BUSH FRUIT PRODUCTION 



gooseberry. Pines cannot reinfect pines. That 

 is the weak point in the life cycle of this 

 scourge of the pines, and the only circum- 

 stance that prevents the rapid destruction of 

 all our white pine forests, even as the chestnut 

 was eradicated. 



This disease gains entrance to the pine tree 

 through the needles and small twigs. It grows 

 in the inner bark and spreads until it reaches 

 the trunk and girdles it. Spores are discharged 

 in spring from the rust-colored blisters on the 

 pines. They are light and may drift with the 

 wind for hundreds of miles to infect currant 

 and gooseberry leaves and produce the next 

 stage of the fungus. 



During the summer, blister rust spreads 

 locally from currant to currant or gooseberry, 

 but, beginning in midsummer, another kind of 

 spore is produced which may infect pines. 

 These spores have not been known to produce 

 an infection on pine trees at a distance greater 

 than 900 feet from the currant bush which was 

 the source of infection. By removing cur- 

 rants from the vicinity of pine trees, then, this 

 disease may be controlled. 



Black currants are much more susceptible 

 to this disease than others^ and when infected 

 they produce hundreds of times as many pine- 

 infecting spores as most red or white varieties. 

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