This is
acceptable if the label gives recommended rates in teaspoons or
tablespoons per gallon. But some pesticides, specifically
herbicides and insecticides for lawns, do not give rates in
tablespoons or teaspoons per gallon. Instead, they give rates of
application in teaspoons or tablespoons per 100 or 500 square
feet. Unfortunately, the consumer all too often solves this
problem by guessing how much to use. This can be dangerous; too
concentrated may be too toxic; too little will not control the
problem. It is irresponsible of the consumer to apply chemicals at
improper rates. It is dangerous to him/herself, neighbors, and the
A better approach is to calibrate the sprayer. The
calibration of a home sprayer is relatively easy. Once it has been
done, it has been done for the life of the sprayer, provided the
nozzle remains unchanged, clean, and adequate pressure is used. It
must be kept in mind that the rate at which the liquid is applied
varies with the pressure and size of the opening in the nozzle.
High pressure and a large opening in the nozzle permit more liquid
to be applied over a given area than low pressure and/or smaller
nozzle. For calibrating a sprayer, the procedure is as follows:
1) Fully pressurize the sprayer and determine delivery
time. This is done by spraying water through the sprayer to fill a
pint jar while noting the time needed to do so. Mark this delivery
time on the sprayer for future use.
2) Calculate the area to be treated. Measure the area
that is to be sprayed. Multiply length times width to determine
the area of a rectangle. The area of a triangle is calculated by
multiplying the base times the height and dividing by 2. Most
areas can be calculated by combining rectangles and triangles or
subtracting triangles from rectangles.
3) If the area is large, divide it into sections equal
to the size of the delivery area.
Spray an area with water, at normal working speed, for
30 seconds. Measure the area sprayed. This tells how much area can
be sprayed in 30 seconds and therefore the amount that is applied
over that area (see item 1). For example, assuming that it has
been established: 30 seconds of spraying delivers a cup and 30
seconds of spraying will cover 100 square feet; then 1000 square
feet require 5 cups spray (5 x 10) delivered or, 1 quart + 1 cup
or 40 ounces. If the label calls for 3 tablespoons of pesticide
for 1000 square feet, then, 3 tablespoons of pesticide must be
mixed with 40 ounces of water to achieve proper spray coverage.
Many commercial-type chemicals are given in pounds to the acre or
quarts to 100 gallons of water. To convert rates to equivalents
used by a consumer, consult the pesticide conversion chart at the
end of this chapter.
Either compressed-air sprayers or hose-end sprayers can
be used. Hose-end sprayers do not meter out the pesticide as
evenly as compressed-air sprayers. However, compressed-air
sprayers do not maintain pressure as evenly as hose-end sprayers
unless frequently pumped. Some hose-end sprayers will not continue
to spray pesticide if the thumb hole is not covered. Other
hose-end sprayers use a trigger device to control the spraying.
The spray pattern best used to cover an area of ground
is one which will give uniform coverage with little spray overlap.
Overlap can be a problem, causing certain areas to end up with an
extra dose of pesticide. The spray pattern used to apply the
pesticide should be continuous and uninterrupted. If a herbicide
is being applied, the sprayer should not be slowed down or stopped
at each weed. If the herbicide has been mixed correctly and the
sprayer is properly calibrated, the continuous uninterrupted flow
of chemical will be sufficient for good pest control. The spray
pattern should be directed so that the applicator does not walk
through it while spraying. The spray pattern should form an arc no
more than 3 to 4 feet on either side of the operator. The sprayed
area should have a small amount of overlap to ensure coverage.
There can be a time when overlap may be beneficial. If good spray
coverage is questionable such as when using hose end sprayers, cut
the application rate in half and apply the pesticide first in an
east-west pattern, then in a north-south direction. This gives
better coverage with devices typically poor in their metering
When the mixture on the label is in teaspoons or
tablespoons per gallon and the plants are upright such as shade
trees, fruit trees, shrubs, and vegetables, spray the leaves until
pesticide solution drips from the leaves. Dont forget to
spray the underside of leaves for good coverage.
Spray Pattern with a Single Application
Spray Pattern with a Double Application
When applying pesticides, wear the protective clothing
and equipment the label recommends. To prevent spillage of
chemicals, always check application equipment for leaking hoses or
connections and plugged, worn, or dripping nozzles before adding
pesticide. Before spraying, clear all people, pets, and livestock
from the area. To minimize drift, apply pesticides only on days
with no breezes. If moderate winds come up while you are working,
stop immediately. Reduce drift by spraying at a low pressure and
using a large nozzle opening. Generally, the safest time of day to
spray to reduce the hazard of drift is early morning. Vaporization
is the evaporation of an active ingredient during or after
application. Pesticide vapors can cause injury. High temperatures
increase vaporization. Choose pesticide formulations that do not
evaporate easily, and spray during the cool part of the day to
reduce vaporization. Some products, like 2,4-D, are very volatile
and can move for miles under favorable conditions. They should not
be used near highly sensitive plants like grapes and tomatoes. Do
not apply when it is windy nor when temperatures following
application will reach above 85 degrees F.
Thoroughly clean all equipment immediately after use.
Pesticides should not be stored mixed. If you have excess
pesticide mixed which cannot be used, spray it over an area that
it will not harm. Check the pesticide label to determine safe
areas. Thoroughly clean all spray equipment inside and out with
clean water. Dont forget to flush the hoses and nozzles. Be
careful that the cleaning water does not damage crops. Do not dump
the rinse water in one place where it will be concentrated and may
become a pollutant. Spray the rinse water over a broad area so
that the pesticide will be further diluted. Never rinse
pesticides down the drain!
To clean 2,4-D type herbicides from hand spray
equipment such as a 3-gallon garden sprayer, use household
ammonia. Thoroughly rinse the equipment with fresh water after
spraying. Fill the spray equipment with an ammonia solution, using
one cup of ammonia to 3 gallons of water. Let the equipment soak
for 18 to 24 hours.
Always spray part of this mixture through the pump,
hose, and nozzles at the beginning and end of the soaking period.
NOTE: 2,4-D cannot be completely removed from a sprayer once used
in it. Do not use this sprayer to apply other pesticides
to desirable plants.
Storage and Disposal
Gardeners should store all pesticides in their original
containers, in a locked cabinet. No exceptions if you are
concerned about children's lives! They should be protected
from temperature extremes, some can be damaged upon freezing,
others can be altered by heat. Do not store pesticides in the
home! Empty containers are best placed in refuse cans destined for
a sanitary landfill. Wrap containers in newspaper and secure
before disposal. Some counties have special chemical dumps for
pesticides. The bottle should be rinsed out first, pouring the
rinse water into the spray tank. Rinse three times, allowing 30
seconds to drain between each rinse. Never use empty pesticide
containers for other uses, never allow children to play with empty
containers. If possible, break the containers or punch a hole
through the bottom before disposal. Do not burn paper containers.