I had significant issues with psylla with my seed grown persimmons last spring on my deck. By the time I recognized it, I had a lot of damage. I used Sevin and uncurled slightly curled leaves. I completely removed any heavily curled leaves or those that dried out.
I knew what to look for this year. I did two things. At the first sign of anything white on the leaves, I sprayed with Sevin. I also put out a bug zapper near the trees in hopes it would attract and remove any adults before they could lay eggs.
So far, the problem is significantly reduced from last year.