Active localized foliar and needle disease outbreaks currently occurring in northwestern

Red band needle blight, Humboldt Co. By C. Lee, Cal Fire.

On planted pines along roadsides (especially Monterey X knobcone pine hybrid widely planted by Cal Trans within the last 50 years), symptoms from red band needle blight (Mycosphaerella pini/ Dothistroma pini) flared up after December rains. Symptoms manifest as widespread needle loss in the lower half of the crown. The pathogen parasitizes pines planted in sites where they are not well adapted to conditions, eventually killing them after many years of repeated outbreaks.

Mycosphaerella arbuticola-killed madrone leaves with new leaves emerging. By C. Lee, Cal Fire.

Seiridium branch canker on redwood. By C. Lee, Cal Fire.

Damage to redwood branches is prominent this spring, with reddish (flagged) branch tips randomly located throughout the crowns. These branches have been girdled by small cankers that stimulate a flow of resin from the damaged areas. Tiny black fruiting bodies can be seen emerging through the bark near or on the cankers. While these symptoms closely resemble cypress canker, researchers have confirmed the causal pathogen to be Seiridium spp, but have not determined the exact species causing the cankers. Redwood is a previously undescribed host for this fungal genus; therefore, it is unknown whether the damage is transient on affected trees or a long-term problem.

Wildfire intensity and tree injury can vary greatly across a landscape. Conifers die  outright when all foliage in the crown is killed. Trees that sustain lesser injuries to the crown, stem, and roots can survive, but may die prematurely if the injuries are severe. 

Conifer fire. By D. Owen, Cal Fire.

How well a tree survives is influenced by many factors, such as tree species, age, size, and vigor as well as the extent and location of injury. Most tree mortality takes place within 5 years post-fire, with most dieoff occurring the first 2 years. Fire injuries can also have longer lasting impacts on tree health and may contribute to wood decay or mortality beyond this timeframe.

Insects in the Buprestidae, Cerambycidae, and Siricidae families are principal colonizers of fire-killed or severely fire-injured trees. Some of these insects are attracted by smoke and will lay eggs on trees that are still smoldering. These insects are not considered a direct threat to tree survival because they colonize trees that are dead or dying from fire injury. Conversely, bark beetles (primarily Dendroctonus species) are more likely to colonize trees that are lightly to moderately fire injured and may kill some trees that might otherwise have survived. Bark beetle activity typically increases and may persist   

Charcoal beetle, Melanophila consputa. By D. Owen, Cal Fire.

for several years in burned areas, but rarely affects healthy trees. 

Fire injury to the crown is the most important variable influencing conifer survival. Another important variable is injury to the inner bark and cambium at the base of the main stem. Bark beetle attacks in response to injury can be an additional predictor of mortality. Guidelines developed by the USFS for gauging tree survival include evaluation protocols that range from basic (estimating crown injury and stem diameter) to more complex (also assessing cambial kill and bark beetle activity). Which variables are measured is best decided based on management goals, experience, and characteristics of the fire damage that occurred. For more information, as well as tables for determining tree mortality probability, see Tree Notes #33, Survival of Fire-Injured Conifers in California.