🧴 Pesticide Formulations
Major pesticide formulation types, components, and their role in safe and effective field application.
Pesticide formulations determine how active ingredients are delivered safely and effectively in the field. This lesson covers major formulation classes, their composition, and practical manufacturing concepts.
21.PESTICIDE FORMULATIONS
Pesticides are formulated to make their application easier and to improve their
effectiveness under field conditions. Formulation also improve the properties, storage,
handling and safety.
Formulation is the process by which the active ingredients are made ready to be
used by mixing with liquid or dry diluents by grinding or by addition of emulsifiers,
stabilizers and other formulation adjuvant to form a commercial product.
Classification of Formulations
a) Dry formulations
Dusts
Wetable Powders
Crannels
Seed disinfections
Others
b) Liquid Formulations
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Emulsion concentrates
-
Oil concertrates
-
Others
c) Others
A) DUSTS
Dusts consist of a mechanical mixture of the active ingredients with or without an
inert diluent pulverized to a particle size of 3 to 30 µ. Dusts can be classified as follows:
-
Undiluted toxic agent (sodium fluoride)
-
Toxic agent with an active diluent (rotenone with sulphur)
-
Toxic agent with an inert diluent (DDT with pyrophyllite)
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Inert dusts (silica)
Insecticides like calcium arsenate, sodium fluoride ground pyrethrum flowers may
be applied as dusts with diluent.
Others like rotenone can be mixed with insectides like sulphur and applied.
Others may be diluted with inert materials like talc in order to cover more area and also
to reduce the phytotoxicity of the chemical or to improve the chemical or physical
properties.
When inert materials like silica, saw dust, ash are used they may cause
abrasions on the pest surface or absorb moisture and desiccate them.
Method of Manufacture
Two methods are employed
-
Ball Mill Method
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Solvent Mix Method / Toxicity Spray Method
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Ball Mix Method
In this method the ingredients viz., the active ingredients and fillers like soap
stones, talc or pyrophyllite are intimately ground in a Ball Mill and mixed together by the
blending operations of a mechanical mixture. In the grinding process, heat develops and
increase the temperature, which melts the pesticide and thus gives a fine coating on the
inert material. Also in the grinding process the pesticide particles get distributed among
the diluents. Consequently grinding of the active ingredient together with the diluent
gives a more efficient formulation than separate grinding of the ingredients with
subsequent mixing. The finer the grinding more effective is the dust. However lumps
may be formed in this process and these lumps are broken into fine particles by means
of a powerful jet of air introduced from the sides. Particles of certain size alone are
taken upstream by the jet of air and those heavier than the limit prescribed fall back in
the ball mill to be ground again.
- Solvent Mix Method/Toxicant Spray method
The toxicant in the form of a liquid is sprayed into the dust mixture during the
blending the blending process. The solvent may be allowed to evaporate or it may be a
higher boiling solvent of a petroleum fraction.
- Bulk Density
It depends upon particle size, shape and actual density. It is an indication of
fluffiness. A good diluent is one which weights 300-450 kg/m [3] (0.3 g/cc). Lighter
materials have low carrying power and remain in the air for a longer time. Heavier
materials fall rapidly.
- Particle Density
Particle density is the actual density of the solid materials, only as if there were
no air spaces between them. It affects the feeding in the duster. Carrying power
segregation and settling of dust depend upon particle density.
- Electrostatic Charge
It is produced due to the friction between particles and the dusting equipment.
Materials with high silica give type charge to the blower and recharge to the dust steam.
Electrostatic charges on particles affect the attraction of dusts to the plant surfaces and
dust distribution.
- Flowability
It indicates the feed rate of dusting equipment. The angle of slope which is a
measure of flowability is measured by allowing the dust to fall through a funnel upon
disc. Greater the angle poorer is the flowability. Dust with fibrous or needle shaped
particles have a slower feed rate than dusts with spherical particles.
- Other Properties
a) Hardnes -causes abrasikon of the equipment
b) Absorption -affects caking
c) Asorption -tendency to form lumps
Though dusting is less effective compared to spraying it is suitable in areas of
water scarcity. Usually 10-50 kg is applied.
Summary Cheat Sheet
| Topic | Key exam point |
|---|---|
| Main topic | Pesticide formulations |
| Common types | EC, WP, SP, granules, dusts, and suspension concentrates |
| Formulation meaning | Commercial preparation containing active ingredient plus carrier/adjuvants |
| Dusts | Solid formulation with low active ingredient concentration applied directly |
| Granules | Coarse particles used for soil or special placement applications |
| EC meaning | Emulsifiable concentrate that forms emulsion in water |
| WP meaning | Wettable powder dispersed in water for spray use |
| Purpose of formulation | Improves handling, stability, application, and safety of active ingredient |
| Exam distinction | Formulation type and active ingredient are separate things |
| Trap | Do not confuse EC with SC or WP; each has different physical behavior in water |
References
3 sources • [1] [2] [3]
References
Principles of Soil Science and Agricultural Chemistry — Standard BSc Agriculture Textbook
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