How to Calculate Fungicide Dosage to Spray in the Field

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How to calculate fungicides dosages per ha/acre

Fungicide: Fungicide is a chemical pesticide that has the ability to kill or arrest the growth of the fungi or fungal microorganisms. There are many fungicides that are available in the market. Various fungicides have different dosages and the dosage of each fungicide varies with the respective fungicide. They are toxic in nature. Hence, in order to decrease their direct toxicity when applied in plants, they are mixed with solvents or adjuvants.

            Accurate computing the amount or quantity of fungicide required to spray in a given area, and a uniform application rate is essential for effective control of fungal microorganisms. Commercial fungicides available in the market are commonly in the form of a wettable powder (WP), granules (G), or emulsifiable concentrates (EC).

Why calculate the fungicide dosage?   

Fungicide recommendations are often expressed in kilograms of active ingredient per hectare (kg a.i./ha) or percentage concentration of active ingredient (% a.i) of the fungicide in the final diluted solution. Therefore, the fungicide must be used in the correct dosage by diluting the exact amount of the concentrated form of the fungicide with a predetermined volume of water/other diluents/by spreading the exact amount of granules(formulation) required over a specific area. To achieve this, it is necessary to calculate the exact amount of fungicide material required for the area to cover.

            Each commercial fungicide possesses an active ingredient (a.i), the principal chemical compound that acts on the microbe. As the active ingredient (a.i) is highly toxic it is marketed/sold in a diluted form.

Recommended dosage of fungicides:

            Most fungicide recommendations are given in kg of a.i./ha or a.i (%).

FUNGICIDE DOSAGE CALCULATIONS

When recommendations is in kg a.i./ha

  1. For WP, WG, dust etc. (solid forms)

            Parameters required

  • area to spray
  • concentration of a.i. in formulation
  • recommended rate as kg a.i./ha

Formula: Kg of WG/WP/dust=(recommended rate x spray area (sq.m))/(a.i % of WG/WP/dust x100)

            kg of WG/WP/dust   =     recommended rate x spray area (sq.m) /                                                              
a .i % of WG/WP/dust x100

Example: Calculate the quantity of Captan 50% WG to apply in the one-hectare area if the rate of application is 0.75kg (750 gm) ai/ha.

           
            Quantity of Captan 50% WG/ha      =          (0.75 x 10000 (sq.m))/ (50 x100)

            Therefore, we require 1.5 kg/ 1500 gm of Captan 50% WG to apply in the 1 ha area.

  1. For Emulsifiable concentrates (EC)

Parameters required

  • area to spray
  • the concentration of commercial EC as a.i.% or kg/lt water
  • recommended rate as kg a.i./ha

When the concentration of EC given in a.i. (%)

Formula       

            kg of EC required = Recommended rate x area (sq.m) / a.i (%) in commercial EC x 100

OR

            kg of EC required = Recommended rate x area (ha)x 100 / a.i (%) in commercial EC 

Example: Calculate the amount of Isoprothiolan 40% EC to be sprayed in Paddy at the rate of 0.3 kg a.i./ha for 2 ha.

                                    Isoprothiolan 40% EC          =          0.3 x 2 x 100 / 40

            Isoprothiolan 40% EC for 2 ha       =          1.5 lt

Therefore, we require 1.5 lt Isoprothiolin40%Ec.

Example: Calculate the amount of Isoprothiolan 40% EC to be sprayed in Paddy at the rate of 0.3 kg a.i./ha for 5000m2.

            Isoprothiolan 40% EC          =          0.3 x 5000 / 40x 100

Isoprothiolan 40% EC for 2 ha       =          0.375 lt

Therefore, we require 0.375 lt isoprothiolin40%EC for paddy.

When recommendations is based on a.i.(%) in the spraying fluid/liquid

  1. For wettable powders (when dilution with water)

Parameters required

  • Spray volume in lt/ha
  • Desired concentration as a.i.(%) in the spray
  • Concentration in the commercial product (a.i.%)

            Formula:

                                    WP      =          ai % desired x spray vol. / ai % in commercial WP

            Example: Calculate the Captan 50% WP to mix in 1000 lt water to spray on Apple crop in 1 ha area?

                                    WP      =          0.125 x 1000 / 50

                        =          2.5 kg of Captan 50%WP in 1000 lt water

Therefore, we need 2.5kg Captan50% WP to mix in 1000lt water.

  1. For Emulsifying Concentrates (EC)

Parameters required

  • Spray volume in lt/ha
  • Desired concentration as a.i. (%) in the spray
  • Concentration in the commercial product (a.i.%)

Formula:

                                    WP      =          ai % desired x spray vol. / ai % in commercial EC

            Example: Calculate the Dinocap48%EC to mix in 10lt water to spray on 1Mango plant?

                                    WP      =          0.24 x 10/ 48

                        =          0.05 kg/5gm of Dinocap48%EC in 10 lt water

Conclusion: Therefore, this is all about fungicide dosage calculation and examples of fungicide dosage calculations. Furthermore, for any queries and other information regarding pesticide or fungicide dosage calculations, comment below.

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