PEACH SCAB AND ITS CONTEOL, 



35 



abundant leaf infection appears late in the season, conidia from 

 leaf lesions are most plentiful in late summer and fall. In the cases 

 observed by the writer, the aggregate sporulation from lesions on the 

 leaf appeared to be much less than that from twig or fruit infections. 



Supporting records. — From August 21, 1913, when leaf lesions were first observed 

 in Georgia, until the end of the season, they bore spores in greater or less abundance. 

 In the inoculation experiments at Madison, Wis., conidia were usually present when 

 the lesions became macroscopic . The amount of sporulation and its period of duration 

 upon the individual lesion appear to vary greatly with conditions. 



VIABILITY AND LONGEVITY OF CONIDIA. 



Hundreds of germination tests conducted during the seasons of 

 1912, 1913, and 1914 showed that freshly produced, normal conidia 

 from fruit, twig, or leaf lesions are capable of germinating in sterile 

 distilled water, rain water, or a large variety of nutrient solutions. 

 The frequent paucity of germination from miscellaneously collected 

 field material indicated, further, that imder unfavorable conditions 

 the viabihty of spores may diminish rather rapidly with age. This, 

 however, seems to be of relatively little practical significance, since 

 fresh conidia may be produced Avith the advent of conditions favor- 

 able for infection. The summarized results of a few typical germina- 

 tion tests are given in Table VI. 



Table YI. — Suvimarized results of typical germination experiments with conidia oj 

 Cladosporium carjwphilum. from field material at Cornelia, Ga., in 1913 and at 

 Madison. Wis., in 1914.^ 



Serial No. 



Date. 



Variety. 



Source of lesion. 



Estimated germi- 

 nation in 3 days 

 (per cent). 



Sterile 



distilled 



water. 



I per cent 

 prune de- 

 coction. 



438 . . 



July 1,1913 

 July 22,1913 

 July 24.1913 

 July 26,1913 

 Aug. 22,1913 

 Apr. 13,1913 

 June 7, 1913 

 June 21,1913 

 July 7, 1913 

 July 27,1913 

 Oct. 7, 1913 

 Oct. 9, 1913 

 Nov. 1,1914 

 Oct. 7, 1913 

 Oct. 9,1913 

 Oct. 23.1913 

 Oct. 9, 1913 



BeUe 



Fruit ... 



50 

 10 

 30 

 20 

 

 80 

 95 

 • 50 

 10 

 30 

 50 

 40 

 95 

 60 

 40 

 60 

 95 



90 



492 



Elberta 



do 



15 



505 



do 



do 





507 



..do 



. .do. 2 



90 



536 



Fox 









275 



Elberta 



BeUe 



Over^wntered twig 

 .. ..do.- 



99 



374 



99 



420 



Elberta 



do. 2 



70 



474 



. ..do 



.do. 2 



10 



494 



do 



do. 2 



30 



.558 



Svmimerour... 

 do 



Cunent year's twig 

 . ..do 



95 



566 



95 



731 



Chili 



do 



99 



660 



Summerour... 

 do 



Leaf lamina 2 



Petiole2 



95 



668 



95 



670 



do 



.do 



60 



725 



do 



Leaf lamina 



99 









1 These germination tests were made in open drops upon clean sterile glass slides in moist chambers and 

 incubated in difluse light in the laboratory. Unless otherwise stated the spores were secured from fresh 

 field material. 



2 Spores secured from material which had been held in moist chamber 2 to 4 days. 



A longevity experiment is briefly reported below. 



Experiment 1. — On April 16, 1915, abundantly sporulating 17-day-old cultures of a 

 twig strain of the fungus on steamed bean pods were removed from the culture tubes 



