Last year (2012) we had a severe drought in my area. I have 5, 14 year old tulip poplars. We watered them last year and they survived the drought. This year we have had a lot of rain and and extraordinary cool summer.

Last year two of the trees developed a case of scale (one worse than the other). My nursery person told me to spray the trees with Horticulture oil before they got leaves this spring. I sprayed all of the TPs and I believe this has solved the scale problem.

However, all of my tulip poplar trees have leaves that are yellow-tinged and a little folded. They aren't losing leaves yet and there are patches of really green healthy leaves. Is this a new problem, leftovers from the drought or horticulture oil spraying this spring? Something else?

If I left out some important piece of information, just let me know and I will try to supply it.

Thanks in advance for any help/advice.