Knowledgebase
Lilacs dying #772675
Asked September 22, 2021, 12:12 PM EDT
Winona County Minnesota
Expert Response
The fungal disease Lilac Pseudocercospora leaf spot symptoms are yellowing then browning leaves, dieback. The spores of Pseudocercospora can persist for several years on plant debris (leaves, stems, dead flowers, bark. Rake up fallen leaves to help reduce the likelihood of reinfection next season. In late winter, decrease the lilac density with renewal pruning. Consistent watering will also help support the stressed plant. The first site explains lilac pruning.
https://hortnews.extension.iastate.edu/1993/2-10-1993/lilac.html
There are many reports of older lilacs suddenly wilting and dying. Please read the following sites for other disease of lilacs.
https://extension.umn.edu/yard-and-garden-news/lilac-issues-season
https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/lilac/branchesdeaddying.html
https://extension.umn.edu/plant-diseases/gray-mold-flower-garden
They could send a sample to the plant disease clinic to determine the cause of the black wilt.