Our blue spruce tree has orange discoloration on its needles which makes the...

Asked August 17, 2013, 12:01 PM EDT

Our blue spruce tree has orange discoloration on its needles which makes the entire tree look orange.. I see no insects. The discoloration is powdery and has a round spore like appearance on the needles. These "spores" are about 1 millimeter in size and cover the entire needle. Some of the needles are falling off.

St. Louis County Minnesota

1 Response

The tree seems to be exhibiting symptoms of spruce needle rust. It's caused by fungi from several species of the genus Chrysomyxa.

You can learn about the disease at this website:

Spruce needle rust
http://www.extension.umn.edu/distribution/horticulture/M1265-3.html

If the problem is severe, consider using a fungicide recommended in this bulletin:

Weir’s Cushion Rust or Spruce Needle Rust
http://plantclinic.cornell.edu/factsheets/chrysomyxaweirii.pdf