Copper fungicides

Bill Brett | 06 January, 2022


          
            Rust on Chrysanthemum NZ

Why use Copper fungicide?

Copper compounds have been used for a century as a preventative fungicide. Copper fungicides can be used on fruit, vegetables, and ornamentals, for prevention of many fungal and bacterial diseases on fruit and vegetables, including black spot, leaf curl, shot hole of fruit, blights, leaf spots and downy mildew of vegetables.

When to apply Copper fungicides

Copper fungicides are applied to foliage of susceptible plants just prior to expected attack, or immediately after first sign. Because it works by forming a protective barrier on the leaf surface, thorough coverage is important and copper will need to be reapplied after heavy rainfall.

Is Copper safe for Bees?

Copper fungicides are safe to bees and beneficial insects, but it is always good practice to spray early in the day before bees begin foraging so the spray can dry before the bees come in contact.

Product comparisons

There are four different copper fungicides available to home gardeners in NZ. 

Yates Copper Oxychloride

An old form of copper which leaves a high copper footprint and is now losing favour with gardeners. Copper oxychloride is also one of the ingredients in  Yates Fungus Spray.Withholding period 1 day.

Grosafe Free Flo Copper

Copper hydroxide, a natural copper which has been formulated into a fine water dispersible granule. It has a bulk density the same as water, it flows and measures like water, making it easy to measure and mix. It has a particle size 20 times finer than copper oxychloride. This provides better coverage and adhesion and consequently better results from lower rates of use. This is the only copper fungicide which is BioGro certified organic. It is often mixed with  Grosafe Enspray 99 oil for use on fruit trees. Withholding period-Nil 

Yates Liquid Copper

This contains Copper ammonium acetate in a liquid formulation. This is easy to measure and provides good coverage. The major drawback with this product is that it is very sensitive to the acidity of water it is mixed with and should not be mixed with any other pesticides. Whilst it is used successfully in commercial orchards, there have been many gardeners report plant damage.
Withholding period 1 day.

Kiwicare Copper Liquid

 This contains tri-basic copper sulphate in a liquid formulation. This product has the same advantages and disadvantages as  Yates Liquid Copper.It should not be used in mixture with other pesticides. Withholding period- Nil 

Our recommendation

If you are using a different copper switch to Grosafe Free Flo Copper today —you should get better results from lower use rates and lower cost. 

Grosafe Free Flo Copper is the only copper with Biogro Organic Certification.

Grosafe Free Flo Copper is available from most large independent garden centres and from some Mitre 10 Mega stores.