The Q&A Archives: Thuja occidentalis 'Yellow Ribbon', 072915

Question: As the cold season approaches (Zone 7), my yellow ribbon--purchased in March of this year from The Barn Nursery in Chatta, TN--is dropping its foilage from the inside out. It is about 1/3 gone and I do not know what is wrong with it. I planted it with more than the usual amount of top soil in a very large hole because the surrounding ground is the backfill for the new house--mostly clay and rocks.
I put in 13-13-13 fertilizer with the planting and again in May and then in August. It has never lacked for water and receives all day sunlight. I mulch with pine needles. It has grown a foot and was looking great until late Sept. The leaves from the trunk out have been dying off increasingly. I used Seven's dust on it twice this summer because of Japanese bettles and it did not appear to be damaged.
Any advice? Rebecca

Answer: Thuja can be subject to spidermite damage so I'd check first for these pests before doing anything else. Spidermites leave webbing where the leaves meet the stems. The insects themselves are tiny (like a pepper flake) so identifying them without a magnifying glass can be difficult. Hold a piece of white paper under the inner branches and tap the plant sharply. Lots of debris will fall on the paper - look for tiny moving specks. Spidermites can be controlled with chemical sprays. To keep them from showing up year after year, occasionally hose your thuja off during the hot summer months. (Spidermites like hot, dry, dusty surroundings.)

Best wishes with your landscape!

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