My syringa reticulate “Ivory silk tree has dead branches & wilted leaves. Could this be verticillium wilt? If so, how would I treat it?
We are having a very dry summer so is it possible that it needs a good rain? Should I fertilize it and with what numbers should I use.
In recent years Syringa reticulata “Ivory silk” has become a pretty popular tree. This lilac is considered to be low maintenance, which may contribute to its popularity. It appears you have identified the two most likely causes of the problem with your tree. Apparently this May and June, in southern Ontario, have been the driest since 2005. The two most recognizable symptoms of a drought stressed tree are wilt and leaf scorch or dried out leaves. Not dead branches. To keep your tree healthy and give it a fighting chance you should really water regularly during dry weather. We tend to neglect watering trees. It is true that verticillium wilt causes wilting and premature leaf drop on plants. This disease may kill one, several or all the branches of a tree. However, lilacs are not particularly susceptible to this soil born fungi. To prevent be sure to remove plant debris from the area under the tree and rake leaves up in the Fall. Do not use infected plant material for composting.
There is another possibility – the lilac borer. Larvae of the lilac borer tunnel in the branches causing wilting especially on drought stressed trees. Severely infested branches will break off. Once again it is imperative that you remove and destroy infested stems and branches. It would be a good idea to fertilize as well. (See link below for article on Fertilizing Trees and amounts). Any application of fertilizer should be done in the spring.
Depending on how much you cherish your tree it may be worthwhile calling in an arborist. Visit the Landscape Ontario website at www.landscapeontario.com to find a company or search Yellow Pages online for arborists.