Rhizosphaera is a fungus
The Rhizosphaera fungus attacks spruce trees in Missouri. The disease is encouraged by poor air circulation and high humidity. This disease does not usually kill trees, but they may become largely defoliated and unsightly.
✓ What trees and shrubs are affected?
- Spruce trees, mainly Colorado blue spruce and white spruce.
The needles change to a purple color between August-November. Eventually, the needles will brown up and are cast off the tree. In most cases, the fungus will show up on one year and older needles in mid to late summer. It is common to see an infected spruce tree with only the current year’s growth on the branch tips.
- A good sign of a spruce tree suffering from rhizosphaera is the presence of black stomata on the needles, viewed under a hand lens. Spider mites may also be apparent on rhizosphaera infected spruce trees but this is a different problem. Spider mites do not cause purpling of needles.
Trees suffering from other environmental stresses, such as drought, poor drainage, trunk wounds, etc. are more likely to develop rhizosphaera needlecast. It is always recommended to maintain the health and vigor of trees to avoid fungal infestation. If rhizasphaera is identified early, pruning off and disposing of the infected branches may solve the problem. Careful sanitation of infected needles is important to limit the spread of fungal spores to uninfected portions of the tree. After pruning, sheers should be cleaned with denatured alcohol before use on healthy trees. Because spores are spread through water, avoid pruning when foliage is wet. A Chemical fungicide may be sprayed in spring when needles are half elongated (early May) and again when fully elongated (early June). – See more at: http://hansenstree.com/services/rhizosphaera.php#sthash.pBClsnjX.dpuf