Everglades Station Mimeo Report 58*15
Quality of Insecticide Formulations
E. Harris, Jr.*
In purchasing insecticide materials the prospective buyer may have the
tendency to act as if one wettable powder, dust, or liquid concentrate of a
given insecticide were the same as any other wettable powder, dust, or liquid
concentrate of that insecticide. Like any other commodity, insecticide
formulations vary in quality. When used as recommended and for the purpose
intended, the better quality formulations will usually give good results. A
poor quality material will just as likely result in poor insect control, crop
injury, increased labor costs, and/or greater depreciation of application
As an attempt is made to insure that only those insecticide materials of
good quality are used, it should be wise to consider some of the causes of
poor quality among insecticide formulations. It seems apparent that one of
the major causes is the price-cost squeeze. The farmer, like any other busi-
ness man, wants to cut costs by obtaining insecticides at as low a price as
possible. With stiff competition among insecticide dealers the price may
actually be so low that a profit cannot be realized with a high quality
material. Result- the quality of the product is lowered. The grower may lose
far more from crop damage than he saved in purchasing the inferior product.
Usually the basic manufacturer sells insecticides to formulators to be
made into wettable powders, dusts, or liquid concentrates. Many of the insec-
ticide manufacturers issue a formulators' manual describing the methods of
making high quality products. Some insecticide manufacturers do not issue such
a manual. In this situation some formulators may actually not know how to
prepare a good insecticide formulation.
The demand for insecticides in one area of the country may not be as
great as anticipated and so they are shipped to another area. The insecticide
formulation may not be suitable for use on the crops grown in the new area or
it may have deteriorated during storage and shipment. Also, insecticide
materials mixed for non-agricultural use may end up being sold for agricultural
How are we going to recognize the quality product? There are regulations
which require that the amount of actual insecticide in a formulation must be
stated on the label. The State of Florida maintains a service whereby such
products are analyzed to determine if the stated amount of insecticide is pre-
sent. The regulations however apply only to the actual insecticide. Almost
anything can be covered by the labelled terms "inert ingredients" and -'
* Assistant Entomologist.
June 4, 1958
Procedures for testing the quality of insecticide materials may be found
in formulator's handbooks issued by various insecticide companies. Many of
these procedures are tedious and require special equipment but some are easily
adapted for grower use. The procedures listed below are adapted from hand-
books issued by Shell Chemical Corporation and Velsicol Chemical Corporation.
Testing insecticide dust and wettable powders for quality. Much can be
learned by taking a mall quantity of the solid material and spreading it out
on a light colored smooth surface with a knife. Spots or streaks of a
lighter or darker color than the rest of the material will indicate that it
is improperly blended. In field applications of such a material too much
insecticide will be applied in some areas and conversely not enough will be
applied in others. Is there a gritty feeling as the knife is passed over the
material? Grittiness indicates that the material was not thoroughly ground
to a fine enough powder and this condition can result in unequal distribution
of insecticide or undue wear on dusters or spraying equipment. Is this
material lumpy? A lumpy dust will not flow through a duster properly resulting
in uneven distribution of the insecticide over the field. Lumpiness in a
wettable powder will often indicate that it will be difficult to mix with
A factor of prime importance with a wettable powder is how well it mixes
with water. Mix two-thirds of an ounce of the wettable powder with one quart
of water. After mild shaking the material should be well mixed with the water.
Very little of the material should settle out after standing for 30 minutes.
Testing emulsifiable concentrates for quality. Shake up the emulsifiable
concentrate and pour a small quantity into a glass container. Is it clear or
is there a sediment in it? The presence of a sediment may indicate poor
How does the emulsifiable concentrate mix with water? Add two tablespoons
of emulsifiable concentrate to one pint of water. Fill the container and turn
it over several times. The mixture should be immediately and consistently
milky throughout. Let it stand two hours. There should be no clear water or
other clear liquid present at the end of this time. Look especially at the
top of the mixture. Any clear fluid here will probably be the insecticide
solvent and this will burn crops. After standing for 24 hours the emulsion
should again become milky with only mild shaking.
There is a new type of liquid insecticide concentrate now on the market
which is ea~ld e aqueous emulsion or a white flowable emulsion. This material
is white in color so cannot be checked for clearness when in the concentrate
form but otherwise can be tested exactly like the emulsifiable concentrate.
A few test procedures for estimating the quality of insecticide formula-
tions have been discussed. Using these test procedures it is still possible
to obtain a poor quality insecticide formulation but not nearly so probable
as when these test procedures are not used. Thoroughly investigating the
quality of insecticide materials may result in lower operating costs and higher
profit through marketing high quality produce.