Fir Broom Rust

Leaf Rusts of Hardwoods and Needle Rusts of Conifers

Juniper Broom Rust - Gymnosporangium nidus-avis 

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Juniper with witches' broom.

Juniper broom rust dry

In the spring telia start to form directly out of the branches on the broom.

Juniper broom rust telia

Dried telia (dark areas) on the branches. Note the pointed needles of the juniper broom. The rust induces juvenile needles to form which are sharp pointed needles in contrast to the smooth rounded mature needles found on the other areas of the tree.

Telia juniper broom rust when wet

When wet, the telia expand into a jelly like matrix.

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The telia contain teliospores that will produce basidiospores.

Service berry with rust

Serviceberry, Amelanchier, is the alternate host for Juniper Broom Rust.

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Pycnia are produced on top surface of Amelanchier leaves.

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Aecia are produced on the bottom of Amelanchier leaf. The aeciospores infect junipers

Fir-Broom Rust

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Melampsorella causes a withches' broom on fir. The alternate host is chickweed.

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Pycnia and aecia are produced on needles of the broom on balsam fir.

pycnia and aecia of fir broom rust

A view through the stereoscope showing a needle with pycnia (black dots) and aecia (white structures that produce aeciospores).

Chickweed with uredinia

Chickweed with uredinia. Telia will form later in the summer


Spruce Broom Rust and Spruce Needle Rust - Chrysomyxa species

Spruce broom rust

Witches broom on spruce. Pycnia and aecia form on the needles. The alternate host is bearberry (also called kinnickinnick) that has the uredinia and telia.

Spruce needle rust

Some species of Chrysomyxa attack spruce needles but do not form witches brooms. Pycnia and aecia form on the new needles. The alternate host is labrador tea where the uredinia and telia form.

Spruce needle rust aecia

Spruce needle rust can produce loads of aeciospores.