Classic sign of too much water causing a proliferation of phytophthora, a soil pathogen we have issues with in our neck of the woods. Apply AgriFos (you can buy it on amazon.com, and possibly at Andersen Nursery), 2 Tbsp. per 5 gals. Do a soil drench. Repeat in 4 weeks. Repeat in another 4 weeks. Treat every 6 months, timing the application to be in late winter/early spring when our temps are just right for this fungal-like organism to bloom. If you're seeing mildew, rust or black spot on your roses - perfect temps for phytophtora. Only water if the soil is drying out 18" down. Mulch under your tree to conserve water, keeping the mulch away from the trunk. Make sure your tree is not in grass and is not getting hit by lawn sprinklers.

Patty S.

Hi Patty, i am curious what characteristic(s) led you to the phytopthora diagnosis. Is it the yellow ribs? The upward cupping of the leaves, or the combination of both? other?
-George

This post was edited by Becauseican on Fri, Jul 18, 14 at 18:07

Hi, Patty

Thanks for your diagnosis and suggested procedures to fix
the problem.

>Mulch under your tree to conserve water, keeping the
>mulch away from the trunk. Make sure your tree is not in
> grass and is not getting hit by lawn sprinklers.

I noticed there is a small sprinkler under the tree, also the tree is close by our lawn sprinklers. Should we remove the
small sprinkler altogether?

We will try the AgriFos you suggested, hopefully to fix the yellow leaves.

David