PESTICIDES LABELLING METHODS and THEIR QUANTITY CALCULATIONS

Pesticides labelling is done by manufacturers in a manner to convey information to the users about their specific products. Based on labeling,  quantity calculations for selected pesticide are carried out.

Pesticide is an umbrella term for chemical formulations, which include insecticides, fungicides, herbicides, rodenticides, wood preservatives, gardening and household disinfectants.  Each chemical is meant to eliminate or weaken a particular class of pests and vectors which may affect our agriculture, horticulture, animals and household.

Readers of this article may also like to also go through my earlier article Pesticides.  This article describes types of pesticides and the way they work to get rid of intended insects, pests etc.

This article is in two parts: 

1. What do the various numbers and symbols in the Label mean.
2. How to carry out quantity calculations of pesticide for particular requirement.

This article does not deal with what pesticide needs to be used for a particular infestation. I hope to cover same in my next post.

Part One:   What do the various numbers and symbols in the Label mean:

Commonly the pesticides labelling on the package would have the following information printed on it:

1. Active Ingredient (a.i.) : this would indicate the particular chemical used.
2. Formulation: would specify type of formulation e.g. whether in dry form or liquid form. Then there are further subdivisions as shown below. The product could be a mix of two or more chemicals also.
3. Concentration of formulation: would be given as quantity of a.i. in a given volume.
4. Hazard: Class I a = extremely hazardous; Class I b = highly hazardous; Class II = moderately hazardous; Class III = slightly hazardous and Class IV = unlikely to present any acute hazard in normal use.
5. Product Name
6. Company name

Common Abbreviations for types of formulations:

Manufacturers provide the active ingredients in various forms of formulation so as to provide a lot of flexibility to users as per their need and convenience.

How to decide on type of ingredient and its specific formulation :

1. Suitability of the pesticide ingredient for the type of pests. The label would provide this information.
2. Is the life stage of the insect or weed within the effective range of the product? Some insecticides may target specific insect life stages (for example, grubs or the immature stage of a beetle), while herbicides may target specific plant growth stages.
3. Suitability and ease of using the particular formulation of pesticide.
4. Restrictions on application of the pesticide. For example, Pesticides for food crops need to be applied before a certain number of days before harvest, as specified by the label. Often indoor foggers require vacating the building for a specific amount of time. Must read the label thoroughly.
5. Availability of application equipment and personal protective equipment as listed on the label. Ready-to-use products may be considered also which eliminate the measuring and mixing requirements of concentrated products. These products also eliminate need for personal protective equipment or other mixing and application equipment.
6. Whether products required for smaller area, for larger area or protected Purchase only the needed amount for particular period. Reduces storage needs. Pesticides stored over longer time periods tend to lose effectiveness.
7. Decide whether pesticides has to offer a short period of control or long-term protection depending best for your situation.

Representative illustration

Below is given specs as provided by manufacturer for Imidacloprid in three formulations type – G granules, F flowable and WSP water soluble powder and respective a.i. present. The type and strength are indicated.

Part Two: How to carry out quantity calculations of pesticide.

The manufacturers of any particular pesticide formulation also provide other information, besides those covered in Part One, such as :

1. Purpose i.e. against which pest(s) it is meant to be used.
2. Rate of application.
3. Compatibility with other pesticides and/or fertilizer.
4. Conditions in which to be used. Whether to be used before flowering or not.
5. Protective gear to be used.

Once farmer user  has decided on a particular pesticide based on above, the question arises as to the amount to be used for his particular requirement.

Typically there are four ways we can carry out quantity calculations for the correct amount of pesticides.

1. Amount of active ingredient (pure chemical) needed per hectare or acre. Recommendation might be to use 2 kg active ingredient (a.i.) of X pesticide per hectare i.e. 2 kgs. of pure (100%) X.
2. Amount of actual formulation needed per hectare or acre. Recommendation is for 4 liters of Y 50% EC per hectare or another one for 2.5 lbs. of Y 80% WP per acre. Here two calculations are required. One how much formulation needed. Two how much water is required to cover entire area.
3. Amount of actual formulation needed per liter or gallon of water. Recommended to use 5 cc of Z 50% EC per liter of water or 2 tablespoons of Z 80% WP per gallon of water.
4. Percentage concentration of formulation in the spray water. Recommended concentration of pesticide in the spray water is given in terms of percent by weight or volume rather than cc/ liter or tablespoons/gallon.

Consider use 1 and 2 type of method of calculation for large plots. Calibration may need to be done for the spray equipment for accurate dosage of pesticide to be disbursed,

Use is made of 3 and 4 type of method of calculation for general type suited to smaller plots or for lesser accuracy,

How to Calculate Formulae.

Here I am using X, Y, Z in place of actual names of pesticides for simplicity.

Calculation for active ingredient basis

1. For solid formulations (WP’s, EC’s, G’s)

Kg/ha or lbs/acre actual formulation = (amount of a.i. recommended (kg/ha,

lbs/acre))  /  (%a.i. in formulation)

Example: A recommendation for aphids calls for using X at 2 kg active ingredient/hectare. How much X 40% WP would be needed per hectare?

Solution:  Required amount    =       2 kg / 40%  =  5 kg/ha

         2.  For liquid formulations (EC’s)

Liters/ha  = (kg/ha of a.i. recommended)  /  (% a.i. EC)               OR

Liters/ha of EC needed =  (kg/ha of recommemded a.i.  x 1000) /  (gms of a.i. per

liter of EC)

Example: How much Y 20% EC would be needed per hectare if a recommendation for mites calls for 0.2 kg a.i. Y per hectare?

Solution:           Liters of 20% EC needed = 0.2 kg / 20%  =  1 liter

Calculation for actual formulation needed, given dosage per hectare or acre.

Hectare basis

Amt needed = (amt of formulation needed/ha ) x (area sq.m.) / (10000)

Acre basis

Amt needed  =  (amt of formulation / acre) X (area sq. ft)  /  (44000)

Example: recommend applying Z 2.5% strength granules broadcast at 120 kg/ha for controlling A insects in maize. If the  field measures 40 x 40 meters, how much Z will be needed?

Solution:  Amt needed =  120 x 1600 sq.m. /10000 = 19.2 kg

Percentage strength spray recommendation.

Determine first whether the spray’s percentage strengths to be calculated in terms of active ingredient or in terms of actual formulation.

Let us clarify above statement.  A recommendation may be for 2% strength spray in terms of pure X for controlling household fleas; another recommendation may be for using a 0.1% strength spray of Y 50% EC for controlling mites.

(It is advisable to convert all units to metric units where calculations are simpler.)

1. For wettable powders

When using WP’s, a percentage strength spray is based on weight of pesticide to weight of water. Since 1 liter of water weighs 1 kg, we can use these formulas:

Active ingredient basis

Gms of WP/liter of water = (% strength desired x 1000 ) /  (% a.i. in WP)

Example: How many grams of X 40% WP to be added per liter of water to make up a 2% strength spray (active ingredient basis).

Solution:    Gms of 40%WP/liter = (2% x 1000)  /  (40%) = 50 g

Actual product basis

Grams of wettable powder needed per liter of water = (% strength spray desired x 1000)

Example: How much Y SP 95 is needed to make up a 0.15% strength spray (actual product basis).

Solution:   Grams of Y SP 95 = (0.15% x 1000)  =  (0.0015 x 1000) = 1.5 g per liter of water

       2.For liquids (EC’s)

Active ingredient basis

Cc(ml) of EC / liter water = (%strength spray desired x 1000) / (% a.i. in EC)

Example: How much X 57% EC should be added per liter of water to make up a 2% strength spray (active ingredient basis).

Solution:  Cc(ml) Malathion 57% EC per liter = (2% x 1000)  /  (57% )= 20 / 57 = 35 cc (ml)

Note for converting to metric units:

1 liter = 1000 cc (or Ml); 1 liter of water weights 1 kg (1000 g); 1 U.S. gallon = 3.78 liters; 1 lb. = 0.454 kg = 454 g; 1 kg = 2.2 lbs.

Further Reading:

http://www.nzdl.org/

About nkp

Hi ; I have had opportunity to travel widely and have keen watched whatever farming practices the local farmers were engaged in. Back home been growing gerberas mostly in polyhouses, but outside in kitchen garden as well. i love these hardy perennials. good for business too if done in a routine orderly scientific manner. Also engaged in farming of wheat and organic vegetables on a small scale for me and family. My service profile has been that of an electronic and telecom engineer and now am engaged in web site creation and blogging.