what did you expect the sprays to do .. make the leaves all green and pretty again ... it wont.. and it didnt ...

lilac are subject to mildews ... you dont have to do anything ... it ebbs and flows over the years ...

if you want to do something.. you already did.. twice ... so no need to keep doing it ...

it will go away.. when the leaves fall off in fall.. it wouldnt hurt to pick them all up ... so the spores arent there next spring ...

btw: if you have night time lawn irrigation.. set it so it doesnt wet the leaves in the dark.. and that will reduce mildews ...

ken

flip to the ALL side for links .. and note.. white mildew turns black after treatment ...

https://duckduckgo.com/?t=ffsb&q=lilac+mildew&iax=images&ia=images

Thanks Ken! Do you know if it is lilac baterial blight?

Due to sun light reflection in my previous pictures, the leaves look like have white power. But there is no white power. I am taking more pictures and send over. Please help.

Fungicide doesn't return the infected leaves to green. It protects leaves from getting fungus. So anything already fungused stays ugly.

Call me crazy, but the leaves look too shiny to be lilac? Yes, sometimes fungicides are used to help curb fungal,stuff, but it is common for any shrub meant to get more sun than it is getting or plant for that matter, to get a little mouldy. Some plants don't react well to sprays, spraying should be avoided in full sun conditions.

Thanks all. The plant has white cone shaped flower in April-May (I am in Long Island, New York). The flower is clustered and has very strong sweet fragrant. I have two more trees which have similar shaped flowers but their color is purple. The while one has much stronger fragrant. If it is not lilac, what is it? Thanks!

Is it going to die? I might have made a mistake by spraying it around noon during full sun :(

Just try to avoid doing that in the future. Spray in the early morning or while it’s overcast.