582 EXPERIMENT STATION KECORD. 



the apples could come from these canker spots on the branches, and it is probable 

 that except in a few cases the first or early infection comes solely from these canker 

 spots and not from the mummy fruit. The appearance of the bitter rot canker is 

 described at some length and preventive measures are suggested. During the winter 

 time the mummy fruits and cankers should be removed, or the fungus could probably 

 be destroyed by spraying the trees with a solution of cojjper sulphate. The disease 

 can be kept in check during the summer by repeated applications of Bordeaux 

 mixture. 



Pear blight in California, N. B. Pierce {Scienee, v.. ser.,16 {1902), No. 396, j^p. 

 193, 194). — Pear-leaf bliglit, although doubtfully reported in California for many years, 

 was observed in a typical form in southern California in 1899. The disease assumed 

 its normal epidemic form and spread over several counties in a short time, occasioning 

 great damage. In the spring of 1900 it had developed seriously in a number of 

 widely separated regions, and is reported as occurring to a considerable extent in the 

 leading pear growing districts of southern California, and of the San Joaquin and 

 Sacramento valleys. It has hitherto been believed that the atmospheric conditions 

 in the hot interior valleys of California would be detrimental to the destructive 

 development of pear ])light, but the facts presented are quite to the contrary. 



In California there are said to be 2 distinct forms of the disease, a spring and 

 summer form, likewise a winter epidemic, the latter form being by far the more 

 destructive. The winter form of disease, which by inoculation experiments has been 

 proved identical with the spring form, has some distinguishing characteristics. It sel- 

 dom or never attacks the tree at points higher than a man's head, always affecting the 

 trunk or base of the main limbs, and the infection takes place about the time the 

 crop is gathered or shortly after, continuing active and destructive during the months 

 of November, Deceml)er, and January. It may also occur in orchards which have 

 shown little or no signs of the spring form of the disease. 



The infection usually occurs in the short spurs develope<l upon the base of the 

 main limbs or on the trunk of the trees. These spurs not infrequently develop clus- 

 ters of flowers late in the fall, and seldom occur more than 5 or 6 ft. from the ground. 

 The winter temperature is sufficiently warm to permit the blight bacillus to grow, 

 and as the affected parts can not be removed by pruning without detriment to the 

 tree, the winter development has resulted in more serious injury and greater losses 

 of trees than the spring form of the disease in the East. In the winter blight, as 

 well as the spring form, the growing tips of purely vegetative shoots occasionally 

 serve as points of infection. This has been shown possible by the visit of bees which 

 are attracted to the buds for the deposit of glue or wax which occurs on the winter 

 buds. The agency of bees in distrilniting the pear blight is shown by statements 

 regarding the serious affection of a number of orchards near large colonies of bees. 



Notes on canker and black rot, P. J. O'Gara {Science, n. ser., 16 {1902), No. 

 402, pp. 4-^4, 435). — During the summer of 1901 several specimens of sumac {Rhus 

 (jhOim), occurring on the campus of the University of Nebraska, were found affected 

 with the canker caused by Sphnropm rhoina. During the summer of 1902 experi- 

 ments were carried on to determine whether this fungus and the S. malorum occur- 

 ring on the apple may not be the same. Pure cultures of each were made and their 

 behavior was identical in every particular. Sound apples inoculated with spores, on 

 the fourteenth day after inoculation, were blackened and densely dotted with the 

 protruding pycnidia. Spores obtained from the inoculated apples were used to inoc- 

 ulate healthy branches of both the apple and sumac, and so far no differences can be 

 observed in the growth of the different species. The experiment seems to establish 

 that <S'. rhoina will cause the black rot on the fruit of the apple, and will also produce 

 the typical canker on the branches and limbs just as readily as S. malorum. Although 

 the evidence is not yet complete, it is believed that the 2 species are identical. 



The gray rot of grapes, R. Roger {Jour. Agr. Prat., n. ser., 4 {1902), No. 39, 



