SiNguyen

Thanks Aldevaux! your input was helpful to me too, as well as the article by Thomas J. which I had seen before.
Watchndshy, I do a few more things that might be helpful for this problem too, and that is:
1. Treat for aphids and ants, because they spread this fungus around too.
2. Don't water in the evening and don't water on the leaves.
3. Keep tree in full sun.
4. Pick off all yellowing leaves as soon as possible.
5. Fertilize tree well, to include more iron and other micronutrients.
If your elm tree is weak, like infested with ants and aphids, not having enough sunlight or starving for NPK and micronutrients, then it will get this dreaded fungus.
In the last few years I haven't had to use fungicide at all.
Good luck to you.
Si