Insecticide Formulations and their Calculation ; A brief Information

Insecticide Formulations and Their Calculation; A brief Information 


An insecticide formulation is a mixture of chemicals (Active + Inert or inactive ingredients) that effectively control a pest population. Formulating an insecticide involves processing it to improve its storage, handling, safety, application, or effectiveness. 

Insecticide formulation is extremely essential for the successful application of any insecticide. Highly concentrated and purified insecticides are not always used. In that form, they are highly poisonous and can kill animals, plants, or even men. 
This is coupled with the fact that much low strength of insecticidal poisons is necessary to kill the insects. Therefore the concentrated poisons are mixed with some agents called Diluents for reasons of safety and economy. The insecticides are sold in the market in the form of formulations.

Few accessory substances are used in formulating a pesticide, such as 

(1) stabilizing agents 
(ii) dispersing agents and emulsifiers 
(iii) wetters 
(iv) spreaders 
(v) stickers and 
(vi) synergists.

The terminology used in Insecticide Formulations;

1) ai – Active ingredient is a part of chemical that is responsible for the pesticidal effect,
2) Inert Ingredient Any substance of pesticide formulation has any pesticidal effect 
3) Carrier- Inert liquid or Solid added to the active ingredient to prepare pesticide formulations
4) Diluent- any liquid or solid material use to dilute the active ingredient
5) Emulsifier – A chemical that aids in suspending one liquid in another
6) Emulsion- A mixture of one liquid to another liquid
7) Wetting Agent – A chemical that causes a liquid to contact surfaces more thoroughly 
8) Suspension – A mixture of fine solid particles in a liquid  
9) Soluble – dissolves in a liquid 
10) Surfactant- increases the emulsifying, dispersing, spreading, and wetting properties of a formulation
Common formulations are listed below:

1. Dry Formulations

These formulations can be used in the dry form only.
(a) Powders
These are ground materials of insecticides, which are used as such without mixing any diluent such as
(1) Powder of Derris roots; 

The roots of D. elliptica possess rotenone, a strong insecticide, and fish poison. also, known as derris powder and tuba root (in Indonesia), it was formerly used as an organic insecticide used to control pests on crops such as peas.

 (2) Powder of Pyrethrum flowers.

Pyrethrum is also the name of a natural insecticide made from the dried flower heads of Chrysanthemum cinerariifolium and Chrysanthemum coccineum. Its active ingredient is pyrethrins.
(b) Dust;
1) Dust is a finely ground material designated by ‘D’.The Particle’s size of dust range between 1 and 400 i.e

2) When an inert diluent is mixed with a small quantity of concentrated poison, then the mixture is called dust.

3) They mostly contain 2%,5%, and 10 % of the poison.

4) The diluent (soapstone, pyrophyllite, lime, or clay) does not react with the ingredient of the poison. 

4) Insecticide dust is especially effective in killing crawling insect pests (bed bugs, roaches, fleas, etc.)

 various grades of dust are prepared  such as
(1) 5% Gammazene 
(ii) 10% Aldrin 
(iii) 2% Folidal etc.

Advantages of  Dust Formulations

Disadvantages of  Dust Formulations

a) Long-lasting

b) they often do not break down

c) Low odor – Easy to apply

d) Not absorbed into surfaces and are readily picked up by pests

e) If spilled, dust can be easily cleaned up

a) Readily become airborne and can contaminate non-target surfaces

 b) Readily inhaled by the applicator, technicians should wear a respirator for application

 c) Can be abrasive, and eye protection should be worn

(c) Granules

The particles of granular insecticides are larger than the particles of dust. The granules vary from 0.25 to 24 mm in diameter. Such insecticides consist of inert material with the poisons absorbed onto them. Granular formulations of certain systemic insecticides are available for the control of leafhoppers. planthoppers, aphids, thrips, etc.


Advantages of  Granular Formulations

Disadvantages of  Granular Formulations

a) Low drift 

b) Ease of application

c) Long residual life outdoors 


a) Water is required to release the insecticide

b) Although some manufacturers are overcoming this aspect

c) Limited to outdoor application

d)Application equipment must be calibrated often

(d) Coated insecticides
Certain stomach cum contact poisons kill the pest through stomach poisoning but they may kill useful insects (predators) also due to contact action. This contact action of such insecticides can be removed by coating them with an inert fine dust so that the poison particles remain coated all over and do not kill useful insects by contact. However, when eaten up by insect pests they kill them by stomach poisoning such as zeilin.
(e) Insecticide-fertiliser mixture
Mostly granular insecticides are mixed in the fertilizers to form an insecticide fertilizer mixture. This mixture can be applied to the plants, will control the soil insects and at the same time, it will provide nutrition to plants. 

2. Formulations for use as Liquid Sprays 

(a) Solutions
Many organic insecticides are not soluble in water but are soluble in organic solvents (amyl acetate, carbon tetrachloride, refined kerosene monochlorobenzene, etc). Solvents also possess some insecticidal properties and are phytotoxic at high concentrations. Therefore it is essential to know that solutions dissolved in solvents are phytotoxic and should not be applied to plants. These solutions can be used against household pests, mosquitoes, and other aquatic insects. 
The advantage is also a solution 
 Form clear liquids for spraying
(b) Emulsifiable concentrates (EC)
This type of formulation is more commonly used. It is a mixture of toxicants; a solvent and an emulsifying agent. In the market, these are available as EC. To spray this insecticide some amount of water is added to make an aqueous suspension. The insecticide when sprayed, the solvent evaporates leaving the toxicant with water. Water also evaporates after some time. More common insecticides of this type are, Endrin 20% EC. Malathion 50% EC etc.

Advantages of  Emulsifiable concentrates (EC)

Disadvantages of  Emulsifiable concentrates (EC)

a) Bind well to fabrics and fibers in the carpet.

 b) Easy to mix and use

 c) Spreads evenly over the foliage

 d) Binds well to soil particles

a) Mild to strong odors

b) Absorption onto porous surfaces

c) Potential burning of plant material

d) Errors in mixing the concentrate with water

e) Some surfaces such as plastic or tile may be damaged

f) Can easily penetrate the skin


(c) Low Volume Concentrate (LVC)
This formulation is termed U.L.V. or L.V.C. because this is not diluted with water but applied as such in a highly concentrated form. Low-volume concentrates are passed through specialized nozzles into a blast of air generated by a blower fan. The air serves as a diluent. This type of formulation is much used for ‘aerial spraying’, for example, L.V.C. of Malathion, L.V.C. of Sevin.
(d) Suspension
This is the formulation in which the active material is suspended as solid particles.
(e) Foam Sprays
The spray mixture of insecticide, when passed through special foam nozzles converts the spray into foam.
(f) Mist Sprays
Sprays with very small droplets are known as mist sprays.
(g) Water-dispersible powder
WDP may contain 15 to 95 percent toxicant. Most of the insecticides are insoluble in water, and are mixed with carriers. These carriers are soluble or partly soluble in water. This mixture of toxicant and carrier is known as W.D.P.

Advantages of  Water dispersible powder (WDP)

Disadvantages of  Water dispersible powder(WDP)

a) No oil-based solvents

 b) Low to no odor

 c) Little hazard of burning plants

 d) Little hazard of penetrating skin

 e) Do not absorb into porous surfaces, when water evaporates

 f) powder sits on the surface and is readily picked up by insects

a) Inhalation of particles while mixing concentrate

b) Constant agitation of suspension prior to and during application

c) Large mesh strainer must be used (>50 mesh) in sprayers

d) Pumps and nozzles can be damaged by abrasion of the particles

e) Visible residues can occur on dark surfacesh

( h) Insecticide Aerosols
Minute particles (0.1 to 50 microns) of insecticide suspended in the air in the form of mist or fog are called insecticide aerosols. Aerosols can be produced by (1) burning (2) vaporizing with heat (3) automizing mechanically or (4) by releasing the insecticide dissolved in liquified gas through a small hole. Released gas evaporates rapidly leaving the toxicant particles suspended in the air. The aerosol bomb is very popular for controlling mosquitoes.

Advantages of  Insecticide Aerosols

Disadvantages of  Insecticide Aerosols

a) Ease of use

b) Ease of storage

c) No dilution or storage of concentrates

a) Expensive

 b) Odor of solvents

c) Atomized droplets are easy to inhale and drift to non-target surfaces


3. Fumigants (Gaseous Formulations)

As described earlier the toxicants in the gaseous form are known as fumigants. These may be used in bins, houses, godowns, ships, aircraft, and soil, etc. Most of the fumigants are inflammable, therefore they are mixed with a non-inflammable gas such as carbon tetrachloride. Some of the common fumigants are listed below. 

(a) Dust Calcium cyanide, sodium cyanide 
(b) Solid Crystals Naphthalene, Paradichlorobenzene 
(c) Liquid Methyl bromide 
(d) Mixture ED/CT mixture:

Advantages of  Fumigants

Disadvantages of  Fumigants

a) Toxic to a wide variety of pests

b) Good penetration of target areas

c) Single treatment will usually kill all pests in the treated area

a) Treated area must be closed or tented to prevent gas from escaping

b) Highly toxic to people


Insecticide Calculation;

            N = TxP/ai
N = Quantity of a formulated Pesticide Required
T = Total Spray Fluid Required
p = Percentage Strength Required
ai = Given percentage strength of a formulated Pesticide 
Example 1; Determine the quantity of Malathion 50 to prepare 100 liters of 0.05%  spray material?
    T=100 lit
     ai= 50
     N=TP/ai = 100×0.05 liters
         =0.1 liter or 100 ml
Example 2; 200 liters of spray fluid contains 700 ml of Malathion 20 EC Determine the percentage strength of the spray fluid?
          N=700 ml
          T= 200 liters= 200000 ml
         P= 700X20

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