According to the WA Plant Disease Handbook, Serenade has rather limited effectiveness compared to other fungicidal controls. YMMV

Personally, I like Neem oil - it is a multifunction pesticide in that it is a contact insecticide, a miticide and a fungicide. For minor home plant issues - aphids and white flies, spider mites, rose black spot, powdery mildew, etc. - it works very well. Can also function as a systemic if used as a soil drench, which expands it efficacy towards hard to control insects like scale.

As with pretty much any pesticide, organic or not, I would avoid spraying when pollinators are present.

Thank you!

Mites/Aphids/Thrips seem easier to control.

Scale & Mealybugs are harder...if need doesn't work for these, what else would you suggest?

Serenade is a fungicide so obviously of little use in controlling insect problems :-)

Scale is hard to control any way you look at, organic controls or not. Horticultural oil can have good effectiveness but you have apply at the appropriate stage in the insect's life cycle to have the best results. That's why Neem can be useful, as it is one of very few, if any other, organic controls that has systemic capabilities.

There are other biological controls for scale as well - lady beetles, lacewings and parasitic wasps - although maybe not as easy to obtain or use in a home environment.