Several types of pine and fir trees grow throughout California, from the Tahoe region to Southern California. Pine trees in California experience fungal diseases that are often brought on by weather or poor siting on the part of the gardener. Some diseases can be lethal if not caught and managed while others affect the cosmetic appearance of the pine.
A relatively new pine disease caused by the fungus Fusarium circinatum, pitch canker was first discovered in Santa Cruz county in 1986. It affects all types of pine and Douglas fir trees. Affected trees develop lesions on their bark that restrict water flow. As a result, needles turn brown and then red. The limbs that have lesions die; the tree may die if severely infected. Trees in central and Southern California experience this disease more frequently because of their warmer climate. This disease can be managed with careful pruning of all infected parts, and trees may recover.
Warm, moist weather and humid conditions can promote the growth of fungi that cause needle cast. Elytroderma, lophodermella, lophodermium, phaeocryptopus, rhabdocline and rhizosphaera fungi can cause this disease. Affected pines develop black or brown spots or streaks on their needles. Branches that are severely infected can die back at the tips. The University of California, Davis suggests pruning to open up the pine tree canopy and removing lower branches to reduce humidity.
Root, Crown and Collar Rot
The phytophthora fungus can cause root, crown or collar rot in California pine trees. The fungus remains in the soil, so avoid planting new pines in places where old ones have experienced root rot. The best precaution is prevention by planting in well-draining soil. Symptoms of root, crown and collar rot include wilting or browned leaves, dieback of branches and discoloration of pine bark. Affected trees will eventually die.