10 



CIRCULAR NO. 129, BUREAU OF PLANT INDUSTRY. 



also by Pechon * on leaves of diseased trees in the open forest. Re- 

 cently another symptom which is rather common has been noted on 

 trees 5 or more years old. This is the dying of one or more of the 

 lowest lateral bi'anches which are located within the affected area on 

 the stem of the tree. The dead branches are usually abnormally 

 swollen at the base. 



The stunted, compact appearance of the toj) is })y no means a 



constant sym})tom of the disease. In a 

 diseased lot of 10,000 trees 8 years old 

 the AVTiter could detect no difference in 

 growth between a])])arently healthy trees 

 and those which bore fruitmg bodies by 

 the himdred but which aj)])arently bore 

 fruitmg bodies in 1912 for the first time. 

 The stunting usually shows mostly in 

 stock that is 4 and 5 years of age. 



It can not be expected that any one 

 or all of these symptoms will be found 

 in all the trees affected with this disease. 

 The swellmg of the bark is the most 

 constant symptom, but it may be lack- 

 ing, while some othcv sym{)tom is evi- 

 dent enough to show the presence of the 

 disease in a suspected lot of trees. 



There is some danger of confusing the 

 roughened bark caused by the attacks 

 of colonies of the msect Cliermes pinicor- 

 ticis Fitch with the roughenmg caused 

 by the blister rust, 

 difference between 

 roughening. In the 



very UTCgularly cracked and fissured and 

 there is usually some evidence of the 

 insects themselves (figs. 2 and 3). In the 

 latter form (caused by Cronartium rihicola) the bark is usually 

 fissured more deeply and many of the cracks extend horizontally 



There is a decided 

 the two forms of 

 former the bark is 



Fig. 1.— Stem of young, healthy white- 

 pine tree. Note the smooth bark. 



With the former the bark scales are rather thin, 

 latter they are apt to be decidedly thicker and 



(figs. 4 and 5), 

 while with tho 

 heavier. 



Th(Te can be no doubt that this fungus will establish itself here 

 if allowed to do so. The writer has mentioned ^ the discovery of 

 uredospores on llibes leaves iji one case where Ribes was near 



' Pechon, L. Prineipales maladies des arbres et des peuplements forestiers. Bulletin, Soci^t^ 

 Centrale Fore.stiere de Belgique. Ann. 14, libr. fi, p. 329-;«0, 1907. 



2 Spaulding, Pcrley. The blLster rust of while pine. U. S. Department of Airriciiltiire. Bureau of Plant 

 Industry, Bulletin 20G, 88 pp., 5 figs., 2 pis.. Hill. 



I (Mr. 129] 



