The Q&A Archives: Galls on Spruce and Cedar Trees

Question: I have cedar trees in my yard that are plagued by cancerous growths ranging in size from a pea to a hand ball. In the spring (mid april)orange,slimy, fingerlike projections about 1/" to 1/2" long erupt from each gall (on cedars only). The growths are actually living plant material. When I remove them, I slice them open where I find a tiny orange worm which has burrowed into it and seems to over winter inside its protective cover. I believe the worm is actually causing the trees to develop these growths perhaps through some sort of secretion. I've tried pulling them off manually, but each year they seem to mutilpy geometrically. Now they are spreading to my norway spruce trees, attacking the new growth causing deformed candles. How can I eliminate these things? I've tried spray, but it might have been applied at the wrong time of year (summer). I need to kill the worms (moth larvae) when they are not protected within the growths. Bear in mind, the trees are about 12ft. tall and there are about 40 trees, a systemic seems impractical.

Answer: I think the cedars are actually suffering from a disease called cedar-apple rust. It's a fungal disease that requires two host plants to complete its life cycle -- cedars and apples -- hence the name. I don't think there is a systemic solution to this particular problem.

The description of the gall-forming insects sound like adelgids. Different species attack various species of spruce. The insects are exposed only for a short time. Females lay eggs on buds at about the time buds start to break. They surround their eggs with a wooly substance to protect them. The eggs hatch within 10 days, and as the nymphs feed, a gall forms and eventually surrounds them. They do appear orangey! The galls break open naturally to allow the maturing adelgids to leave, and they in turn lay eggs that will overwinter.

Timing sprays is crucial to control. Since this is a large planting, I suggest that you enlist the aid of a professional arborist. If the solution is a systemic pesticide, they may use products that only licensed applicators are allowed to handle. If you want to try it on your own, consult with your county forester for details on what to look for and what to apply. Your extension service (ph# 908/788-1338) can help you reach a forester. Best of luck!

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