Western gall rust

What it is

A fungus that makes galls on pine branches and stems

Trees affected

Two- and three-needle pines, such as Scotch, lodgepole, ponderosa and Jeffrey pine

Where in our area

Pines at any elevation, from valley yards to the Tahoe slopes

Key sign

Round or pear-shaped woody galls; orange spore masses in spring

Greatest risk

Galls on the trunk of young pines

Western gall rust does not need a second host. It spreads from pine to pine. The USDA Forest Service says most two- and three-needle pines in the West are susceptible. This page covers what to look for, which pines, what an arborist checks and when pruning or removal is the answer.

What does western gall rust look like?

The galls are the clue: round to pear-shaped, woody swellings on branches or the main stem. The Forest Service says that in spring they release orange spores that infect new growth. Dead needles beyond a gall show where the branch has been cut off by it.

Branches that have been girdled by secondary infections turn bright red, which is how aerial surveyors find the disease. On the ground, look for bare tips on branches with a gall behind them.

• Round, woody swellings on branches or trunk
• Orange spore masses in spring
• Dead branch tips beyond a gall
• Red or brown flagging branches

Which pines and which elevations?

The Forest Service describes the host group as two- and three-needled pines, the group that includes lodgepole, ponderosa and Jeffrey pine in the Sierra. The Forest Service's list of pests for Scotch pine includes western gall rust too. That covers many yard pines, from Austrian pine in a valley windbreak to Jeffrey pine and lodgepole pine at Tahoe.

Elevation is not what decides it. The disease needs a susceptible pine and a damp spring, so it can show up on Reno lots at about 4,505 feet or on Incline Village lots at 6,437 feet. We make no claims about how common it is here; the Forest Service evidence we read is from Alaska and the Rockies.

What does it do to the tree?

The Forest Service says the fungus usually does not kill branches directly. Instead it opens the way for secondary insects and fungi that can girdle branches or boles. Main-stem galls are the most damaging form, especially on young pines: they can cause top dieback, become entry points for decay fungi and often become points where stems break.

A pine with a gall on a side limb is a cosmetic problem and a modest one. A pine with a gall on the trunk is a structural problem.

What does an arborist check?

The arborist looks at where the galls are, how many there are and how big they are, and whether any are on the trunk. They check the top of the tree for dieback, the bark around galls for cracks and decay, and the tree's overall vigor, since stressed pines draw beetles; see bark beetles in pines.

• Galls on branches or the main trunk
• Top dieback or a bend at a trunk gall
• Cracks or decay around a gall
• Overall vigor and beetle signs
• What the tree would fall on

When is pruning or removal the answer?

The Forest Service notes that homeowners can prune infected branches to reduce spread. Cut the limb back past the gall, to the trunk or a side branch, and do not leave stubs. On a tall pine, or any cut you cannot reach from the ground, it is crew work.

A trunk gall on a young pine, a top that has died back behind a gall, or a trunk that has bent or split at one are reasons for removal. Heavy galling on an otherwise declining pine is another. Large pines near a house are often crane-assisted removal jobs.

What does Battle Born Tree Service do about western gall rust?

The free estimate is where this gets decided. We assess the tree in person, and the arborist's call is one of pruning out galled branches or removal. We hold a Nevada Business License (#20131580674) and are fully insured, and two of the eight crew members are ISA Certified Arborists (WE-11728A is one person's credential). We identify the problem, prune out dead or hazardous wood and remove trees that cannot be saved; we do not spray, inject, fertilize or apply products.