PEACH SCAB AND ITS CONTKOL. 31 
usual type, always on/ the lower surfaces. No marked difference was observed in 
the results from inoculations upon the very young and the manure leaves. Sparse 
infection developed upon the leaves of the tree inoculated with the leaf strain of 
the fungus, though none was found upon the twigs. No disease developed upon the 
controls. 
Experiment 5, July 11, 1914. 
Sources of inoculation. — Cladosporium carpophilum: (a) Fruit strain (isolated from 
an overwintered scabbed peach at Madison, Wis., May 11, 1914); (b) twig strain; 
(c) leaf strain; all from 17-day-old cultures. 
Methods. — The experimental trees were potted Chili. One was inoculated by 
spray with the fruit strain and one with the twig strain, while two were similarly 
treated with the leaf strain. Three other plants were inoculated upon marked areas 
with the twig strain, one upon the upper surfaces, one upon the lower surfaces, and 
one upon both surfaces of the leaves. The areas to be inoculated were surrounded 
by circles of india ink, and the sporiferous suspension was applied in small drops 
by means of a camel's-hair brush. The ink was allowed to dry before the inocula- 
tions were made. Two plants were sprayed with sterile distilled water as controls. 
Results. — On the trees inoculated by spray with the fruit, twig, and leaf strains, 
the disease developed typically and abundantly upon the lower surfaces of the leaves 
and rather sparsely upon the twigs. The leaf strain occasioned slightly less infection 
than the others, but materially more than in similar preceding tests. This increase was 
probably due to the fact that special care was taken to have an abundance of spores 
in the suspension used for this inoculation. On September 29 the tree inoculated 
only upon the upper surfaces of the leaves showed no infection. On the tree inocu- 
lated only upon the lower leaf surfaces, 14 of 29 inoculated areas showed infection. 
On the remaining inoculated plant, 66 of 98 inoculated areas on the lower surfaces 
of the leaves showed infection, while no disease was evident upon 93 similarly treated 
areas upon the upper surfaces. No infection was observed except on inoculated 
areas. The control plant developed no evidence of infection. 
REISOLATION OF THE FUNGUS. 
Numerous microscopic examinations showed that Cladosporium 
carpophilum was uniformly associated with the lesions produced by 
inoculation. The fungus was reisolated from twig and leaf infections 
induced by the fruit, twig, and leaf strains, respectively. The 
morphological and cultural characters of the reisolated strains were 
typical of G. carpophilum. 
CONCLUSIONS. 
These experiments show (1) that Cladosporium carpophilum from 
cultures of single-spore strains isolated from scab lesions on (a) 
fruit, (b) twigs, or (c) leaves of the peach is capable of producing 
abundant typical infection upon peach twigs and leaves; (2) that 
natural infection of the leaves occurs chiefly, and apparently exclu- 
sively, upon the lower (dorsal) surfaces; (3) that young or mature 
leaves may be abundantly infected; (4) that the period of incubation 
for leaf infection may vary from 25 to 45 days, and probably more, 
depending upon conditions; (5) that the period of incubation for 
twig infection approximates that for leaf infection; and (6) that 
under favorable conditions secondary twig and leaf infections may 
appear in the latter part of the summer. 
