Chemical care: Mixing chemicals to combat turf problems

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Updated Aug 13, 2019
Photo: WaynesPhoto: Waynes

Mixing two or more chemicals to combat turf pests and disease and to promote turf health is a common practice. But it’s not as easy as just dumping chemicals together and hoping for the best. There are several key considerations before mixing chemicals:

  • Carefully follow the safety precautions on the most stringent product label you are mixing.
  • Be sure that the timing of the materials’ residual performance is adequate and will provide adequate control for your turf problems.
  • Determine the compatibility of the chemicals you want to mix. According to Tom Kroll with NuFarm, today’s formulations are mostly compatible with other chemicals. But, when in doubt, conduct a jar test.
  • Be sure you calibrate your chemical application system so that you apply the proper amount per square foot or per acre.

Mixing it up: Jar tests save you time and money

Liquid formulations offer more versatility when combining products. While not everything is compatible, you are not limited pre-packaged mixes. Again, to determine compatibility, always refer to the label. It will specify if you can mix the product with other chemicals. Also keep in mind that even when you are mixing chemicals, you must adhere to the labeled pesticide rate.

If the labels on your products give you the go-ahead for mixing, they may not always provide instructions for doing so. If not, the first thing you should do to determine compatibility is perform a jar test. Doing so will reveal most incompatibilities. Remember as you begin to mix chemicals for this test that they must be mixed in a specific order. Not following the order can result in incompatibility among chemicals and an increased risk to the person mixing the chemicals.

Start with a clear 1-quart glass or plastic jar. Add 1 pint of water (from the same water source you’ll be using for the tank mix). Next, add in chemicals in the proper order by using the WALE method:

  • First add Wettable powders and Water-dispersible granules,
  • then Agitate the mix,
  • add Liquids, surfactants and flowables,
  • then add Emulsifiable concentrates.

Allow the solution to mix thoroughly after you add each product. After you have added all the products, shake the jar to mix, and let it stand 30 minutes to one hour. Look for separation or settling. Incompatibility might also result in the formation of some solid material in the mix or surface scum – things that would hinder your ability to spray the product onto turf.

Going granular

As a lawn care provider, you can choose from a variety of combination products that come already mixed. These products combine fertilizer with other chemistries including herbicides, insecticides and fungicides. Most of these products that come pre-mixed are going to be granular formulations because manufacturers usually don’t offer pre-mixed liquid combination products.

Particularly with granular formulations, problems can occur with the SGN: Size Guide Number – the smaller the number, the better coverage you get. For example, you mixed some granular fertilizer with granular herbicide. It would be easy enough to just empty both bags into the hopper, but because they may be different size and weight, they would spread differently and, most likely, unevenly. In the end, your client would probably end up with striped turf.

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