How to Mix Pesticides Rationally
Mixing pesticides with pesticides is a rather complex issue, and not all pesticides can be mixed. When mixing, the following points should be noted:
(1) pH is an important factor affecting the effectiveness of each component. Under alkaline conditions, carbamates, pyrethroid insecticides, thiram, zineb and other dithiocarbamate fungicides are prone to hydrolysis or complex chemical changes, thereby destroying their original structure. Under acidic conditions, 2,4-D sodium salt, MCPA sodium salt, amitraz, etc. will decompose, thus reducing efficacy.
(2) Organic sulfur and organophosphorus pesticides cannot be mixed with pesticides containing copper preparations. For example, mixing dithiocarbamate fungicides and 2,4-D salt herbicides with copper preparations will cause the relevant components to complex with copper ions and lose activity.
(3) Microbial-derived insecticides and systemic organophosphorus insecticides cannot be mixed with fungicides.
(4) When mixing emulsifiable concentrates or wettable powders, no layering, floating oil, precipitation or similar phenomena should occur.
(5) Phytotoxicity of the mixture should be avoided; chemical changes in the active ingredients of the mixture may cause phytotoxicity. For example: mixing lime sulfur mixture with Bordeaux mixture can produce harmful copper sulfide and also increase the content of soluble copper ions; propanil, butachlor, etc. cannot be mixed with organophosphorus or carbamate insecticides.
(6) Main types of mixing: 1. Mixing two or more insecticides; currently the main ones used include jiadi powder, yidi powder, xindi emulsifiable concentrate, kangyaling, fuguo, etc. 2. Mixing one or more insecticides with one or more fungicides; the main forms include fenitrothion plus isoprothiolane, dimethoate plus carbendazim, methamidophos plus isoprothiolane, etc., most of which are prepared immediately before use. 3. Mixing two or more fungicides; the main varieties include banshuang, metalaxyl mancozeb, duoliu suspension concentrate, and tuijunte. 4. Mixing two or more herbicides; in China the main applications include bentazone plus 2,4-D butyl ester used on wheat; atrazine plus acetochlor, and atrazine plus 2,4-D butyl ester used in corn fields, etc. 5. Mixing insecticides, fungicides and herbicides.
Excerpted from: Hua Feiwen. How to Mix Chemical Fertilizers and Pesticides[J]. Rural Hundred Know-All, 2017, (08): 48-49.