Cankers of several types will infect larches. These can not be controlled chemically. Symptoms are sunken or discolored bark and dieback of the branches. Prune out infected branches and fertilize to maintain tree health.
Needle Blight causes yellow spots on the needles. The infected needles turn brown and hang on the tree. The spur bearing the needles may be killed. Gather up and destroy fallen needles to kill overwintering disease.
Several rust diseases infect larch. Alternate hosts are willow, poplar, and birch. In landscapes, larch and an alternate host may be close. Infected needles near the branch tips turn yellow. Disease identification identifies the alternate host for possible removal.