DISEASES OF PLANTS. 247 



The control of potato diseases, H. T. Gussow {Ann. Rpt. Quebec Soc. Protec. 

 Plants [etc.], 7 (19U-15), pp. 43-49, fig. 1).—A. discussion is given of potato 

 canker, which is said not to be known to exist at present in Canada, and of 

 powdery scab, which has not been observed west of Quebec, for protection from 

 wliich directions ai-e given, applying to infected tubers or soil, to diseased or 

 insect-infested plants, or stored tubers. 



Distribution of the virus of the mosaic disease in capsules, filaments, 

 anthers, and pistils of affected tobacco plants, H. A, Allaed ( U. S. Dept. Agr., 

 Joxir. Agr. Research, 5 (1915), Ko. 6, pp. 251-256, pi. 1). — Continuing earlier 

 woi'k (E. S. R., 30, p. 450), the results are given of inoculation experiments in 

 which various parts of the floral organs of plants infected with the mosaic 

 disease were used in an attempt to determine whether the disease might be 

 carried by seeds. 



Successful inoculations were made where filaments, anthers, and pistils fur- 

 nished the inoculating material, and it is believed possible that embryonic de- 

 velopment never proceeds in those ovules actually invaded and infected by the 

 virus of the disease. In all experimental tests, germinable seeds from plants 

 infected with the disease always produced normal, healthy seedlings. 



Fungus and other diseases of the apple and pear, G. P. Daknell-Smith and 

 E. MACKINNON (Dept. Agr. N. S. Wales, Farmers' Bui. 99 (1915), pp. 45, figs. 

 36). — A summary is given of local disorders of apple and pear. 



Canker, here including diseases characterized by extended and persistent 

 lesions of the bark, is produced by Sphwropsis malorum, Glceosporium fructige- 

 num (Glomerella cingnlata), Vnlsa sp., and Phyllosticta sp., while some canker 

 producing organisms not yet recorded here are Nectria ditissima, Nummularia 

 discrefa, Phomopsis mali, and Bacillus amylovorus. Bitter rot (O. fructigenum, 

 ascigerous stage O. cingulata) of apple is controlled with Bordeaux mixture. 

 Black rot (S. malorum or Diplodia sp.) is discussed in connection with varietal 

 susceptibility of apples. Cytospora, the common pycnidlal stage of Valsa, is 

 described. Apple blotch (Phyllosticta solitaria), here very similar to P. pruni- 

 cola, is controlled by Bordeaux mixture. Blight (B. amylovorus) has been kept 

 out of Australia. Mildew (Podosphcera tridactyla or P. oxyacanthce) is con- 

 trolled with a spray of lime sulphur or of iron sulphid, applied when the biids 

 are unfolding. Crown gall (Bacterium tumefaciens) is controlled by rigid re- 

 jection of suspected nursery stock. Apple scab (Ventu7-ia in<equalis, conidial 

 stage Fusicladium dendriticum) is in a degree resisted by about one-third of the 

 varieties named, while pear scab (V. pyrina) attacks severely several varieties. 

 Bitter pit is dealt with at some length in connection with recent statements by 

 McAlpine (E. S. R., 33, p. 582). Glassiness or water core is also described. 



Of noncryptogamic disorders, spray injury, frost band, and chlorosis are 

 briefly discussed. 



Collar blight and related forms of fire blight, C. R. Oeton and J. F. Adams 

 (Pennsylvania Sta. Bui. 136 (1915), pp. 3-23, figs. 14).— A description is given 

 of a form of fire blight which principally attacks the trunks of apple trees 

 near the surface of the ground. This trouble seems to be quite common and 

 destructive in Pennsylvania, and is said to be quite distinct from the winter in- 

 jury and some forms of root rot with which it is often confused. 



The cause of collar blight is Bacillus amylovorus, the well-known fire blight 

 organism, and different varieties of apple seem to vary in regard to sus- 

 ceptibility to attack. 



Among the predisposing factors to collar blight are fertilization, mulching, 

 cultivation, root grafting, and the age of trees. It seems to be more prevalent on 

 trees which have been highly fertilized with nitrogenous manures. INIulching 

 about the trees also is conducive to the appearance of collar blight, and cultiva- 



