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The Joy of Gardening

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Cooley Spruce Gall Adelgid

Cooley Spruce Gall Adelgids


Attached are photos of a spruce that is along my driveway in Glenview. It has a peculiar spiral pattern of tip dieback. I've looked at the tree and see no insects or insect damage. Any thoughts? Could it be salt or possibly chemical damage or overspray? I doubt at this late date that it would be cultural.

And I am wondering if there is any hope of it coming out of it and looking good as most of the top is damaged. Should the tree be removed, and a different type of tree planted there?


Judging by the pictures you have provided I do not think it is salt damage, if you see where the damage is in relation to the road and/or driveway, this does not correlate. Although drift damage is always a possibility I do not believe this is the case. It appears to be a case of Cooley spruce gall adelgids. This is an insect that commonly affects spruces and in particular the new growth on spruces. The picture shows all damage being restricted to the new growth at the tips of the branches. Cooley spruce gall adelgids can also be localized to certain areas of the tree and are more commonly found on the north side, or the shaded side of the tree. Although these insects cause some very unsightly damage they generally do not harm the tree. It would take a very heavy infestation to retard the growth of the tree. Galls are oftentimes mistaken for seed cones which might explain why you were unable to detect any insects or insect damage. Once the browning occurs it is too late to treat the insects, the browning signifies that the galls have dried out and the insects have gone. There are treatments available but these would need to be applied in late fall or else early spring, although personally I recommend resisting the urge to spray. Oftentimes these insects will cause cyclical damage and not be a problem the following year. And be assured the new growth on your spruce will eventually replace the dead brown patches. A word of advice, do not plant a Douglas-fir nearby as the Cooley spruce gall adelgids actually require both of these plants to complete their life cycle.

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