352 EXPEEIMEXT STATION RECORD. [Vol. 41 



comparison of tliese two fungi has been noted from anotlier source (E. S. R., 

 39, p. 858). 



Investigation [of white pine blister rust] in the Canadian Department of 

 Agriculture, W. A. McCubbin {Ama: Plant Pest Committee Bui, 2 [1919], pp. 

 13, 14). — Studies carried out in 1917 and 1918 show that uredospores and 

 seciospores of the white pine blister rust fall through the air very slowly, 

 so that their wide disiiersal by air currents is possible. The fact that the 

 effect of sunlight in inhibiting artificial inoculation is to be counted on only 

 during the day decreases considerably the importance of this agency. 



A survey of pine infection areas, made in order to ascertain the actual 

 damage done by this disease, shows an average of 2.3 per cent infected, though 

 the infection percentage recorded ranged as high as 33.54 per cent in one 

 instance. Supposedly about 1 per cent of the pines have suffered new attaclj; 

 each year on the areas examined. 



Apparently the principal factors to be reckoned with as regards pine infec- 

 tion include nearness and number of cultivated Ribes (particularly black 

 currants) and the humidity of the area infested. 



Artificial infection of Kibes species and white pine with Cronartium ribi- 

 cola, G. P. Clinton (Aiiier. Plant Pest Committee Bui. 2 [1910], pp. IJ,, 15).— 

 A study has been made of the degree of infection produced on different species 

 of Ribes grown in crocks. It was possible to trace the germ tubes of both 

 the secial and uredinial spores through the stomata into the leaf tissues, show- 

 ing that the epidermis is probably not pierced in case of ordinary infection. 

 Of 35 species of Ribes tested, 25 species were infected; with secial spores, 24 

 plants out of 36 tests ; and with uredinial spores, 40 out of 59. 



Studies carried out during the fall of 1916 and 1917 on the infection of pines 

 one to three years old by the telial stage gave as the first visible signs of 

 infection the characteristic golden-yellow spots on the leaves, these being noted 

 from 25 days to 6 months after the telia with sporidia were placed on the 

 leaves. Microscopic sections show these golden-yellow spots to be filled with a 

 sclerotial mass of mycelium more or less closely surrounding the fibro-vascular 

 system. Strands of mycelium later run lengthwise near tlie bundles down 

 the leaf into the stem, but cause no discoloration of the leaf. Inoculations 

 of the young stems and unopened buds have not been successful. Within 6 

 months after infection the plants have oozed out pycnial spores, but no plants 

 have yet matured the fecial stage. However, the plants thus far employed, 

 being young, have mostly been killed by the fungus within one or tw^o years 

 after infection. 



Summary of the white pine blister rust situation, H. Metcalf {Amer. Plant 

 Pest Committee Bill. 2 [1919], p. 16). — The results of wi)rk done to date are 

 said to have shown that, even under unfavorable conditions, wild Ribes can be 

 eradicated at a cost which is inconsiderable in comparison with the damage 

 caused by the presence of this host of the white pine blister rust. It is, 

 therefore, practical to plant white pine in the East if the areas are kept free 

 from Ribes to a distance of one-third of a mile of the nearest pine. More and 

 more stress must be laid on local control of Ribes, which has been shown to 

 carry this disease througli the winter. 



Progress of experiments for destroying Bibes with chemicals, \V. S. Regan 

 (Amer. Plant Pest Committee Bui 2 [1919], pp. 15, iO').— Tests begun in 1917 

 .show that in certain cases the chemical method possesses distinct advantages 

 over hand pulling as a means of destroying Ribes. Undiluted fuel oil applied 

 as a fine spray offers a most satisfactory means of this kind, a single thorough 

 application producing defoliation, and under favorable conditions penetrating 

 the bark and killing the plants. Direct sunlight favors and hastens this result, 



