DANGEROUS INTERNATIONAL FOREST TREE DISEASES 103 



P. taeda L. 

 P. virginiana Mill. 

 Introduced to North America : 

 Pinus canariensis C. Sm. 

 P. densifl-ora Sieb. & Zucc. 

 P. halepensis Mill. 

 P. mugo Turra (as P. montana Mill.) 

 P. nigra Arnold var. poiretiana (Ant.) 



Aschers. & Graebn. (as P. pinea Habl.) 

 P. sylvestris L. 

 P. thunbergii Pari. 

 Scrophulariaceae — Castitteja angustifolia Nutt. var., C. linariae- 

 folia Benth., and C. miniata Dougl. have been infected artificially 

 with western gall rust ; in addition, species of Melampyrum* 

 Orthocarpus. Pedicul-aris. and Rhinanthus have been suggested as 

 possible suscepts. 

 Literature: 

 Arthur, J. C. Manual of the rusts in United States and Canada. 



Purdue Res. Found., Lafayette, Ind., U.S.A. 1934. 

 Meinecke, E. P. Experiments with repeating pine rusts. Phyto- 

 pathology 19 : 327-342. 1929. 

 Peterson, R. S. Western gall rust on hard pines. U.S. Dept. Agr. 

 Forest Serv., Forest Pest Leaflet 50. 1960. 



Stalactiform Rust 



W. G. ZlLLER 



Forest Entomology and Pathology Branch* Canada Department of 

 Forestry, Victoria, British Columbia 



Perid-ermium stalactiform^ Arthur & Kern, stalactiform rust, causes 

 branch and trunk cankers of hard (2- and 3-needle) pines in North 

 America. Trees of all ages, especially young trees, are susceptible. 



In spring, droplets of clear, viscid exudate emerge from the pycnia 

 on the living bark of the cankers, soon followed by conspicuous, pale- 

 yellow blisters, the aecia of stalactiform rust. A few days later the 

 aecia rupture, releasing clouds of orange-yellow aeciospores. The 

 aeciospores infect alternate hosts (Scrophulariaceae, listed below) on 

 the foliage of which uredinio-, telio-, and basidiospores are produced 

 3, 5, and 7 weeks after infection, respectively. The basidiospores 

 are short-lived and cannot withstand extremes of temperature and 

 moisture. Under suitable environment the basidiospores may infect 

 susceptible pines growing nearby. The time between infection of 

 pine, in late summer, and the appearance of the first crop of aeciospores 

 on the young branches may vary from 10 months to 4 years de- 

 pending on the age of the pines infected, climate, and other factors. 

 There is no evidence that stalactiform rust spreads from pine to pine 

 directly like western gall rust; host alternation appears to be obligate. 



Peridermium stalactiform^ may be recognized from the following 

 characteristics : 



Pycnia and aecia on the rcnighened bark of elongate branch and 

 trunk cankers that reach a length of 30 feet or more but do not 



