Expert: Deborah J. Meier, Ph.D., Technical Development, Kocide LLC

Question: When looking at copper product labels, each product lists MCE. What does MCE mean and how do I figure out the amount of active copper in a product labeled rate for my tree nut crops?

Answer: MCE stands for metallic copper equivalent. It represents the amount of active Cu²⁺ ions that are in a product. The Cu²⁺ ions are the biological active form of copper. EPA regulates copper products by setting limits on the amount of active copper ions allowed per application and per year. Using walnuts as an example, EPA set the maximum single application rate at 4.0 lbs. MCE and the maximum annual rate at 32.0 lbs. active copper ions (MCE). Therefore, if you were to see a recommended rate of 4.0 lbs. (MCE or formulated product) how do you know what that means for the amount of copper you are using?  Also see “US EPA Proposes Reduced Copper Rates. What Does That Mean to Me?”

Each copper label will list the percent active ingredient as well as the percent MCE for that product. If the product is a liquid formulation, the amount of metallic copper per gallon is also listed. Determining the amount of active ingredient in traditional synthetic pesticides is determined by the percent active ingredient, something you can’t do with copper products. You need to work with the MCE or the MCE per gallon or pound depending upon the formulation.

The calculation to determine MCE varies depending on product formulation. Figuring out the amount of active copper in dry copper products is easy and has a simple formula. Figuring out the amount of active copper with liquid formulations requires some extra math steps. Below is the calculation method using walnuts as an example:

Copper labels list the maximum annual rate per acre and the rate for their formulation. In walnuts, Kocide® 3000 lists a maximum annual rate as 107 pounds; so 107 x 0.30 = 32 lbs. MCE. Cueva^® lists a maximum of 203 gallons per year; so 203 gallons x 0.16 (MCE/gallon) = 32.48 pounds rounded = 32 pounds MCE. These rates reflect the EPA maximum annual rate of 32 pounds Cu²⁺ ions (MCE)/A.  

One thing you can discern from figuring out MCE rates is that the formulation does influence the rate. While the amount of MCE is important, following rates on labels is more important because not all products are created equal. If one adjusts rates to a certain MCE and that is above or below the label rates, efficacy can be affected. Always follow label use rates based on the product label versus using a preset MCE rate.

Kocide^® 3000 with its advanced formulation technology delivers high level of efficacy using lower product use rates compared to most commercial products and reduces the amount of copper put into the environment versus higher MCE dry formulations.

_{Cueva® is a trademark of W. Neudorff GmbH KG}

_{Nu-Cop® 3L is trademark of Albaugh LLC}

_{[Note - EPA has proposed a new annual rate of 24 pounds ai per year – see Nov. 2017 Ask the Expert.]}