Can you tell if this is needle cast from this picture?

John_KAYS

Well-Known Member
Someone sent me this picture and I can’t quite tell for sure if this is needle cast. I know sending a sample into a lab would be recommended, but I am just curious what you all think. This tree also has bag worm on it... Thanks!
58804
 

KTSmith

Well-Known Member
I'm not seeing enough of the symptoms. I don't grasp the gravity of the situation. That sounds mean, but I don't intend that. In a managed landscape, pruning the lower bole makes sense. The foliar necrosis? I'm not noticing it enough to respond in depth.
 

JD3000

Most well-known member
Colorado spruce are difficult if not impossible to keep around here without human intervention. Sometimes poor drainage alone is enough to do then in.
 

ATH

Well-Known Member
Not enough bagworms on there to do that much damage...but if they pulled a bunch off, that could have been a significant contributor.
 

jed1124

Active Member
Needle cast will generally have purple needles with spores running along the stomata on the underside of the needle.
Check for swollen black canker near the branch collars, could also be cytospora.
 

John_KAYS

Well-Known Member
I'm not seeing enough of the symptoms. I don't grasp the gravity of the situation. That sounds mean, but I don't intend that. In a managed landscape, pruning the lower bole makes sense. The foliar necrosis? I'm not noticing it enough to respond in depth.
Yeah, I haven't seen the tree yet in person, but it didn't look terrible to me from the photos. I know in this area the Colorado Spruce don't do that well in general. This tree is up on a property at the top of a hill. They are growing this and a few others as a windscreen and are hoping that they don't have to prune the lower branches off. I don't know how many bagworms they have pulled off, but I wouldn't think it was a huge contributing factor to the dieback. It has been a couple of very moist years...
 

KTSmith

Well-Known Member
In New England, blue spruce is especially prone to Cytospora canker after they reach some size. Enough so that no one who understands trees recommends them....although they still get planted and look OK the first few years.
I grew up with bagworms outside of Kansas City. Definitely unsightly and more. Sorry not to be more help!
 

ATH

Well-Known Member
Cytospora has always been a problem here in Ohio for larger Blue spruce too. Lately, however, the spider mites, Rhizosphaera (and/or Stigmina), and pitch mass borers combine to take them before Cytospora has a fighting chance to get in on the action!
 

John_KAYS

Well-Known Member
Thanks for all the advice. It's great to have this all to consider before I go see it in person. I am not a huge insect and disease guy so I really appreciate the pointers. I am trying to gain more experience and knowledge on this stuff. What is the best book on insects and diseases? I have the pesticide applicator training materials but I am looking for some better more specific to our industry guides that I can keep on hand. Thanks.
 

KTSmith

Well-Known Member
As for books, the two references by Comstock Publishing:
"Insects that feed on trees and shrubs" by W.T. Johnson and H.H. Lyon
and
"Diseases of trees and shrubs" (2nd ed.) by W. Sinclair and H.H. Lyon.

Having said that, I am most familiar with the Sinclair and Lyon volume. A real masterwork but... there aren't any real keys for identification, so it's a great reference for the disease biology after you have at least a tentative identification.
And of course, comprehensive texts like these become outdated. Still, that's where I go.
 

ATH

Well-Known Member
I've always liked the Christmas Tree Pest Manual:
https://www.fs.usda.gov/naspf/publications/christmas-tree-pest-manual-third-edition

By no means is it comprehensive...but it has many of the common evergreen pests with good pictures and a summary of what to look for when.

Pirone has some good books too: https://www.amazon.com/Diseases-Ornamental-Plants-Pascal-Pirone/dp/0471072494

The 2 books @KTSmith suggested are "essentials" to me...but they are tough to use. Like he said, you can confirm you are looking at what you think you see. When I am completely stumped, I will also go to the index by species. Each pest of the species is listed. It is not an efficient way to go, but I've ID many things that way over the years.
 

KTSmith

Well-Known Member
Thanks ATH, all true. Yes! the Christmas Tree Pest Manual is great for non-specialists and does hit the highlights pretty darn well. And, your tax dollars at work.
 

ATH

Well-Known Member
Should also add that I learn as much from small publications as I have from more complete books. For example, OSU Extension does the Buckeye Yard and Garden Line. Used to be weekly...now it is more of a periodically (couple times a week) updated blog format.

https://bygl.osu.edu/

Having read that for 20 years, I've picked up a bunch of new knowledge. Yes...a lot of it becomes refreshers, but I still follow it.

The other that has been very helpful over the years is now called the ONLA Plant Health Care Newsletter (was the PEST newsletter by Dr. Shetlar for many years). Again...20 years of reading that a lot has been very helpful. That is currently written by @JD3000 and, apparently, whoever else he can sucker into helping. o_O https://www.onla.org/page/PHCNewsletter
 
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