Gall Rusts


Pine-Pine Gall Rust (also called Western Gall Rust) - Peridermium (Endocronartium) harknessii

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Mutiple galls on pine.

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Spores produced on galls look like aeciospores but directly infect pines. This is a microcyclic rust and only aeciospores are produced. No alternate host and aeciospores infect pines - getting its name Pine-Pine Gall Rust

Pine-Oak Gall Rust (also called Eastern Gall Rust) - Cronartium quercuum f.sp. banksiana

Pine oak gall rust

Galls produced on jack pine due to pine oak gall rust.

inside a pine oak rust gall

Inside a gall of pine oak gall rust showing the woody nature of the gall. Note the lesion that is starting to develop on part of the gall. 

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Pine seedling with young gall producing pycnia. The pycniospores (spermatia) are released in a sweet fluid that attracts insects. Insects move spores from one canker with pycnia to another. If they contact the opposite mating type the pycniospores fuse with the receptive hyphae that is also part of the pycnia.

Gall rust with pycnidia

Gall rust from the field with pycnidia 

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Gall producing aeciospores (loads of yellow - orange aeciospores are produced). The gall bark is pushed off exposing the aecia and aeciospores. Often, the entire gall produces aeciospores. Aeciospores are produced in the spring (late May or early June for a 1-2 week period.

Gall rust rodent chewed

Animals often chew the galls when pycnia are out. The sweet pycnial fluid filled with pycniospores attracts insects (as well as squirels and rodents)

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Red oaks are the alternate host. Small leaf sopts develop but cause little to no problem on oak leaves. Uredinia (small yellow circlular areas) are produced on the lower surface of red oak.

pine oak gall rust uredinia

Uredia producing urediniospores on the bottom of a red oak leaf.

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Telia on lower surface of red oak leaves. Telia are brown hair like structures. They consist of teliospores. The teliospores produce the basidiospores that reinfect pines.

pine oak rust telia

The telia, brown hair-like structures, on the bottom of a red oak leaf. The white powdery appearance on the telial columns are basidiospores.


Fusiform Rust caused by Cronartium quercuum f. sp. fusiforme

Fusiform rust

Fusiforn rust causing a spindle or fusiform-shaped gall on southern pines such s loblolly and slash pinesl.

Pycnia Fusiform rust

Pycnia, formed soon after infection, produce pycniospores. Pycniospores are form in a sweet fluid attracting insects. Insects move the pycniospores to another infected pine with the opposite mating type.

Aecia of Fusiform rust

In subsequent years after fertiziation by pycniospores from the opposite mating type, aecia form on the fusiform gall producing aeciospores. Masses of aeciospores are produced on the gall. These spores infect red oaks leaves.

uredinia on red oak leaves

The red oak group of species is the alternate host of Fusiform rust. Uredinia, very small yellow fruiting bodies, form on the lower leaf surface.

Uredinia of Fusiform rust

Uredinia produce urediniospores on oak leaves.

Red oak alternate host for Fusiform rust

Later in the season, telia form on the bottom of red oak leaves. All oaks in the red oak group are susceptible.

Telia of Fusiform rust

Telia, brown hair-like structures, form out of the old uredinia. The teliospores will produce the basidiospores that reinfect pine.