I have a large poplar tree and the leaves are turning yellow then brown and falling off. This happens every year in the fall but this is July and the tree is losing leaves. Is this the sign of a problem with the tree. It is very close to my house (30 ft.) and I do not want to take the risk of the tree falling.
The signs of pre-mature leaf drop that you describe could be the result of water deficit (drought stress).
Poplars have a high water demand and if you are having a heat wave or drought, you may need to deep irrigate heavily to save it.
There are possibilities for pest and disease issues, but the drought stress is most likely.