It seems to be one of the most common complaints this spring: my spruce tree is turning brown and dropping needles!!!!
I’ve talked to a lot of experienced arborists about this issue and although it would be convenient to blame it on a new disease, in most cases, it seems more like a complex set of factors are responsible.
- 2013 had an extended period of hot/dry for nearly 6 weeks in late summer, we hit 40 C on a few days (remember that?), many of our larger evergreens are routinely planted in poor soils with little aeration and drainage
- We started to see decline in established spruce in fall 2013
- 2013-2014 was one of the coldest winters on record and we saw an unprecedented amount of desiccation on evergreens after that
- 2014 was cool/wet, lots of needle drop reported on landscape spruce, yet we saw very few needlecast pathogens (e.g. Rhizosphaera)
- 2014-2015 was again, one of the coldest winters on record, some say even colder than the previous year, and again we are seeing a high level of desiccation on evergreens this spring
- We saw a lot of feeding injury from yellow headed spruce sawfly on new growth for about 3-5 years now, especially north of Toronto.
- Michigan State University is reporting Phomopsis disease of spruce in some of their landscape but still only responsible for a % of the spruce decline they are seeing. Phomopsis is thought to cause branch dieback from the basal branches, up to the top. But we are seeing all kinds of patterns of symptoms in the landscape.
- We have seen some Cytospora-like canker (branch canker), largely unconfirmed by laboratory diagnosis but again, only a % of what is being linked to spruce needle drop in the landscape
Most arborists I talk to don’t think its any one thing but a combination of factors, especially climate and site conditions. As an explanation, that’s a hard sell to your concerned clients. Services that increase soil aeration and drainage plus the addition of organic matter will help surviving trees recover and give them a better chance to thrive in the coming years.
It would be really interesting to look at the root systems on these symptomatic trees and examine them for structural issues etc.
If you see weeping cankers on the symptomatic branches on spruce trees, try submitting a sample to the University of Guelph Pest Diagnostic Clinic in Guelph and have it tested for plant pathogens such as Phomopsis or Cytospora.