I need help with lilacs

[KevinS]

In our area,southern ontario a lot of Syringa reticulata "Ivory Silk Lilac" have been declining and dying whole branches die back and we can't figure out a cause or treatment we've the local university run. Any test that they or we could think of and nothing.

It looks like winter die back but its not. Anyone else in a similar situation? Any ideas? I will try to get a list of tests ran asap

Thanks

 

[treeness]

Wheres the location? A lot of them are planted as boulevard trees with poor compacted soil, and the only water they get is from the rain. With the lack of winter run-off and the way our summer has been going, a lot of trees are starving for water. Sometimes it could be just that simple. It could be just shutting down certain parts to deal with the heat. But the location and site characteristics are a something to be known before a recommendation can be made.

 

[mrtree]

What your likely seeing is a wilt-like disease caused by an oomycete such as phytophthora.

You need to seperate from verticillium. Unfortunatley verticillium cannot always be seem as streaking in lilacs.

Can run ELISA (Enzyme-linked immunosorbent assay) tests on wood samples, soil is no good as tests will almost assuredly be positive.

If you are cutting any down look for streaking at the root crown, this may be the best indication of oomycetes.

I am not sure that this has ever been published as a cause of wilt in lilacs but it seems quite common.

 

[KevinS]

Thanks guys these trees are street trees at different condominiums so low traffic but still rough soil.

If it is wilt disease how do you usually treat your cases?

 

[Frax]

If you can get to the roots of one, see what they look like. I've had reasons to suspect stem girdling roots in poor stock in other species. If they are all a similar age and possibly similar source, it's worth investigating perhaps. Condo trees tend to be notoriously poor stock at least in my experience in Calgary.

 

[KevinS]

Thanks Frax I'll look into that

 

[mrtree]

I imagine that you will find a whole set of issues leading to oomycetes. Poor soils are likely, run a perculation test and I bet that you will find poor draining soils.

As for management, there is likley not much. Typical methods to improve plant and soil health should be considered; mulch, compost, organic fertilizer, aeration, RCE, improved drainage (if possible), etc.

Removal and replacement is a worthwhile option, find something that can withstand the clay soils.