1917] DISEASES OF PLANTS. 451 



mixed with the infested soil. All forms of the nematode are said to be destroyed 

 by short exposure to dry heat, the seed not being injured when exposed for ten 

 minutes to temperatm-es of 149 to 158° F. This is suggested as a method for 

 the control of the nematode if it should be established that it is introduced 

 through the seed. 



Rhizoctonia and Sclerotium. rolfsii on sweet potatoes, L. L. Habteb (Phyto- 

 pathology, 6 {1916), No. 3, pp. 305, 306). — The author reports the pre-ence of 

 Rhizoctonia on sweet potatoes, particularly in seed beds which have been 

 too frequently watered, and of S. rolfsii on similar plants. The latter fungus 

 is said to be quite destructive in Florida and Texas, sometimes completely 

 destroying all plants in a hotbed. 



A specific mosaic disease in Nicotiana viscosum distinct from the m.osaic 

 disease of tobacco, H. A. Aixabd (U. S. Dept. Agr., Jour. Agr. Research, 7 

 {1916), No. 11, pp. 481-^6, pis. 2). — The author reports having observed in the 

 trial grounds at Arlington, Va., three plants of N. viscosum and a hybrid plant 

 between that si)ecies and N. tabacum showing unmistakable symptoms of mosaic 

 disease. This disease in its symptoms seems identical with the mosaic disease 

 of tobacco, but the virus behaves very differently from that of tobacco mosaic 

 disease in all inoculation tests. The author is of the opinion that this is a 

 distinctive type of mosaic disease affecting A^. viscosum and that in some 

 manner it has originated from the ordinary form of mosaic disease. 



During the same season, the author's attention was called to the typical 

 symptoms of mosaic disease in peppers, which gradually spread over the whole 

 field. Tomato plants in adjoining rows, however, were unaffected, and the ex- 

 pressed sap of the most severely affected pepper plants failed to produce the 

 mosaic disease in young tobacco plants. Whether this disease was infectious to 

 healthy pepper plants or was in some way related to the mosaic disease affect- 

 ing N. viscosum was not determined. 



Tomato blight, D. H. Jones {Ann. Rpt. Ontario Veg. Growers' Assoc, 11 

 {1915), pp. 60-61, figs. 2). — An account is given of a disease of tomato which 

 may cause heavy losses from plants grown under glass, but which has been 

 found to only a very limited extent in the field. The trouble resembles in many 

 respects the brown rot of solanaceous plants, but it has not been connected with 

 attack by fungi, bacteria, or insects. It is thought to be due to some soil 

 factor, possibly an injurious chemical reaction affecting the plant through the 

 root system. Good results have been obtained in a limited number of cases 

 from treating the soil with steam. 



Phytophthora infestans on tomatoes, F. D. Kebn and C. R. Okton {Phyto- 

 pathology, 6 {1916), No. 3, pp. 284-287, figs. 2). — A report is given of an unusual 

 outbreak of P. infestans on tomatoes in Pennsylvania in 1915. The fungus 

 appears to attack leaves, stems, and fruit with about equal virulence, and there 

 is believed to be some connection between weather conditions and the outbreak 

 of the disease. 



Phomopsis mali on young apple and pear trees in California, Elizabeth 

 H. Smith {Abs. in Phytopathology, 6 {1916), No. 3, p. S09 ) .—Attention is called 

 to a disease of young apple and pear trees described by Roberts as due to 

 P. mali (E. S. R., 28, p. 747). The trouble seems to be confined to one to three 

 year old trees and is said to have been thus far of no great economic im- 

 portance. 



Observations on sour sap disease of apricots, Edith H. Phillips {Abs. in 

 Phytopathology, 6 {1916), No. 3, p. 309). — Apricot trees are said to be affected 

 with sour sap, or black heart, the first indication of the trouble being observed 

 in the outer branches, which begin to die back, and in the wood in which brown 



