Can I mix insecticide and fungicide?

When there are multiple issues to deal with, it might seem like you’re spending every weekend spraying your lawn with a different product.

If you have a large area to cover, combining liquid products into a tank mix and applying them at the same time can help save time and energy, and make keeping your lawn in tip top shape that much more enjoyable.

The trick with tank mixes is first understanding whether the active ingredients in the insecticides and fungicides you plan to use are compatible.

The labels of some products will carry a compatibility chart indicating which components are compatible, while others will warn against trying to use it in a tank mix. Some herbicides and fertilisers can also be added to a tank mix.

Here’s an example of compatibility information on the label of Indigo Recruit 200 SC insecticide.

Tank mixes containing incompatible chemicals can separate, form lumps, sludge or foam that won’t spray evenly or at all, or cause damage to your lawn.

If there’s no compatibility information on the label, it’s best to do a mix test in a jar before using a tank mix on your lawn for the first time.

Conducting a mix test

Make sure you’re wearing the appropriate protective equipment, such as safety glasses, gloves and boots, and do this test in a garage or shed away from food, pets and children.

Don’t try to combine more than two products in one batch, and be aware that wettable powders and ECs will generally not mix.

Pour 500ml of water into a screw top glass jar. Then add the chemicals, in proportion, to the jar in this order: wettable powders, flowables, water solubles (SC), emulsifiable concentrates (EC) and wetters.

  • A wettable powder is a dry powder formulation that forms a suspension when mixed with water before spraying.
  • Flowable is a liquid or viscous insecticide concentrate.
  • Water soluble is usually a powder that dissolves in water.
  • Emulsifiable concentrates contain an insecticide and emulsifying agent which are diluted with water.
  • A wetter, also known as a surfactant, helps chemicals to spread and penetrate the plant surface.

As an example, if you intend to spray 1L/ha of the herbicide glyphosate and 200ml/ha of the insecticide bifenthrin, use a disposable syringe to place 10ml of glyphosate and 2ml of bifenthrin into the jar.

Put a lid on the jar and shake until the contents are mixed well. Allow the jar to stand undisturbed for two hours, then look for any obvious signs of incompatibility.

Some settling of flowable or powder products is normal. But if it’s difficult to re-suspend sediment, it may cause blockages and uneven application rates or it may be a reaction that reduces the effectiveness of one or both chemicals. In this case, the chemicals should be applied separately.

Compatibility is not the same as safety

You can now use the test mix to check whether it is safe to apply to your lawn. Some chemicals will be compatible in a mix, but combined can make one or both products less effective or become toxic to grass.

The likelihood of damage increases if the application instructions are wildly different. Make sure both can be applied at similar times of day or at the same temperature range. If this is the case, spray a small section of your lawn and wait a few days to observe the results.

If the test patch is unharmed, you can be reassured and go ahead with spraying the entire lawn, if necessary.

Recommended products

myhomeTURF has a wide range of insecticides and fungicides available through our online store.

Source:  https://www.myhometurf.com.au/lawn-tips/can-i-mix-insecticide-and-fungicide/

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