How to mix pesticide and choose compound drug
As various plant diseases and insect pests appear very often and most of the drug can only prevent one kind of plant disease and insect pest, many farmers hope to receive comprehensive treatment by mixing two kinds or several kinds of drugs at one time; the other people also hope to improve the controlling effect and fast-acting property of drug by mixing the drug. Below three principles should be paid attention to no matter whether the drug is mixed or not, pesticide manufacturer reminds you.
The physical behavior should not be changed, which means that no oil slick, flocculation, sediment or discoloring should be appeared after mixing, meanwhile, no heat should be released or no bubbles should be generated. If the pesticides are all in the form of powder, or granules, fumigant and aerosol, they can be mixed; different dosage forms, such as wettable powder, emulsifiable concentrate, concentrated emulsion, suspension concentrate, aqueous solution and other liquors that use water as medium, cannot be mixed arbitrarily.
It should not cause chemical changes. Many drugs cannot be mixed with alkaline or acidic pesticide, this is because under Bordeaux mixture, lime sulphur and other alkaline conditions, carbamic acid ester, pyrethroid insecticide, thiram, milneb and other dithiocarbamate fungicides are easy to hydrolyze or have complex chemical change, thus it will destroy the original structure. Under acidic conditions, 2,4-D sodium salt, 4-chloro-O-tolyloxyacetic acid, sodium salt and amitraz will also hydrolyze and reduce the pesticide effect. Except for the alkaline and acidic conditions, many pesticide varieties cannot be mixed with the drug that contains metal ions. Dithiocarbamate fungicide and 2,4-D herbicide will generate copper salt that will reduce the pesticide effect after being mixed with copper compounds; thiophanate-methyl and thiophanate can have complexation with copper ion and lose activity. Except for copper compounds, other preparations that contain heacy metal ions, such as iron, zinc, manganese, nickel and other preparations, should be mixed carefully. In addition, lime sulphur will generate harmful copper sulphide when being mixed with Bordeaux mixture, which will also increase the content of soluble copper ions; propanil and butachlor cannot be mixed with organophosphorus and carbamate pesticide as some chemical changes may cause phytotoxicity.
Biopesticide cannot be mixed with fungicide. In order to make full use of its effect, below complementary effects should be considered as far as possible.
Compound insecticide, fungicide and herbicide can concurrently cure various plant disease and insect pests that occurred at the same time. By mixing the fungicides that have different bacteriocidal spectrums and expanding the control object, it can reduce the drug delivery frequency, but this requires appropriate opportunity and drug. For example, in the heading and filling stage of wheat, by mixing triadimefon, imidacloprid and monopotassium phosphate, it can not only control the aphid, powdery mildew and rust disease at the same time, but also can promote the growth of wheat flag leaf, increase photosynthesis, extend the wheat growing period and prevent the damage of dry hot wind.
Mix fast-acting drug with those drugs that have high pesticide effect and work slowly, for example, mix esbiothrin or chlorpyrifos with abamectin insecticide; by mixing the drug that have different mechanisms (no cross resistance), which can not only delay the rising of drug resistance, but also can improve the control effect and extend the expiry date of drug.
No matter mixing what kind of drug, the following principles should be followed: mixing and using the drug at the same time, besides, the drug should not be placed too long; dilute the drug respectively before mixing them. In addition, it should be tested in a small range firstly.
The higher aim of mixing drugs is reaching synergistic interaction, which needs strict scientific experiment and analysis. Many of its achievement have been transformed into compound preparations and can be bought from the shops. Any of the mixture should be limited to use when various plant disease and insect pests indeed occur or there is come object or situation that cannot be controlled by single drug. Besides, do not expand the application range arbitrarily and do not treat the mixture as “panacea”. It is most important to choose the appropriate drug according to different disease.