Colorado Blue Spruce blight

Asked September 18, 2018, 9:43 AM EDT

Colorado blue spruce blight? I have enclosed a picture of one of my blue spruce trees with a fugal disease as no insects have been seen on it. Should I remove this spruce and what can I do to protect my other spruce trees that currently show no signs of this condition? Thanks for any help that you can provide!

New Castle County Delaware

1 Response


Blue spruce is susceptible to a fungal needle cast disease called Rhizosphaera needle cast named after the fungus that causes it. It causes needles to drop, and affects the two year old needles on trees that are four years old or more. The fungus only affects spruce.
To control, use a preventative fungicide inn the spring, the best is chlorothalonil, available as Bravo. Prune off the worst affected branches and discard off the property. Timing is critical Spray in mid-May, again in ten days, and again in another ten days. This will protect the new emerging needles. The old affected needles will drop.. It will take you two years to get your tree back to good health.
You may want to have a tree company do the spray treatment, to get good spray coverage if the tree is large.
Thank you for contacting Cooperative Extension,