248 EXPERIMENT STATION EECOED. 



Apple varieties show a very wide range of susceptibility, and even different 

 trees of the same kind show variation. Lists are given of varieties found to 

 be immune, resistant, or more or less susceptible. 



Treatment of apple canker diseases, J. C. Whitten (Missouri St a. Bui. 131 

 (1915), p. 4S3). — ^The indications are that whitewashing the trunk of apple 

 trees protects them from the entrance of canker by preventing the undue rise 

 of temperature and resulting scald on the sunny side of the tree. 



Canker can be eradicated if treatment is commenced before' it has gone so 

 deep as to weaken the wood of the tree. 



A nursery disease of the peach, M. T. Cook and C. A. Schwabze (Ahs. in 

 Phytopathology, 4 (1914), No. 6, p. 394). — The authors' attention was called to 

 a peculiar disease of Elberta peaches in the nursery in 1914. 



The disease is said to attack the young shoots a few inches back of the tips, 

 producing cankers on one side and causing a characteristic curving as a result 

 of the growth on the uninjured side. The cankers originate as small brown 

 spots and gradually enlarge until they are 2 or 3 cm. in length. The diseased 

 area becomes brown and depressed, and finally splits down the center. Gum 

 exudes from the split. The causal organism is considered a species of Sphse- 

 ropsis and successful inoculation experiments have been carried on with it. 

 So far as the authors' observations go, the trouble is of rather limited dis- 

 tribution, 



A wilt disease of Japanese and hybrid plums, B. B. Higgins (Ahs. in Phyto- 

 pathology, 4 (1914), No. 6, pp. 398. 399). — For a number of years a destructive 

 disease, locally known as plum wilt, has been reported to the Georgia Experi- 

 ment Station, and investigations have been conducted regarding its cause. 



According to the author the disease is caused by a fungus which enters 

 through wounds, the hyphse passing rather slowly toward the center of the' 

 tree, as well as up and down through the water ducts, causing the formation of 

 gum which plugs the water ducts and cuts off the water supply. The leaves 

 wilt suddenly and then dry up. Apparently about a year is consumed from 

 the infection to the death of the tree. The fungus has been isolated, grown in 

 cultui'es, and its parasitism demonstrated by means of inoculation, but the 

 identity of the organism has not been determined. 



Studies on Plasmopara viticola, C. T. Gregory (Ahs. in Phytopathology, 4 

 (1914), No. 6, p. 399). — In a study of the downy mildew of the grape the author 

 found that infection could take place only through stomata, never through 

 injuries. Experiments have demonstrated that conidia sown on the upper 

 surface of the leaf could cause infection provided a continuous film of water 

 extends over the margin to the lower surface. The discoloration of the lesions 

 is considered due to decomposition of the chlorophyll and chloroplastids. The 

 swelling of the 'stem of the host is said to result from the hypertrophy of the 

 cells and the intussusception of mycelium between the cells. 



The conidiophores are usually said to be produced through stomata, though 

 they may burst through the loose tissue above the veins or directly through the 

 epidermis of the flower pedicel. The inability of the fungus to fruit on older 

 berries is considered due to the absence of stomata. 



Citrus canker, A. B. Massey (Ahs. in Phytopathology, 4 (1914), No. 6, p. 

 397).— This is a brief note on the occurrence of citrus canker in south Alabama 

 and elsewhere, a previous account of which has been given (E. S. R.. 32, p. 53). 



A new rust of economic importance on the cultivated snapdragon, G. L. 

 Peltier and C. C. Rees (Ahs. in Phytopathology, 4 (1914), No. 6, p. 400). — 

 According to the authors the snapdragon is becoming of some importance as a 

 greenhouse crop. Recently the culture has been interfered with by a new rust. 



