Japanese silk lilac Tree


My tree is 10 years old. It has always been beautiful. This year half of the tree looks dead. I’m in Mississauga. I have a 3 year old beside that is fine. There is some growth out of the dead branches. I’ve tried watering it Some spring fertilizer was around it in my garden. What can I do


We are sorry to hear that your lovely Ivory Silk Japanese tree lilac (Syringa reticulata ‘Ivory Silk’) is suffering. We hesitate to offer a definitive diagnosis without a photograph or more detailed description of the symptoms, so here are the three most likely culprits for your consideration, with links to more information to help you narrow it down:

  • Lilac borer: the larvae of Podosesia syringae tunnel in the branches, feeding on the phloem and outer sapwood, causing the tree to wilt. After a year feeding and maturing inside the host, the caterpillars chew their way out of the host and pupate. Look for irregularly-shaped entrance holes, often with visible frass (i.e. excrement) built-up next to them; circular exit holes; and brown, brittle, empty pupal cases around exit holes. See Lilac/Ash Borer
  • Bacterial blight: Pseudomonas syringae bacteria strike in spring. On infected host trees, young shoots develop black stripes or one side of the shoot turns black; they droop and die. Leaves develop spots that gradually enlarge into water-soaked blotches; entire leaves turn black and die. Flowers wilt and darken. Infected twigs become girdled and die. See Lilac Bacterial Blight
  • Verticillium wilt: this fungus attacks through the roots and spreads upward through the xylem (i.e. water conduits) of the host tree. The infection blocks the xylem, causing wilting and premature leaf drop. Symptoms typically first show up as sudden wilting and death of one or several branches, or even one side of the tree. See Verticillium Wilt of Tree and Shrubs

All of these infestations/infections are difficult to eradicate once established; it seems that at this point you will need to focus on containing the pests/disease so that it does not affect the younger healthy tree located next to it. When removing diseased plant material, take care to practice good sanitation to prevent cross-contamination: sterilize the cutting instruments between cuts, thoroughly clean-up the site after pruning, destroy/dispose of the infected plant materials instead of composting them.

We wish you the best of luck in managing the pest/disease and saving your tree.