I'm curious about these -- are they very effective? There are a couple that I have seen mentioned -- Serenade and Southern Ag "Garden Friendly." I am mostly familiar with Copper Soap and (homemade) Bicarbonate of soda spray. BTW, one of the most effective changes I've found in spraying is to use a "real" spreader-sticker as opposed to homemade with detergent, cooking oil, etc. That really made a big difference for me. The selling point to me for the biological sprays is that at least some of them are (supposedly) fungicidal -- they actually kill the spores rather than just preventing them from attaching/growing.

Also, does anyone use a biological fungicide in combination with any other type?

Actinovate is one that I use early, as a prophylactic. Later I switch to potassium bicarbonate, or copper, if things get really bad.

I have used milk with pretty good success. It is not a sure thing but if started early and applied in the direct sun, it works well.

Milk at a ratio of 1:9 parts with water is very good against mildew.

I also use Actinovate and the results seem good but I never used a control plant that was not sprayed so I can't say for sure.

Sodium Bicarb in water as a spray works the same as milk but it does not kill the spores, it raises the pH and makes it unsuitable for mildew growth. You need to re-apply after rain though.

Does milk kill fungal spores -- lactic acid or such?

It is said to be an antiseptic which kills the spores when the milk interacts with the sun. I use a 50/50 spray.

https://www.growveg.com/guides/using-mi ... ry-mildew/