Who Should Use This Technique
This method is simple and costs very little. However, some equipment, including an electric balance and pipettes, is needed. For this reason, the method will usually be used by extension staff. If you do not have a Table showing the compatibility of pesticides, you can check compatibility using this method.
Applying Several Pesticides Together
If you want to apply several kinds of pesticides at once, all mixed together, you must be careful that all the pesticides are compatible with each other. If they are not, there may be residue problems and chemical injury to crops, or the pesticides may not be effective. This is because inappropriate mixtures cause incompatible phenomena such as non-homogeneity, layer separation, precipitation, change in viscosity, aggregation, flocculation and gelatinization of the mixture. These in turn cause nozzle clogging and uneven spray. To avoid these problems, the following method is recommended.
Choose the Same Kind of Formulations.
If you are mixing different pesticides together, it is important to choose the same kind of formulation. The formulation is indicated on the label of the chemicals you will use. This may be emulsifiable concentrate (EC), solution (SL), suspension concentrate (SC), wettable powder (WP), soluble powder (SP), dispersible granule (WG) or emulsion in water (EW).
Mixing Chemicals with Different Formulations
You can check the compatibility of chemicals in the following manner.
1) The following instruments are needed.
a) Two clear glass jars with lids (capacity about 250 ml). Mark one of the jars "with", and mark the other "without".
b) Several pipettes of 0.1 mL (for liquid chemicals) and a mg-balance (for solid chemicals).
c) A bulb sucker to suck chemicals. Don't suck a pipette with your mouth.
2) First, fill each jar with about 100 mL of water. Then, add each undiluted chemical into the pair of jars in the following order. WP, WG, SC, SP, SL, compatibility adjuvant (only for the jar marked "with"), and finally EC. The volume or the weight of the chemicals to be added depends on the recommended dilution factor of each chemical. Please refer to an example explained in Table 1.
3) The mixture in the jars should be stirred gently after each addition.
4) Cap the jars tightly with the lids, and mix the contents throughly by turning the jars10 times.
5) Leave the jars for 5 minutes. Then observe them, to see if there are any of the incompatible phenomena mentioned above.
6) If you find any incompatible phenomena in both jars, the combination should not be used.
7) If you find incompatible phenomena only in the jar marked "without", the combination can be used with compatibility adjuvant.
8) Even if you may find some of the incompatible phenomena with half an hour after mixing, if the phenomena disappears after the mixture has been turned upside down 3 times, this combination can be used, provided it is shaken or stirred frequently during application in the field.
1. Don't suck a pipette with your mouth.
2. Use only registered pesticides.
3. Pesticides should be chosen from those recommended for the crop.
4. A preliminary small-scale field test is recommended, to be sure there will not be any chemical injury to the crop.
Index of Images
Figure 1 Examples of Phase Separation (Left) and Flocculation (Right)
Figure 2 Possible Forming during the Test. If the Form of the Mixture Makes If Difficult to Observe, You Can Add a Few Drops of Deformer.
Table 1 An Example of Calculation of the Volume to Be Added
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