What Does a Pesticide Applicator Do?

The pesticide's original medicine cannot generally be used directly. It must be processed into various types of preparations before it can be used. The type of preparation is called a dosage form, and commercial pesticides are sold to users in a certain dosage form. At present, the most commonly used dosage forms in China are more than ten dosage forms such as emulsifiable concentrates, suspensions, wettable powders, powders, granules, aqueous preparations, poison baits, mother liquors, and mother powders.

Agrochemical type

Most pesticide formulations are used after being formulated into a sprayable state before use, or after being formulated into poison bait, but powders, seed dressings, ultra-low-volume sprays, fumigants, etc. can be used without preparation.

The pesticides that farmers generally use on crops become formulation pesticides, that is, pesticides formed by the configuration of the original pesticide pesticides. Common pesticide formulations include powders, wettable powders, suspensions, dry suspensions, granules, etc., then How can we better judge the quality of pesticide formulations? Then we have to judge from the following seven aspects.

Agrochemical active ingredient content

The active ingredient content is the most important indicator in pesticide formulations and is expressed in mass percent grams / kg or grams / liter. Active ingredients refer to specific chemical structural components with biological activity in pesticide products. Biological activity refers to the interference, destruction, and killing effects on the behavior, growth, development, and physiological and biochemical mechanisms of insects, mites, germs, rats, weeds and other harmful organisms. It also includes the regulation of animal and plant growth.

Fineness of agricultural chemical powder

Powder fineness is one of the quality indicators of powder pesticide preparations (powder, wettable powder, suspension, dry suspension, granule). Expressed as a percentage that can pass through a certain sieve. For example, Japan and the United States stipulate that the fineness of the powder is 98% through a 45 micron sieve (325 mesh sieve). China currently only requires 95% of most powders to pass a 75 micron sieve (200 mesh sieve). The efficacy and fineness of powders are closely related. Within a certain range, the efficacy is inversely proportional to the particle size. The smaller the particle size of the contact insecticide, the larger the contact surface between the unit weight of the agent and the insect body, and the better the contact effect. In gastric toxic pesticides, the smaller the particle size, the easier it is to be swallowed by pests and diseases, and it is easier to be absorbed by the intestine after eating to exert toxic effects. However, the granules are too fine, the volatilization of active ingredients is accelerated, the efficacy period is shortened, and the drift during spraying is serious, but it will reduce the efficacy and be harmful to the environment. Therefore, when determining the fineness of the powder, the appropriate particle size should be determined according to the characteristics of the original drug, the conditions of the processing equipment and the level of the application machine.

Agrochemical bulk density

Bulk density is one of the quality indicators of powders. Bulk density is the mass of powder per unit volume (g / ml), also known as performance specific gravity. According to the degree of filling compactness, the bulk density is divided into two types: loose bulk density and compact bulk density. The former is the bulk density when the powder naturally fills the container. The latter is the bulk density when the powder is packed relatively tightly after the powder is loaded into the container through prescribed mechanical vibration. The small bulk density of the same powder indicates that the powder particles are fine and the powder has a low water content. Under the condition that the measurement methods are consistent, the bulk density of the powder and the wettable powder is related to the bulk density of the filler used, the type of the auxiliary agent, the type and concentration of the active ingredient, and the fineness of the powder, and the bulk density of the filler has the greatest influence.

Pesticide-type wettability

One of the quality indicators of wettable powder pesticide formulations is the time it takes for the wettable powder to be sprayed from a certain height to the surface to be completely wet. The measurement method developed in China is to pass a 5 g sample passing through a 40-mesh sieve (approximately 400 microns), and at a distance of 100 mm from the water surface, sprinkle 30 ° C standard hard water (342 mg / liter, calcium: magnesium = 80: 20) In a beaker, record the time it takes for the sample to be completely wetted. Many insoluble original medicines cannot be wetted by water. To change this property, a certain amount of good wetting agent must be added during processing. Wetting agents can reduce the interfacial tension between pesticide particles and water, so that the powder can be quickly wetted and dispersed by water. Wettable powders not only require the formulation itself to be wetted with water, but also require water to be diluted at the dilution factor specified in use to make the suspension spray on the plants, which can wet the plants well and expand. . After the wettable powder suspension with poor wettability is sprayed on the plants, it cannot be wetted and spread well, and the liquid medicine is easily rolled down from the leaves, which reduces the effectiveness of the medicine. Therefore, it is common to add some surfactants when applying wettable powders, which will improve the efficacy, which may also increase the wettability of the suspension. FAO stipulates that the wettability of wettable powder is no more than 1 or 2 minutes, and our country generally stipulates no more than 5 minutes. The purpose of limiting the wetting time is to make it wet with water quickly and to disperse into a uniform suspension when diluted with water before application.

Agrochemical suspension rate

Wettable powders, suspensions, water-dispersible granules, microcapsules and other pesticide formulation quality indicators. It is diluted with water to form a suspension, and after standing at a specific temperature for a certain period of time, the percentage of the amount of the active ingredient still in the suspended state in the amount of the active ingredient in the original sample. After the above pesticide formulation is diluted with water and becomes a suspension, it is sprayed with a sprayer. It is required that the particles of the active ingredient of the pesticide can be suspended in the suspension for a long time without sinking to the bottom of the sprayer. The liquid is more uniform and has a good control effect; if it sinks to the bottom, the concentration of the liquid sprayed early will decrease, and the amount of medicine on the plant will be small, and the control effect will decrease; and the concentration of the liquid sprayed late may be too high It causes phytotoxicity to plants, so the level of suspension suspension is an important factor for the effectiveness of the preparation. In China, the suspension rate of the dilution of pesticide preparations is required to be between 50% and 70%, and a few products require 80%.

Agrochemical emulsion stability

One of the quality indicators of emulsifiable concentrate pesticide preparations. It is used to measure the uniformity and stability of the dispersion state of pesticide liquid beads in water in the emulsion formed by emulsification oil diluted with water. Emulsifiable pesticide preparations need to be diluted with water to form an emulsion and sprayed. Most of the emulsions used in agriculture are oil-in-water (O / W) type. It is required that the liquid beads can be evenly distributed in the water for a long time, and the oil and water are not separated, so that the effective component concentration in the emulsion is kept uniform and the drug effect is fully exerted To avoid phytotoxicity. The stability is related to the type and amount of emulsifier used in the preparation of emulsifiable concentrate. FAO's test method for emulsion stability is: the samples after thermal storage stability treatment are diluted 20 times with standard hard water, observed immediately after shaking, should be completely emulsified, and the volume of cream separated after half an hour is generally not greater than 2ml, the volume of cream and oil slick separated after 2 hours of parking is generally not more than 4ml. After being left for 24 hours, shake again, and the isolate should be able to re-emulsify. The emulsion stability measurement standard formulated in China is: the emulsifiable concentrate is diluted by a certain multiple (200, 500, 1000 times) with standard hard water at 342 mg / l, mixed into a 100 ml graduated cylinder, and allowed to stand at 25-30 ° C for 1 hour Observe that there should be no oil slick, slick oil or precipitation. If the dilution factor is too high, such as 1000 times, even if the emulsion is not stable enough, a small amount of oil slick or cream is separated, it is not easy to observe, this observation method is not reasonable. The dilution factor with standard hard water should be uniformly set to 200 times.

Agrochemical smoke formation rate

One of the quality indicators of pesticide smoke. It is expressed as a percentage of the content of the active ingredient of the pesticide in the smoke during the combustion of the smoker and the content of the active ingredient of the pesticide in the smoker before the combustion. In the process of burning smoke, its active ingredients are affected by heat, and only the volatilized or sublimated smoke will have a control effect, and the rest will be decomposed by heat or left in the residue. The smoke formation rate of the active ingredient of the smoker must be greater than 80%, and the smoke formation rate of the active ingredient of the mosquito coil must be greater than 60%. Different pesticides at the same temperature, or the same pesticide at different temperatures, the smoke generation rate is different, and the temperature depends on the pesticide formulation. A pesticide formulation with a high smoke generation rate should be selected to be processed into a smoking agent.