Spruce tree problem shows symptoms of both needlecast and branch death

Although needlecast and branch death will have to be treated in the spring, take this time to learn more about managing these issues and be prepared for what to do next spring.

Last week, we reported that all species of spruce trees, especially Colorado blue spruce, are experiencing a decline throughout the lower peninsula of Michigan (see "Spruce problems are probably caused by more than a single agent"). The problem is not caused by the new herbicide Imprelis, released by DuPont, which has been in the news lately. This needle cast and branch death problem started about five years ago and has become epidemic in the state.

As we stated last week, this corresponds to a new needle-associated fungus, Stigmina, which has been called a pathogen on other plants, but has not been proven to be a pathogen, yet, on spruce. It could also be that Rhizosphaera, a well-known spruce needlecasting pathogen, is causing these serious symptoms by itself or in combination with Stigmina. We now know that many of these trees also have Phomopsis, a canker-causing fungal pathogen known to cause branch death. We have seen spruce trees with Phomopsis canker and branch death, but without needlecast disease, and we have seen spruce with needlecasting disease without apparent Phomopsis. We are currently doing research to see if we can detect both needlecast fungi and Phomopsis on declining trees.

Most of these problems are occurring on older landscape spruce trees and many of these trees have never been treated for disease. Professional growers at Christmas tree plantations and tree plantations usually have a scripted needlecast treatment program that landscape trees do not receive. For several years, we have listed those types of management programs here, but generally have not expected landscape trees to be treated.

Because needlecast diseases and Phomopsis branch death will be managed by treating in the spring, we can take this opportunity to list articles printed in the past where the landscaper can begin to learn more about managing needlecasting diseases. Treating for Phomopsis canker will be new for everyone, even for most Christmas tree growers and tree farms. Again, treatment should begin in the spring, but we will begin to provide some information on managing Phomopsis with chemicals. Without more information being available, my suggestion is to reduce the Phomopsis inoculum by eliminating dead infected branches (lower branches with terminal bud death), and protecting healthy branches with applications of thiophanate methyl-based materials such as Cleary's 3336 or T-Methyl. Both of these materials are registered for spruce trees and cankers caused by Phomopsis. For further information, read these past articles so you can be prepared for what you may want to do next spring.

Previous articles that apply to this new spruce decline

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