Hi Margaret,

Thanks for contacting the UVM Master Gardener Extension Helpline and sharing details about your lilacs and dogwood trees. Sorry to hear about the issues, it’s been a common complaint this year.

LILACS

Your timing of leaf browning matches what many gardeners experienced last year and unfortunately, again this season. The unusually wet and humid spring created ideal conditions for fungal disease development. As plant pathologist Dr. Ann Hazelrigg from UVM explained, the most likely culprit is lilac fungal leaf blight. Symptoms begin as brown spots at leaf edges and progress to curling and leaf drop. There is a bright spot, if the bark remains healthy and terminal buds are intact, the shrubs should recover fine.

UVM Extension recommends the following:

• Rake and destroy all fallen leaf debris this fall to reduce overwintering spores.

• Thin the shrubs during winter dormancy to improve airflow and reduce humidity inside the canopy. Remove whole branches from the base—avoid cutting tips, as this will eliminate next year’s flower buds.

• For more guidance, please see:
  Lilac Pests (Hazelrigg, UVM Extension)
  https://www.uvm.edu/extension/news/lilac-pests Ask Extensionplantpathology.ca.uky.edu+4The University of Vermont+4Ask Extension+4

• Info on pruning Lilacs: https://extension.umaine.edu/gardening/2023/04/04/how-do-you-prune-a-lilac-that-has-grown-out-of-control/

DOGWOODS

Without a photo, it's difficult to be definitive, but the pattern you describe is consistent with dogwood anthracnose or one of the other diseaases in the info below. It causes leaf spotting, blighted foliage, and twig dieback over time.

For reference, here's a helpful overview:

• Dogwood Diseases Overview – Penn State Extension
  https://extension.psu.edu/dogwood-diseases University of Vermont+13Penn State Extension+13Ask Extension+13

• Dogwood Anthracnose – West Virginia University Extension
  https://extension.wvu.edu/lawn-gardening-pests/plant-disease/landscape-tree-disease/dogwood-anthracnose Ask Extension+5University of Vermont+5Hortsense+5Ask ExtensionWVU Extension+2University of Maryland Extension+2

Suggested steps:

• Remove and discard dead leaves and branches, especially in fall.

• Prune out affected twigs during dry weather to reduce the fungal load.

• Improve airflow, avoid mulch piling at the trunk, and water only at the base during drought.

• If needed, especially in spring, fungicide treatments can be applied at bud break and repeated throughout favorable conditions.