| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Rhabdocline Needlecast |
During March through May, yellow spots form on
the previous years needles. These enlarge and become reddish-brown
patches on an otherwise green needle. These needles then fall. |
Rhabdocline pseudotsugae
and R. weirii |
Place plants in locations where good air circulation
is available. Maintain good weed control so that air circulation
is not impeded. When approximately 10% of the buds have broken
in the spring, apply a fungicide. Repeat the application 1 week
later and again 3 weeks after bud break. |
| Swiss Needlecast |
During March through June, the previous year's
needles gradually brown and fall. Rows of tiny black fungal
fruiting structures line the midrib on the underside of the
needles. A magnifying glass is needed to see individual structures. |
Phaeocryptopus |
Place plants in locations where good air circulation
is available. Maintain good weed control so that air circulation
is not impeded. When new shoots are 1.5 inches long, apply a
azoxystrobin, chlorothalonil, or mancozeb. Repeat the application
3 weeks later. |
| Twig Blight |
A very few twig tips curl downward, turn dark
brown, and die. Only 3-4 inches of branch are affected. |
Diplodia |
Prune and destroy blighted tips. |
