By Adam Austing, University of Minnesota Extension Educator
There are widespread reports of lilacs dying throughout Wright County and Minnesota this year. In many cases, affected plants were mature and never had noticeable issues in the past. The common lilac, Syringa vulgaris, seems to be the most susceptible. However, the Japanese tree lilac, Syringa reticulata, has shown susceptibility as well.
Weather has most likely played a significant role in the decline of many of these lilacs. In May we had a week of very cold temperatures without snow cover, possibly compromising root systems. Much of June and July were also very hot and wet, which likely increased plant stress and susceptibility to disease and other issues.
One disease, pseudocercospora, has been more present than usual this year. The main symptoms are yellowing leaves, eventually turning brown, and branch dieback. These symptoms are similar to many other lilac diseases and issues, so it cannot be assumed that pseudocercospora is the issue you are dealing with. Verticillium wilt (a fungal disease) and lilac borer (an insect) are two other common culprits. The best way to make sure you know what is harming your lilacs is to send a sample to the UMN Plant Disease Clinic (PDC). Instructions on collecting and submitting samples can be found at pdc.umn.edu.
More information on how to assess the health of your lilacs can be found at www.extension.umn.edu/yard-and-garden-news/lilac-issues-season. In many cases, a lack of previous care for the lilacs is a big contributing factor to the decline of health as well. Lilacs require pruning, debris cleanup, and oftentimes watering. Many of us are guilty of assuming that lilacs are tough and don’t benefit from added care and attention. Information on how to best care for your lilac shrub, hedge, or tree can be found at www.extension.umn.edu/trees-and-shrubs/lilacs. Of course you can always reach out to your local Extension educator as well. Residents in Wright County can contact Adam Austing at (320) 249-5929 or firstname.lastname@example.org for more information.