Many
trees in the area especially the cottonwoods are losing a lot of
leaves. Trees stressed by insects like aphids, or fungal leaf disease like venturia tip blight are really dumping their leaves at this point. In most cases, the early hot weather is the culprit. The big mature trees are dumping leaves to balance out the system. Trees with fewer leaves require less inputs like water. Well watered and fertilized trees are better able to resist heat stress, disease and insect pressure. As long as the general health of the tree looks good, I’m not overly concerned about this pre-mature leaf drop.
Raking up and disposing of the leaves is important to contain the spread of diseases like venturia leaf blight. Many of our Aspen trees are loosing leaves infected with Marssonina leaf spot.
Trees with a history of these types of fungal leaf diseases would benefit from a foliar applied fungicide in the spring of the year. Applying a good fungicide like Benlate just after the tree starts leafing out will give these new leaves protection against the invading fungus.
