Question
We have a small cedar tree (perhaps an arborvitae?)) that has inch size "things" growing off the branches. The nodules are sectioned into about four or so sections, they are a brownish-purple, round, with bright yellow spikes on them. Are these insects? There are 4 of them, three appearing in the last two weeks. Are they harmful to the tree? Will they spread?
Sincerely,
Kris Knapp

Answer
What you describe is cedar apple rust. Normally it is a small green or brown ball on the cedar limbs but in the spring it puts out a fruiting body (the jelly looking substance) and produces spores that will travel with the wind to apple trees. Here spores are produced and they travel back to the cedar trees. It does not harm the cedar but will put spots on the apple leaves and fruit. Any disease called a "rust' takes two host #in the case cedar and apple# to complete its life cycle. It only effects cedar and apple trees.
Here is a web link that describes cedar apple rust and its control.
http://ohioline.osu.edu/hyg-fact/3000/pdf/3055.pdf