Copper pesticide approved for Canadian cannabis

Different minerals found in soil provide plants with essential nutrients, aiding in their development and growth. One element, though, has strong antimicrobial properties. Health Canada approved a copper-based fungicide for use on cannabis crops. Label instructions associated with the pesticide do consider inhalation risks and, inadvertently, avoid a potential reactivity concern.

Copper [II] Sulphate Pentahydrate

Copper salts easily dissolve in water. Pentahydrate is no exception and will dissociate as it dissolves. Health Canada approved Harvest Miracle as a treatment for powdery mildew. This vibrant blue salt will solvate into Cu [II] ions and sulphate when mixed with water, allowing cultivators to spray the formula onto plants.

Sulphate acts as a carrier to bring copper ions to the surface of fungal cells. The aqueous solution will dry out after it is sprayed onto plants. Copper(II) ions remain stable in solution but are chemically reactive and can form complexes or new compounds with substances in the environment. Ionic copper will attack mildew by disrupting cell membranes, DNA, and even metabolism.

Health

Copper is an essential mineral for plants and humans, in small, trace amounts. Health Canada sets its limits for heavy metals based on standards set by the European Pharmacopoeia. Copper is classified under ICH Q3D as a Class 3 element. This means that, while it is regulated and can be toxic at higher levels it has relatively low toxicity by oral exposure compared to highly toxic metals. The guidelines permit a daily oral exposure limit of 3 milligrams with an inhalation limit set at one-hundredth of that dose.

Metal sulphates are far more stable against thermal degradation compared to elemental sulphur. This means that sulphate pentahydrate will only release sulphur oxides under intense heat that likely exceeds the temperature of a normal cannabis ember. Smoke produced by cannabis treated with the spray could, however, release copper oxides relatively more easily.

Accounting for the potential risk to human health, the pesticide is limited to vegetative plants. Harvest Miracle is restricted from use on flowering cannabis plants, per label instructions. For inhalable extracts, we suggest that cultivators avoid extracting whole-plant material that was treated with sulfate or sulphur products at any stage of cultivation.

Reactivity

Metallic copper, the common material, is the nonionic form of the element. Copper ion can exist in two different states, (I) or (II). Health Canada approved a salt that releases the stable Cu² form. Cuporous Copper, on the other hand, does not survive in solution. Interestingly, though, this January, Analytical Chemistry released a study exploring complexes of copper [I] and THCa.

Positive charges in the ionic metal can weakly fuse to negatively charged cannabinoids. The experiment was conducted to test whether a proposed analytical method can accurately quantify THC and CBD. The reaction was proven with Cu¹ salt, which follows distinct characteristics. The ion, therefore, cannot be compared to the properties of Cu[II] or used to predict reaction outcomes with pentahydrate and cannabis. Regardless, applications in the vegetative stage would negate interactions between copper ions and cannabinoids.