Identify White Pine Blister Rust and Remove Cankers (Identification)

Identification
Symptoms vary with different stages of spore and canker development. The fungus has five spore forms in its life cycle: two (pycniospores and aeciospores) occur on pine, and the others (urediospores, teliospores, and basidiospores) occur on the alternate hosts, currant and gooseberry (gibes) bushes. The fungus cannot spread from pine to pine.

For initial infection look for: Patches of browning bark bordered by a yellowish discoloration of the bark the first year and a typical spindle-shaped swelling by the second year after infection. Fungus spores (basidiospores) produced on the Ribes host during cool, wet weather in late summer and fall infect the white pine through stomata on needles or young stems.

Breaks in the bark cankers and a resulting resin flow down the stem that hardens, providing a distinctive symptom.

Do not confuse with damage done by the pine bark aphid which appear as scattered patches of white flecks on the bark of the tree. Year round look for: Mature cankers bordered by a yellowish discoloration of bark at the canker margin and rodent-feeding on cankers.

In early spring look for: Sporulating cankers in the form of orange-yellow blisters that push through the bark and produce aeciospores. These spores are wind disseminated and infect Ribes.

In late spring and early summer look for: Pycnia that appear as yellow-brown blisters on the canker face and produce a sticky yellow-orange fluid containing pycniospores. After a short time these blisters and fluid turn hard and black and can persist in this form for several weeks. In summer look for: Uredia on Ribes. Orange spores, called urediospores, develop on the undersides of leaves as a result of infection by aeciospores released from pine, or from previously produced urediospores that can re-infect the same host, but cannot infect pine. These spores are wind disseminated.

In late summer and early fall look for: Brown hair-like projections (telia) on the underside of Ribes leaves. Telia commonly start forming while uredia are present on the same leaves. In cool, wet weather of late summer and early fall, the telia produce delicate round, hyaline spores called basidiospores that are carried by wind to pine needles where they cause infection thus completing the life cycle.

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Identification Symptoms vary with different stages of spore and canker development. The fungus has five spore forms in its life cycle: two (pycniospores and aeciospores) occur on pine, and the others (urediospores, teliospores, and basidiospores) occur on the alternate hosts, currant and gooseberry (gibes) bushes. The fungus cannot spread from pine to pine.
	For initial infection look for: Patches of browning bark bordered by a yellowish discoloration of the bark the first year and a typical spindle-shaped swelling by the second year after infection. Fungus spores (basidiospores) produced on the Ribes host during cool, wet weather in late summer and fall infect the white pine through stomata on needles or young stems.


Breaks in the bark cankers and a resulting resin flow down the stem that hardens, providing a distinctive symptom. Do not confuse with damage done by the pine bark aphid which appear as scattered patches of white flecks on the bark of the tree.		Year round look for: Mature cankers bordered by a yellowish discoloration of bark at the canker margin and rodent-feeding on cankers.


In late spring and early summer look for: Pycnia that appear as yellow-brown blisters on the canker face and produce a sticky yellow-orange fluid containing pycniospores. After a short time these blisters and fluid turn hard and black and can persist in this form for several weeks.		In summer look for: Uredia on Ribes. Orange spores, called urediospores, develop on the undersides of leaves as a result of infection by aeciospores released from pine, or from previously produced urediospores that can re-infect the same host, but cannot infect pine. These spores are wind disseminated.