Garden Detective: the beautiful Stewartia tree
A Stewartia tree growing in reader Frank DelliSanti's garden. Credit: Handout
The arborvitae leaf miner emerges as a very tiny caterpillar that mines between leaf surfaces and eats all the chlorophyll, which is why the trees turn brown. They will bounce back if you apply a systemic insecticide like acephate, sold under the brand name Orthene, or spinosad, branded as Conserve. It's advisable to hire a tree professional licensed to handle pesticides instead of attempting this yourself. Also, you're using the wrong fertilizer on your trees: Holly-tone is for acid-loving plants; arborvitaes do best in alkaline soil. Instead, apply lawn fertilizer once a year at the rate of two to four pounds per 100 square feet.
