Proper Tank Mixing Using the Jar Test
Tank mixing pesticides saves time and money, but if done incorrectly, can lead to plant injury, damaged spray equipment, or a useless mix. Typically, pesticide labels will provide information on pesticide mixtures that lead to phytotoxicity (plant injury). This type of mixture is chemically incompatible. Some mixtures, however, may result in physical incompatibility, which is usually not mentioned on product labels. A physical incompatible mixture may lead to a foamy, flaky, gelatinous or sludge-like product that is ineffective on the target pests. A jar test can quickly determine physical compatibility.
Add one pint of water to a glass jar with a lid. (Use the same water source that will go in the tank.).
Check spray water pH and adjust if necessary. Often, the pesticide label will give the optimal pH range for best results.
Add pesticides one at a time, and shake vigorously after each addition. The pesticides should be added in the following order:
- water soluble pouches – 1 tbs
- wettable powders – 1 tbs
- dry flowables – 1 tbs
- capsule suspensions – 1 tsp
- emulsifiable concentrates – 1 tsp
- soluble liquids – 1 tsp
- soluble powders – 1 tsp
- surfactants and other adjuvants – 1 tsp
- fertilizers – use a scale to weigh out 1.1 grams
After all products have been added, shake again, let the solution stand for 15 minutes and then shake one last time and observe the results.
• Jar is cool to the touch, and mixture is smooth.
• Layers form quickly after stirring
• Mixture is clumpy, grainy, or foamy, or becomes sludgy
• Jar is warm or hot to the touch
If the mixture is incompatible, do not use the mix of chemicals on your plants. You could re-do the jar test (with a clean jar) to see if changing some steps will improve the mix:
• change the order of mixing
• change the water supply
• change the pesticide brand and/or select a different formulation
If the mix is compatible, add pesticides to the spray tank in
the same order as used in the jar test. Rinse all utensils and
jars and pour the rinse water (rinsate) into the spray tank.
Triple rinse and discard the jar.
If you own an iPhone or Android phone, there are several free apps available that help with tank mixing: TankMix by DuPont, Mix Tank by Precision Laboratories, Mobile Ag Tank Mix by Marrone, and Syngenta TankCalk.