One of the great fears when we have different crops in our care is the mixing of different insecticides with copper, a fungicide widely used in conventional and organic agriculture for its extraordinary properties in stopping the growth of fungi and, in some cases , bacteria.
When a foliar application is made, one tries to mix several components to reduce costs and gain convenience. Hence the question of whether can you mix copper with insecticideSo even add fertilizer to the mix.
Although the answer is complicated, given the large volume of insecticides on the market and the different regulatory countries, we will try to offer general concepts to understand when they can be mixed and when they are not.
read more: when to use copper in the olive grove.
Contents
Characteristics and compatibility of copper
Copper has been used for many years in agriculture because it has the ability to reduce multiplication and development of a large group of fungi, algae and bacteria.
Also elicitor effect, which results in the activation of plant defense mechanism, based on complex plant pathways to attack fungi or isolate the pathogen and delay its progression.
This element of the periodic table is a metal called copper oxide or copper(II) metal and we have different forms of presentation on the market:
There are very high concentrations, up to 70%, and other complexed coppers at less than 6%. However, what matters is not the concentration of copper in the container, but the amount that manages to get inside the factory.
Complexed copper has proven to be a fairly effective current tool for introducing a low but sufficient concentration of this element inside the plant.
Additionally, they tend to have good compatibility and generally can be mixed with insecticides.
When does copper cause problems?
Quick answer: when too much copper gets inside the plant.
In other words, when biostimulating nutrients are mixed, they increase the entry of copper inside the plant through both the foliar and root routes. However, the greatest dangers of phytotoxicity in this case are found in foliar applications.
In this group we include the following components:
- Urea
- Amino acids
- Organic components: monosaccharides (sugars), carboxylic acids, fulvic acids, etc.
- Algae and marine microalgae
- Glycine-betaine
All this and, surely, we leave some in the inkwell, either they complicate the copper, or they increase its introduction into the plant. For instance, urea increases leaf cuticle permeabilityit therefore facilitates the entry of all the elements that accompany this treatment.
It is the same for amino acids, algae and other components. If a high concentration of copper is mixed with these elements, it is likely that in sensitive crops there is a phytotoxicity problem.
At least, the conditions are met for it to be so. Therefore, coppers containing complexes or amino acids generally contain no more than 5-6% metallic copper.
Solved that, can you mix copper with insecticide?
Let’s go on.
Can copper be mixed with an insecticide?
In general, insecticides do not increase copper uptake or vice versa, so in most cases there will be no phytotoxicity concern in the mixture unless is clearly specified on the insecticide.
To give a clear example, in the stone and pome fruit trees it is protocolized to apply the paraffin oil + insecticide + 50% copper oxychloride mixture.
This treatment is indicated to control red spider mite, anarsia, tooth, San José lice and aphids, applied before flowering. Insecticides are commonly used pyrethroids, pyriproxyfen, fenoxycarb That is phosmetfor example.
Sources of copper with sulfur
However, care should be taken with forms of copper that contain sulfur, such as copper sulfatebecause if applied at high temperatures or soon after application of an oil-based insecticide, such as paraffin oil, incompatibilities may exist.
Maintain an appropriate pH of the mixture
Finally, mixing copper with insecticides should always be at an appropriate pH for foliar treatment. We are talking about a range of 5 to 7.5 in general terms.
In this case, the insecticide should always be stored in a stable pH range. It is not worth drastically lowering or increasing its pH and then compensating until it reaches the desired value. This can cause the components of the insecticide to denature and prevent it from working or, worse, cause phytotoxicity to the crop.
calcium polysulfide
Due to the particular characteristics of this acaricide, preventive fungicide and insecticide product, it is generally not recommended to mix it with copper, since it is quite strong, so it is generally recommended alone (without mixing with other insecticides or treatments).
In summary, copper can be mixed with insecticides with great care where the insecticide comes from and as long as no high organic content nutrients are added. The pH of the treatment must be carefully controlled and a small compatibility test (1 or 2 trees or plants maximum) in case of doubt.
In this type of case, it is always necessary to contact the technical or commercial specialist for the sale of insecticides or copper.