Q: I have several young cryptomeria trees. A couple of them have branches that have turned reddish brown.
A: Cercospora needle blight, caused by the fungus Cercosporidium sequoiae, is a common disease on species of juniper, arborvitae, and dawn redwood. The first symptom is a browning of the needles in the lower tree next to the stem. The disease slowly spreads upward and outward until, in severe cases, only the needles at the tips of the upper branches remain green.
In a general way, these symptoms mimic those caused by severe stress where the interior needles turn yellow and fall off. Fruiting bodies of the fungus appear as tiny, greenish pustules on the upper surface of the needles or on small twigs. Spores are present throughout the spring and summer and are spread by wind. Infection usually occurs during periods of wet weather.
Cercospora needle blight can be controlled by spraying with copper fungicides (click for sources). There are no fungicides registered specifically for the disease but most ares registered for general use on ornamentals. Spray plants at 10-day intervals from bud break until new growth matures.