Non-native Willows like the weeping and corkscrew/curly forms are unfortunately vulnerable to several pest and disease issues in our climate because they prefer cooler summers. We don't see an obvious cause of dieback in the photos, but fungal or bacterial canker pathogens can infect willow twigs and branches, and many insects, including some willow specialists, can chew leaves. We see what looks like some leaf spot (a general term for the symptoms of many leaf-infecting pathogens) alongside some chewing damage, both of which are fairly typical of late-season willow foliage (and many shade trees in general).

There is no remedy for any of the above ailments: canker cannot be cured with fungicide; leaf spots are minor despite being a cosmetic eyesore and similarly cannot be cured with fungicide; and the leaf-chewing insects won't cause the tree any serious harm and can be ignored. If branches or twigs are dying (not just losing leaves early, but actually drying out and dying), they should be pruned off. Well-established trees can also be evaluated by a certified arborist who can look for sources of tree stress in addition to helping make a diagnosis.

Prior drought stress is still a possible underlying factor, though probably not the only issue in this case. Despite recent heavy rains, central Maryland is still under drought status given our significant shortfall of rain for the first half of the year or so. Much of Montgomery County, for example, is still in "severe drought" status as per the linked map (which is updated every week or so). Willows don't require constantly damp soils, but do appreciate even soil moisture and would do best if periodically irrigated during periods of insufficient rainfall. We provide guidance about monitoring plants for watering needs if it's helpful for the future.

Miri