Broom rust
Melampsorella caryophyllacearum

• Witches' brooms, a clump of small weak branches arising from one point on a larger branch, form in infected trees
• Needles on brooms are pale green to yellow in summer
• Needles die and fall off in autumn, leaving a clump of bare branches in the winter
• Yellow to orange bumps form on needles within the witches' broom, and may release powdery orange fungal spores in summer
• The branch at the base of the broom may be unusually swollen or cracked
• Also infects chickweed, causing orange spots or blotches on leaves
• More information on Broom rust