Cronartium ribicola, a rust fungus native to China, causes this disease. This fungus needs two hosts to complete its life cycle, one from the Pinus genus and one from the Ribes genus, which is commonly known as currants or gooseberries. There is a more significant incidence of five-needle pines, especially young pines, which are more susceptible to damage. It has a life cycle between 3 to 6 years, and symptoms usually develop into irreversible damage, while the first years display moderate symptoms. This fungus prefers cooler temperatures and moist environments. There are economic effects on the timber industry since this fungus affects a vast range of Pinus, some of them considered premium materials that are ranked at higher values.
White Pine Blister Rust Treatment
Signs of damage
In Pinus:
- Yellow or red spots on the needles after 1 year.
- Elliptical-shaped cankers will appear on branches after 2 years.
- Blisters. After 3 years, white and yellow blisters will appear in springtime.
- Dead branches. Lower branches will perish. Branches above cankers will die as well.
- Trunks develop oval or diamond-shaped cankers.
- Orange and gummy droplets. Cankers develop these in summer.
In Ribes:
- Yellow leaf spots.
- Orange spots on the underside of the leaves.
- In late summer to early fall, hair-like structures, orange to brown, will form.
- Stunted growth.
- Falling of leaves during the growing season.
How to prevent
Well-drained soil, aeration between trees, and scouting for blisters and cankers are the primary preventive steps to ensure Pines are less susceptible to this disease. Regular inspections should be done beginning around May.
Preventive pruning is also advised, by removing the lower branches, regardless of symptoms is known to prevent the appearance and spread of these fungi.
Removing Ribes from the area is often employed, but it might not be effective, as these plants regenerate easily and have great survival abilities that make them hard to eradicate.
Heal
If lower branches are infected, they can be cut off, stopping the spread of this disease. However, if the trunk is infected, there isn’t any solution, and the tree will eventually die. Fungicides can be employed in late summer, and herbicides too, for Ribes control.
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