Herbicide

Classification of herbicides 

(A) the nature of the role of 

1 Herbicide 

Some herbicides, indiscriminately kill all weeds and crops, such as Herbicide herbicide, for example, sodium pentachlorophenol, Gramoxone and glyphosate and so on. 

2, selective herbicide 

Some herbicides can kill some weeds, but weeds are not valid for others, for some crop safety, but for some crops are harmful, what we called selective, with such features as selective weed herbicide agent. For example, chlorine can kill 2 A 4 Monochoria grass, water spinach, shaped sedge, water sedge and other weeds, while the barnyard grass, Paspalum distichum and other grass weeds invalid safe to rice paddy fields for , wheat, corn fields of use, but for cotton, soybeans, vegetables and other broadleaf crops is a serious injury. Another example is the enemy to kill barnyard barnyard grass, rice safety; West Jin to kill crabgrass, pigweed, and other annual weeds while the corn security; there diclofop, wild swallow can kill wild oats and dry Wheat security. 

Selective herbicide is not absolute, but relative, that is not selected herbicides on crops is also not affected, can kill weeds, but in a certain object, dose, time, method and conditions of the selection , choice is good or bad is determined by the selectivity coefficient, the so-called coefficient of a herbicide to kill (or inhibit) 10% dosage of crops and kill (or inhibit) 90% of the dose ratio of weeds, the coefficient bigger and more security, a selective herbicide selectivity factor greater than 2 before promotion. 

Herbicide selectivity coefficient = 

Kill or (suppression) the dose within 10% crop 

Kill or (suppress) the dose of more than 90% weed 

(B) the mode of action classification 

1, the absorption of the herbicide 

Some herbicides can be weed roots, leaves or both, respectively, absorption, transport through the conducting tissue of the body parts of the plant, destroying its internal structure and physiological balance, resulting in death of plant residues, which is called the suction with this feature is called the absorption of the herbicide herbicides, such as 2 A 4 Cl, glyphosate may be the plant stems, leaves absorb, and then moving to all parts of plants, including underground rhizomes, so glyphosate Control in addition to annual weeds, but also effectively Control in perennial weeds. 

2, the contact toxicity of the herbicide 

Some of the herbicides sprayed plants, only direct contact to the pharmacy to kill that part of plant tissue, but not the uptake and, with this feature tag name of the herbicide herbicides. These herbicides to kill weeds on the ground can only be part of the underground parts of weeds or perennial weeds underground reproductive organs are less effective, such as nitrofen, pentachlorophenol sodium. 

(C) to classify objects by spraying 

1, soil treatment agent 

That is, to spray herbicides on the soil surface or through the operation of the herbicide mixture of soil mix in the soil a certain depth, to establish a closed layer of herbicide to kill the germination of weeds. In addition to use of herbicides and soil treatment to kill weeds selectively physiological addition, in many cases is the use of selective herbicides to jet lag or the potential difference. Such as fluorine-bed Ling, nitrofen, West Jin, A fear of such. 

2, the stem treatment agent 

Herbicide that is diluted in a certain amount of water or other inert filler, spray processing of weed seedlings, the use of weed stems and leaves to eliminate weeds absorption and conduction. Address key is the use of leaf physiology and biochemistry of herbicides to achieve selective herbicides Seedlings purposes. 

(D) classification by application time 

1, treatment agent before sowing 

Refers to the soil before planting crops, closed treatment, such as the use of trifluralin cotton fields, wheat fields using the fear of wild wheat, cotton or wheat are herbicide spraying before sowing into the soil and mix the soil a certain depth in order to Root for the weed, bud absorbed, and can prevent or reduce herbicide volatilization and photolysis losses. 

2, pretreatment agent after sowing 

After the emergence in the crop before sowing soil treatment, this method is mainly used for weed coleoptile conduction growing point and young leaves absorb the herbicide, crop sprouts security. 

3, postemergence treatment agent 

Refer to weeds after emergence, the herbicide sprayed directly on the weed plants. Also some Herbicide, such as paraquat, glyphosate can be carried out in the weeds off students in the late treatment, postemergence herbicide absorption and can usually shoot other parts of the plant transfer of herbicides. 

(E) classification by application method 

Herbicides can be used in many application methods, such as by spray treatment, including the constant spray here, low-volume spray, micro spray, may also spread toxic herbicides and indigenous to a certain amount of soil mixed up Caesar Xirun facilities. EC or agent of some herbicides, such as molinate, Dan herbicide, grass evil spirits, bottle rejection can be used, or the use of the drip infusion device in rice processing. Herbicides to determine their physical and chemical characteristics of different application methods, such as trifluralin and other volatile herbicides to be used for soil treatment, and asked harrow mixed soil, if only poorly by foliage spray, and easy occurrence of injury to crops. 

(Vi) Classification of areas by spraying 

1, a comprehensive pesticide 

That a uniform comprehensive whole field spraying, including weeds and crops. This applies to high-selective herbicide and weed widespread in the whole field and the density of the crop to weed situation. 

2, band spraying 

Put the liquid within a limited range of continuous, fan-shaped nozzle can be used, such as planting crops of about 5cm or so deal with the spraying to eliminate weeds between crop to bring the plant, other than for the seed with the use of weed intercropping crops or artificial cultivators. Strip spray can save half to two-thirds or more of the drug, but need more spray machine accessories, other operations can be reduced about 15%. 

3, dotted spraying 

To deal with a limited area, such as grass or as a full crop spraying or after spraying the local supplement to the core distribution of weeds (perennial weeds such as Cyperus rotundus) for point of spray treatment. This method is targeted, more economical treatment. 

4, directional spray 

Control the direction of liquid spray, spraying the weeds or on the ground, as much as possible contact with crops. This is the nature Postemergence off with some of its contact toxicity of herbicides to crop or between the lines dealing with the protective spray. 

(Vii) Classification by formulation 

Herbicide formulations and processing quality of processing the efficacy of the herbicide much, should be based on a variety of herbicide mode of action of physical and chemical properties and processed into suitable dosage forms, can play its full efficacy. Currently there are liquid, water-soluble, wettable powder, suspension, emulsion, oil, granules, powders and so on. 

1, agent 

A certain concentration of water-soluble water-soluble herbicides dubbed, such as 20% of the chlorine agent 4 2 A 10% glyphosate. 

2, water-soluble powder 

Is a solid dissolved in water directly herbicides, diluted with water spray, economic, easy to use when you use soft water (water), as for hard water by adding sodium carbonate should be pre-or sodium bicarbonate in water to soften. For example, 2,4 - sodium salt, sodium pentachlorophenol, 2 A 4, chlorine, sodium, etc. can also be mixed with soil applicator. 

3 WP 

The original drug is often difficult to dissolve in water or organic solvents, so it with inert fillers and wetting agents in proportion to uniform mixing, grinding to a fineness of 300 mesh or more, can be diluted with water into a suspension, can be used for leaf spraying or soil surface spraying. It may also be mixed with soil applicator, which is the main processing of the current formulations, such as herbicides, chlorotoluron, simazine, diuron and so on. 

4, SC 

Also known as gum suspension agent, the original drug is not soluble or very little soluble in water and organic solvents, is to a high fineness of the original drug and a number of wetting agents, dispersants, thickeners such as concentrated liquid suspension even dubbed , Duishui into the stable after the suspension. Should make stems, leaves sprayed, because of this high dosage of crushed fine, suspension property, a great, strong adhesion, so the time for sprayed effective than the WP. 

5, EC 

Is a homogeneous oily liquid dosage forms, the original drug from the herbicides, organic solvents and emulsifiers fusion made into emulsion diluted with water spray. The formulation used stem, leaf processing, such as propanil, butachlor and so on. 

6, granules 

Granular herbicide formulations. It is applied to the soil in the water, the pharmaceutical from the particles released slowly diluted, absorbed by weeds play a role, used for soil treatment, especially in paddy fields than any other formulation applicator easy and safe. 

7, oil 

By the original drug with appropriate herbicide organic solvent (oil) is made, do not exchange water use, suitable for ultra-low volume spray. 

8, powder 

Herbicide with the original powder and the inert powder mixture after grinding. Available duster spraying, or make toxic soil applicator. 

(H) Classification according to chemical structure 

Different types of herbicides and similar compounds, the chemical structure of different genes on the biological activity of herbicides replaced with the impact of regularity, and thus classified by the chemical structure of both herbicides scientific, systematic, detailed, and easy to remember. 

Existing herbicides can be divided into phenols, phenoxy acid, benzoic acid, diphenyl ethers, together pyridine, carbamates, thio-carbamates, amides, substituted urea, are triazine, two nitrophenols, organic phosphorus, and miscellaneous epoxy phenoxy propionic acid phenyl ester, sulfonylurea, imidazolinone, and other heterocyclic compounds and so on.