Blue Spruce problem
I have several blue spruces with the branches dying from the bottom up. Looks like Rhizosphaera, but could phomopsis or Diplodia. Could you suggest an appropriate fungicide and possibly where to obtain it. Thank you. Robert Kueber at email@example.com
Alger County Michigan
The key symptom of spruce decline is branch dieback, which progresses over two to four years and renders the plant’s appearance unacceptable for most homeowners. The rapid decline of many spruce trees in Michigan and surrounding states appears to be related to an increase of canker diseases coupled with other disease and insect problems.
There are three principle types of diseases that affect blue spruce trees: needlecasts, tip blights and canker diseases.
As the name implies, trees with needlecast diseases shed needles. Needlecast fungi often infect needles on the current year’s shoots. As the disease progresses, the needles die, usually the year following the infection. As a result, trees affected by needlecasts often have an outer “shell” of live needles on current shoots and dead needles on older shoots. The two most common needlecasts we find in spruce are caused by the fungal pathogens Rhizosphaera and Stigmina/Mycosphaerella.
Fungicides that are available are preventative. Well-timed sprays can prevent new infections. Time your first application in the spring after the new growth has expanded to 0.5 to 1.5 inches in length. New growth typically appears in May. Follow-up with 1-2 additional sprays as indicated on the fungicide label. Fungicide applications will need to be applied for at least 2-3 consecutive years and maybe more. Fungicides that are labelled for control contain the active ingredients of either chlorothalonil, mancozeb or copper. Remember to read and follow the instructions on product labeling.
For more information –
What is spruce decline? http://msue.anr.msu.edu/news/what_is_spruce_decline_and_what_should_you_do_about_it