Active ingredients are mixed with other ingredients to increase the
efficiency and ease of application, prolong the period of effectiveness
or reduce the damaging effects on plants and man. The whole product
(formulation) in its bottle or packet is given a trade name, which often
differs from the name of the active ingredient. The main formulations
are as follows:
- Liquids (emulsifiable concentrates) contain a light oil or paraffin base
in which the active ingredient is dissolved. Detergent-like substances
(emulsifiers) present in the concentrate enable a stable emulsion
to be produced when the formulation is diluted with water. In this
way, the correct concentration is achieved throughout the spraying
operation. Long chain molecular compounds (wetter/spreaders) in
the formulation help to stick the active ingredients onto the leaf after
spraying, particularly on smooth, waxy leaves such as cabbage.
- Wettable powders containing extremely small particles of active
ingredient and wetting agents form a stable suspension for only a
short period of time when diluted in the spray tank. Continuous
stirring or shaking of the diluted formulation is thus required. An
inert filler of clay-like material is usually present in the formulation
to ease the original grinding of particles, and also to help increase the
shelf life of the product. It is suggested that this formulation is mixed
to a thin paste before pouring through the filter of the sprayer. This
prevents the formation of lumps that may block the nozzles.
- Dusts are applied dry to leaves or soil, and thus require less precision
in grinding of the constituent particles and less wetting agent.
- Seed dressings protect the seed and seedling against pests and
diseases. A low percentage of active ingredient, such as iprodione applied in an inert clay-like filler or liquid reduces the risk of
chemical damage to the delicate germinating seed.
- Baits contain attractant ingredients, e.g. bran and sugar, mixed with
the active ingredient, e.g. methiocarb, both of which are eaten by the
pest, such as slugs.
- Granules formulated to a size of about 1.0 mm contain inert filler,
such as pumice or charcoal, onto which the active ingredient is coated.
Granules may act as soil sterilants (e.g. dazomet), residual soil
herbicide (e.g. dichlobenil), residual insecticide (e.g. chlorpyrifos),
or broad-spectrum soil nematicide and insecticide (e.g. aldicarb).
Granular formulations normally present fewer hazards to the operator
and fewer spray-drift problems.
Labels on commercial formulations give details of the active ingredient
contained in the product. Application rates for different crops are
included. DEFRA approves pesticide products for effectiveness.
(or plant damage) may occur when pesticides are
unthinkingly applied to plants. Soil applied insecticides, such as aldicarb
, can cause pot plants, such as begonias, to go yellow if used
at more than the recommended rate. Plants growing in greenhouses are
more susceptible because their leaf cuticle is thinner than plants growing
at cooler temperatures. Careful examination of the pesticide (particularly
herbicide) packet labels often prevents this form of damage.