Aspen tree health
Hi and thank you for the advise! I live in Central Oregon, elevation 3000ft., high desert. I have a clump aspen and another single aspen next to it (different stock). They are about 10 year old and 20-30 ft tall. My clump aspen is unhealthy and the single aspen is in great shape. Last year aphids attacked the clump, I treated it and hoped it would pull out this year; no such luck. I treated it again about a month ago with Baer tree and shrub insect control, but the leaves are small, pale green to yellow, brown. Many of the leaves, although not all, have sticky sap dots on them. I'm watering it more now because I was concerned it wasn't getting enough water and I additionally pounded in some miracle grow tree stakes around drip line of tree.
Long story short; do you think the aspen has any other issues besides aphids and why would they attack one tree but not another? I don't see any aphids on the leaves by the way, so I'm hoping the sap is just leftovers, although the tree(s) is not springing back. Does anyone have recommendations to improve health? Thank you so very much, great site!!! Suzi