Do you need bonding for copper sulphate in rain?

I am using a modern version of copper sulphate, the name of the product is Cuproxat FW. I am not sure how much it is available internationally, maybe it is just a local product, but what I can tell about it is that it is made of copper 2 ions in nano form, so that the coverage is better, and the label says it has very good bonding ability, but does not mention any guidelines for rainy weather more than that. Besides, on some other websites I can read the classic Bordeaux mixture is recommended in rainy weather due to its bonding capabilities, other sites mention it only applies in certain amount of rain only.

What is your suggestion for using copper sulphate in rainy weather, shall I add a bonding agent from the shop? Shall I use simple oil only? If it can be oil, in what ratio?

This is the English version of the description of the product I referred to, by the way:
https://www.gazdabolt.hu/en/T00496-Cuproxate-FW-5-l.html

Copper sulfate is an inorganic salt that is highly soluble in water. The disassociated copper ions mainly bind to organic matter or remain dissolved in water.