Generally, pesticide application in field is calculated and applied based on area (For E.g. gm active/hectare). Concentration of the chemical not taken into account. But, concentration of a chemical playing major role for determining efficacy. The concentration may vary based on the dosing volume.
I would like to know the logic behind area (dose) wise application.
When applying pesticides, water acts as a means of delivering the product to the plant. Meaning that we may use 1 liter / ha in 400 liters of water or 800 liters. This varies depending on the amount of vegetation cover to be treated. After treatment the water evaporates and the pesticide or the preparation remains on the surface of the leaves with high concentration.
The concentration may vary depending on The volume of water but the applied dose remains the same. if a doctor gives you one Aspirine, you can take it with a glass or a bottle of water, final result is the same
I am partially agree with the answer of Ikbal Chaieb. Whenever anybody recommend the dose per hectare even with the volume in which the product will be diluted (for example 1 liter of pesticides in 100 liters of water), here if we maintain the concentration, we may not maintain dose per unit area because the growth of the crop vary from sowing to either fruiting or harvesting of the crop. Therefore, it is advisable to recommend the application of pesticide in its concentration with required quantity of spray fluid not only to obtain the best efficacy of the product but also avoid or delayed the development of resistance in pests against particular molecule. If we apply the molecule based on dose/ha at early growing period of crop, it may cause phytotoxic effect on crop plants.
The logic behind the area wise (Dose/ha) pesticide application may be for the benefit of manufacturer to fix the sales target.
4 basic ways of stating dosages:
1. Amount of active ingredient (pure chemical) needed per hectare or acre.
2. Amount of actual formulation (i.e. Carbaryl 50 WP or Carbofuran 3 G. etc.) needed per hectare or acre.
3. Amount of actual formulation needed per liter or gallon of water.
4. As a percentage concentration in the spray water.
Type 1 and 2 dosages are suited more to large plots or to those pesticides (especially herbicides) needing very accurate dosage application. Sprayer calibration is needed in both cases to determine how much water to use and how much pesticide to add to each tankful.
Type 3 and 4 are very general recommendations best suited to smaller plots or where dosage accuracy is not critical.
In detail:
1. Amount of active ingredient needed per hectare/acre: For example, a dosage might be given as 2 kg active ingredient (a.i.) Carbaryl per hectare. This means 2 Kg. of pure (100%) Carbaryl. Since actual pesticide formulations vary in strength from 1% up to 95%, it takes some math to figure out how much of a given formulation is needed to supply a given amount of active ingredient. If the local pesticides supply store sells Carbaryl 50% WP, the farmer would need 4 kg for each hectare in order to supply 2 kg active ingredient.
Note that nothing is said about how much water the farmer should mix with the pesticide when he sprays it on the plants. This will depend on plant size, plant density, and the degree of coverage desired. The only way to find out how much water is needed is to calibrate the sprayer.
2. Amount of actual formulation needed per hectare/acre: For example, a recommendation calling for 4 liters of Malathion 50% EC per hectare or another one for 2.5 lbs. of Carbaryl 50% WP per acre. This type of recommendation is somewhat simpler than type 1 since it's given in terms of actual formulation rather than active ingredient. However, the farmer still needs to know how much formulation he needs for his field's area and how much water it will take to provide adequate coverage with his sprayer. This requires sprayer calibration.
3. Amount of actual formulation needed per liter Or gallon of water: For example, Malathion 50% EC per liter of water or 2 tablespoons of Carbaryl 50% WP per gallon of water. This type of recommendation is much more convenient than types 1 and 2 since no sprayer calibration or dosage calculation is needed. The drawback is that the actual amount of pesticide the farmer actually applies on his field depends entirely on how fast he/she walks while spraying, how coarse or fine the spray is, and how much pressure is used. However, if proper guidelines are followed, type 3 recommendations are precise enough for most conditions and are the most feasible for small farmers. They should not be used for most herbicides where accuracy of dosage is critical.
4. As a percentage concentration in the spray water: This is basically the same as type 3, except that the concentration of pesticide in the spray water is given in terms of percent rather than cc/ liter or tablespoons/gallon. Such recommendations are usually based on percentage by weight, although sometimes a volume basis is used when dealing with EC's (the actual differences are slight). In addition, the percentage figure given may refer to active ingredient or to actual formulation.
In addition to the answers provided the dose rates (Concentrations) recommended by products manufacturers are validated at National Level during registration of the respective pesticides in various countries- For example manufacturer can recommend " 1.5Lt/Hacters of a formulation X and a spray volume of 200 liters per hacter" Authorities need to confirm if the recommended (including lower and higher rate) work.
Implications:
(i)If you apply he same formulation and spray 400 Liters in a Hkt it means that you have overdosed.
(ii)If you apply 50 Lts per hacter of the same formulation it means you have under dosed.
To ensure that you are not overdosing or under dosing you need to conduct calibration (spraying water in a known area to taking into account nozzle height, walking speed and other factors) and use the data to verify conditions leading into recommended spray volume.
Otherwise you will have to divide the spray volume with volume of spray tank and calculate number of tanks required to deliver 200 Lts.
The rate per area is useful because it is the way that a grower will relate to and use the product. Sadly, it is a poor measure for the scientific understanding of biological effects.
1) toxicant is not generally used in pure form. If liters per hectare remains constant, then the rate of formulation components increases as toxicant/hectare increases. This alters atomization properties of the applied product.
2) Total applied dose is a function of the number of droplets, the size of droplets, and the toxicant per droplet.
3) The size distribution of droplets in the spray cloud and the energy those droplets possess, influences the distribution of toxicant on the target surface. This is also influenced by formulation components and the nature of the target surface.
4) The distribution of toxicant influences the rate the target (or non-target) organism acquires the toxicant.
5) Toxicant will accumulate in the target so long as acquisition rate exceeds the rate the organism metabolizes the toxicant to non-toxic metabolites.
The logic behind the area-dose (dose/ha)
pesticide application is simple. The concept is to administerr the experimentally determined and recommended amount or quantity of an active or formulated chemical principle sufficient to destroy "the target pests or pathogens populations" within a given enclave with little or no side effects. The logic of the concept is not to overdose the area and as such exterminate several non-target species, and cause disruption of the food chain/environment in addition to overshooting the farm overhead and production costs; or to under dose it and hasten the development of resistance to the chemical principle in the treated pests/pathogens and thus encourage emergence of more stubborn and destructive mutants/species amongst the treated populations
Well had a great clarity of the insecticide application, but what should be the best term for application
Dose per hectare
Dosage per hectare
Which one is correct, what's difference between dose and dosage
Which one should we use as synonym to application rate of any insecticide please
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