Figure 1 . --Symptoms of limb 

 rust infection in mid- crown 

 typically include a zone of 

 dead, leafless branches. 

 Above and below this zone 

 are recently killed branch- 

 es that retain discolored 

 needles and then branches 

 that are still living. 



No intensive outbreaks of limb rust have been found in species other than ponderosa and Jeffrey pines. 

 The west coast form (var. ponderosa) of ponderosa is seldom attacked, but the Rocky Mountain form (var. 

 scopulorum ) suffers more from limb rust than any other pine. 



CAUSAL FUNGI 



Several related rust fungi cause limb rust. All of them are in or are apparently derived from the 

 species group called Cronartium coleosporioides. Two distinctly different forms of this group, 

 Peridermium stalactiforme and Peridermium filamentosum, are associated with limb rust on pine. 



P. stalactiforme causes limb rust of Jeffrey pines in California and western Nevada. Its alternate 

 hosts are Indian paintbrushes (Castilleja) and related plants. Infection of pine results only from spores 

 that are produced on these alternate hosts. P. stalactiforme causes cankers rather than limb rust on most 

 pine species that it infects; hence "limb rust" designates a kind of disease or symptom, not a distinct group 

 of fungi. 



P. filamentosum consists of at least three races in the United States and probably others in Mexico. 

 One race alternates to Indian paintbrushes , thereby resembling P. stalactiforme in life cycle (but not in 

 appearance). It is common in the Rocky Mountains and the Southwest. Alternate hosts are unknown 

 for the other two races. One of them attacks ponderosa pine in Utah and adjacent States; the other is on 

 Jeffrey pine throughout most of that tree's distribution. Spores of these races are believed to carry 

 infection directly from pine to pine . 



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