266 JOURNAL OF FORESTRY 



Finally, the only hope for control lies in the fact that the disease 

 to propagate itself requires the intermediary host of Ribes. The part 

 this host plays in propagation of the disease is elucidated, and it is 

 shown that some important points are still undecided, such as the 

 wintering of the rust on currant and gooseberry bushes and the length 

 of time that spores remain viable; but enough experience has been 

 'had to warrant the propriety of preventing shipments of these plants. 



The author then formulates twelve propositions of control as 

 follows : 



1. Exclusion of all foreign white and other five-leaved pines 

 (which has already been done). 



2. Exclusion of all foreign species of the genus Ribes according 

 to Gray's Manual, if known to be carriers of the rust (which has 

 already been done by the United States). 



3. Examination in plantations, hedges, shelter belts, etc., of all 

 white pines originating from any foreign sources. 



4. Destruction in any such plantation, hedge, shelter belt, etc., of 

 each and everj^ tree found infected even in the smallest degree. 



5. Examination of Ribes, wild or cultivated, in the neighborhood 

 where infected pines may be found ; if disease be found, the area 

 should be proclaimed as a danger area. 



6. Systematic lookout, during April, May, and June, for blister 

 rust on native pines ; and from June to October for currant rust, 

 followed by immediate report and proclamation as danger areas, 

 wherever disease be found. 



7. Strict quarantine against the export of white pine or other 

 five-leaved pines from any danger area. 



8. Strict quarantine against the export of currant or gooseberry 

 stock from nurseries in any danger area, until a license has been 

 granted by an authorized government official that neither stage of the 

 rust has occurred on the premises of the licensee, while, at the same 

 time, all pines have been destroyed throughout the danger area. 



9. Destruction of all wild species of Ribes acting as carriers in 

 the neighborhood of valuable standing white pine timber. 



10. Planting of deciduous tree shelter belts surrounding new pine 

 plantations. 



11. Mixed forestation. 



12. Raising of pine seedlings for future supplies from home- 

 grown seed outside of danger areas. 



The Control of the White Pine Blister Rust. Canadian Forestry Journal, January, 

 1917. 



