Unless this is some powder, it appears to have a fungus disease. Perhaps others can advise what to use, but I'm afraid these leaves are goners.

https://extension.colostate.edu/topic-areas/yard-garden/powdery-mildews-2-902/Powdery mildew. Salvia don't like to be wet on their leaves. Water below leaves. I don't know if you can treat for it, but take away the conditions creating it and maybe the plant can outgrow it. No more water on the leaves if you can help it. Water from below. Humidity is a killer. Keep air circulation around your plants, don't let them get smothered by weeds, etc.

Remove the infected parts. Don't over fertilize. Get the kind of fertilizer for encouraging blooms and use the LOWEST amount possible, or less.

Thanks for the advice. That seems to be what it is. We have had some heavy rains and where my sprinklers are they end up getting the salvia. I’m going to adjust my sprinklers and see if that helps. Fingers crossed it stays alive!

Actually, PM spores are killed by water, so watering on the foliage should not be an issue. It tends to be a weather/environmental problem, when soils are dry but there is a high dewpoint or high humidity. btw, I water all my plants wth a sprinkler or waterwand - the leaves are often wet and PM is virtually nonexistant, as I try not to let the soil dry too thoroughly beween watering

It is also possible that this is fertilizer residue from the greenhouse or nursery where it was grown. That will also rub off easily and typically will make white splotches on any leaves as it dries.

My experience is also that it tends to form with high dew points and dry soil. I generally whack back plants with diseased foliage and dispose of it in the trash rather than compost, either at the time if it really bugs me so fresh foliage can regrow, or at the least at season’s end so disease spores are less likely to winter over in such quantities, though I am fairly sure that PM is widespread in the environment, just waiting for the right conditions and a susceptible plant.