https://articles.extension.org/pages/18351/organic-management-of-late-blight-of-potato-and-tomato-with-copper-products

Hope this article ll help you.

Many thanks for your answer Kaushik. It's a useful summary although it has nothing to say on crop uptake; and the link to their source material, 'effects on human health' doesn't work.

Thanks for your help!

David

David,

I am afraid that most of studies of copper spray on potato against Ph. infestans were done long time ago. But, there are many other crops studied for copper accumulation and effects on plant growth, like:

Article Copper accumulation in vineyard soils: Rhizosphere processes...

https://www.agriculturejournals.cz/publicFiles/04098.pdf

https://juniperpublishers.com/artoaj/pdf/ARTOAJ.MS.ID.555713.pdf

This one https://pdfs.semanticscholar.org/ee62/5bfe2abd35a9cb11cab2a84bbaa2715412cf.pdf is reporting study on beet plants which is quite similar to potato in biology and technology of cultivation.

Many thanks Alex, I shall study these closely. My intial readings suggest that there is more information on accumulation of copper in soils than on crop uptake. As we have just harvested a potato late blight trial where copper oxychloride is one of the treatments, I shall send some samples for analysis.

David

David, if you care about effect of copper treatment, you should try combinations of copper with other permitted pesticides. Sometimes it works better, but biological control agents may reduce effect by 50% or more.

Thank you Alex. In our current trial we have a biostimulant treatment containing phosphite which is showing good control against late blight. It's not permitted by organic standards however, so I can't use it on my farm which is a long-term licensed organic holding. David