. Fig. 22.—Gall rust on digger pine. cies of Bibes (see "Currant and Gooseberry, Native," p. 19). The disease cannot pass directly from pine to pine but must first infect Bibes from pines and there produce spores to infect other pine trees. The fungus may spread from pine to Bibes over distances as great as 150 miles, but from Bibes to pine the maximum infection range is only about 300 yards under normal conditions. In new localities, therefore, blister rust is usually found first on currant or gooseberry bushes. After pines are first in- fected, a period of two to three years elapse
. Fig. 22.—Gall rust on digger pine. cies of Bibes (see "Currant and Gooseberry, Native," p. 19). The disease cannot pass directly from pine to pine but must first infect Bibes from pines and there produce spores to infect other pine trees. The fungus may spread from pine to Bibes over distances as great as 150 miles, but from Bibes to pine the maximum infection range is only about 300 yards under normal conditions. In new localities, therefore, blister rust is usually found first on currant or gooseberry bushes. After pines are first in- fected, a period of two to three years elapses before a new crop of spores is produced. Federal and state authorities are carrying on an extensive campaign to limit the spread of this disease and prevent serious damage to valuable stands of sugar-pine and western-white-pine timber. This is done mainly by eradicating susceptible species of Bibes, since the fungus cannot go from pine to pine. Any suspicious symptoms on either host should be
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