191T] DISEASES OF PLANTS. 545 



factors may be concerned in the injury. Sun scald is considered to be a late 

 winter injury, as distinguished from crown rot, which is perhaps an early 

 winter injury. Sun scald is, therefore, not induced by late gi-owth or an 

 unripened condition of the tree in the fall, while crown rot is undoubtedly due 

 to this condition. 



As a result of experiments, the author claims that a practical method of 

 controlling sun scald is to spray or paint the trunks of the trees with white- 

 wash in the fall or early winter. This method is considered more feasible than 

 shading with boards or otherwise. 



Control of pear scab, R. E. Smith {California Sta. Circ. 157 {1916), pp. 4, 

 figs. 5). — Suggestions are given for the control of pear scab, plowing under of 

 the dead leaves and two sprayings with Bordeaux mixture as the buds are 

 unfolding being recommended. As an extra precaution a third spraying, with 

 Bordeaux mixture to which lead arsenate has been added for codling moth 

 control, may be given. 



Peach scab and its control, G. W. Keitt {U. S. Dept. Agr. Bid. 395 {1911), pp. 

 66, pis. 6, figs. 6). — The results of laboratory and field investigations on peach 

 scab, due to Cladosporinm carpopliilum, and its control are given. Peach scab 

 is said to occur in practically every important peach-growing district in the 

 United States east of the Rocky Mountains, and its presence has also been 

 recorded in Canada, Europe. Australia, and South Africa. The characteristics 

 of the disease are given, and the life history of the organism is described. 



Inoculation experiments with single spore strains of the fungus from the 

 fruit of the peach and from twigs and leaves gave typical infections in every 

 case, with the exception of the leaf strain inoculated upon the fruit. Scab 

 infection naturally appears shortly prior to the ripening period of the earlier 

 varieties and may continue throughout the season. Primary infection is said 

 to be produced by conidia from overwintered twig lesions. The fungus over- 

 winters in the mycelial stage on living twigs and no evidence has been found 

 of any other type of overwintering that is of practical importance in the life 

 history of the parasite, although it has been shown that the mycelium may 

 survive the winter on fallen fruit and twigs. The varying resistance of dif- 

 ferent varieties of peaches to scab is pointed out, and as a result of the experi- 

 ments of the author and others, it is claimed that it may be satisfactorily 

 controlled by spraying with self-boiled lime-sulphur or with finely divided 

 wettable sulphur. 



Grape anthracnose in America, C. L. Shear {Off. Rpt. Sess. Internat. Cong. 

 Vit., 1915, pp. 111-111, figs. 4). — The author states that while grape anthracnose 

 due to Sphaceloma ampeUnnm has apparently not been found on wild grape- 

 vines native to this country, it is known to attack varieties derived from our 

 native species. A resemblance noted between the anthracnose fungus of the 

 grape and that of some species of Rubus has suggested the possibility of a close 

 relation or identity of the causal organisms, which is to be investigated. 



The unpleasant features of the iron sulphate and sulphuric acid treatment 

 are said to be obviated by the use of the effective combined lime-sulphur and 

 Bordeaux mixture treatment which has been worked out by Hawkins (B. S. R., 

 28, p. 649). This proved to be successful vvhen used in connection with removal 

 of diseased material. 



Studies on Plasmopara viticola (downy mildew of grapes), C. T. Geegoky 

 {Off. Rpt. Sess. Internat. Cong. Vit, 1915, pp. 126-150, figs. 37).— This is an 

 account of studies by the author and by others on the various phases of develop- 

 ment of P. viticola, including the pathological histology and physiology and 

 circumstances determining resistance or susceptibility to downy mildew. 



