453 



BLISTER RUST ON WHITE PINE 



J. F. MARTIN, PERLEY SPAULDING 



White pine blister rust is a fungus 

 that attacks and destroys the highly 

 valued white, or five-needled, pines. It 

 spreads to pines from its alternate 

 hosts, currants and gooseberries, with- 

 out which the fungus cannot infect 

 white pines. Thus the disease is con- 

 trolled by removing the alternate host 

 plants, commonly called ribes, in the 

 vicinity of white pines. 



A point to note is that white pine 

 blister rust is an introduced disease, not 

 a native. Most native tree diseases are 

 curbed by natural conditions, so that 

 in a given outbreak they are fatal only 

 to individuals or groups of individuals. 

 But introduced diseases are free from 

 the natural controls of their native hab- 

 itat; in their new environment, if the 

 conditions are unusually favorable, they 

 sometimes become epidemic and de- 

 structive, although the existence of an 

 entire tree species is rarely endangered. 



White pine blister rust was first 

 found in North America at Geneva, 

 N. Y., in 1906. It occurred on culti- 

 vated ribes, and the bushes were 

 promptly destroyed. The disease was 

 found again in 1909 in new plantations 

 of eastern white pines, large numbers of 

 which had just been imported from 

 Europe to fill a heavy demand for for- 

 est planting stock. The shipments went 

 to most of the Northeastern and Lake 

 States, and to eastern Canada. Many 

 of them contained infected trees, and so 

 the disease was widely distributed 

 within the native range of eastern white 

 pine. The State officials concerned im- 

 mediately agreed on concerted action 

 to find and destroy all infected pines 

 and remove all ribes within 500 feet of 

 the diseased plantations. They hoped 

 thus to eradicate the fungus. The ac- 

 tion delayed the spread of the disease, 

 but in 1913 it became evident that in- 

 fection had spread to the native white 

 pines. By 1915 all hope of eradicating 

 the fungus from North America was 



abandoned. Efforts then were concen- 

 trated on local control to prevent seri- 

 ous damage in stands of eastern white 

 pine. 



In 1921 the disease was found near 

 Vancouver and in northwestern Wash- 

 ington on western white pine. The ori- 

 gin of that outbreak was a shipment of 

 white pine nursery stock made directly 

 from France to Vancouver in 1910. 



Out of experiences with white pine 

 blister rust, chestnut blight, and some 

 forest insects that were known to have 

 been imported from abroad came the 

 enactment in 1912 of a Federal Plant 

 Quarantine Act. The first quarantine 

 under it prohibited further importa- 

 tion of white pines. Later the interstate 

 movement of white pines and ribes was 

 regulated to prevent spread of the dis- 

 ease by shipment of infected host 

 plants. The affected States also enacted 

 laws to control the blister rust or pro- 

 mulgated quarantines and regulations 

 under established pest control laws per- 

 taining to control of blister rust. Such 

 action has been taken by 32 States. 

 In 1917 a Federal embargo was placed 

 on the movement of white pines and 

 ribes from the Eastern States to points 

 west of the Great Plains to prevent 

 westward extension of the disease 

 through the shipment of infected host 

 plants. This embargo was lifted in 1926 

 after it became evident the disease had 

 become widely scattered in western 

 white pine forests. Adjustments were 

 made in the Federal white pine blister 

 rust quarantine from time to time to 

 take care of problems created by the 

 natural spread of the rust into unin- 

 fected territory and the removal of 

 ribes in control areas. 



White pines are among our most 

 valuable and desirable forest trees. 



Of the eight native species, three 

 are among our leading timber species. 

 They are the eastern white pine, which 

 grows from Georgia to Maine and west 



