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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis
Rhizoshpaera Needle Cast

Spruce Tree Woes

Posted by John Fulton -

Many spruce trees, especially Colorado blue spruce, are not very well acclimated to our environment in Central Illinois. The altered growing conditions often weaken the tree over a period of time, making it more susceptible to other diseases and insects.

Rhizosphaera needle cast is one of the main diseases of spruce. Symptoms include a purple cast to needles, needle drop, and a tendency to start at the bottom of a tree and work upwards. One key to control is removing infected needles and cleaning pruning equipment between cuts. Chemical control is possible by protecting new growth with chlorothalonil fungicides such as Bravo or Daconil 2787 or manganese/zinc combinations such as Cleary's Protect T/O. These programs would probably have to be done for at least two years, and make sure to follow the recommendations on the product label.

Other diseases such as diplodia tip blight and cytosphora canker also affect spruce trees, and let's not forget spruce spider mites. Spruce spider mites have been active for a while, and will probably continue to be active with the cool weather we have had this spring. This insect damage shows up as mottled needles, and there is usually fine webbing present. Needles may also drop from the spruce spider mite. Control of the mite can be accomplished with insecticidal soap or an appropriate miticide.

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