APPLE LEAF-SPOT CAUSED BY SPHAEROPSIS MALOKUM. 51 



On June 3, 1907, purple specks were appearing on the leaves which 

 had been inoculated with Sphaeropsis, and on June 18 these leaves 

 were badly affected with leaf-spot. (PL III, fig. 2.) On a twig 

 bearing 30 leaves, 12 showed a dozen or more well-developed spots, 

 and a few of these leaves had from 80 to 90 spots each. Twelve other 

 leaves on the same branch had from 2 to 10 spots each, while only 

 6 remained free from the disease. On another branch 12 out of 20 

 leaves were badly affected. 



With the exception of an occasional spot, evidently resulting from 

 natural infection, the leaves sprayed with spores of the other fungi, 

 as well as those sprayed with sterile water as a check, remained free 

 from the disease. 



Another experiment was made on June 19, 190T. Spores of Sphae- 

 ropsis malorum, G oniothyrium pirina, Coryneum, and Alternaria were 

 used. The work was done at sunset following a shower, so that the 

 leaves were wet. Again the leaves inoculated with the spores of 

 Sphaeropsis malorum soon became badly affected with the character- 

 istic leaf-spot disease, while the others, including the checks, devel- 

 oped no more than an occasional spot. 



Another test was made with Sphaeropsis alone. The young leaves 

 of a 2-year-old tree were inoculated during a period of dry weather 

 in mid- June. The spores were sprayed on the leaves at about 10 

 o'clock, while the sun was shining brightly. At the same time 

 sterile water was sprayed on the leaves of an adjacent tree as a check. 



Though no rain fell for at least six days after the spraying was 

 done, numerous purple specks began to appear on the inoculated 

 leaves within a week and soon developed into the characteristic brown 

 spots. A few spots, never more than one to a leaf, appeared on the 

 checks. The mature spores of Sphaeropsis germinate so rapidly that 

 in dry weather the dews provide sufficient moisture for leaf infec- 

 tion, as indicated by this experiment. 



Inoculations made on June 26, 1907, with Sphaeropsis malorum, 

 Coryneum, and Alternaria gave results similar to those previously 

 recorded for these fungi. From 20 to 50 spots developed on each of 

 the leaves inoculated , with Sphaeropsis, while only a few scattered 

 spots occurred on the leaves of the check and on those sprayed with 

 spores of the other fungi. 



On August 4, 1907, inoculations with Coniothyrium were again 

 tried. Leaves on rapidly growing 2-year-old Ben Davis trees in a 

 nursery were used. The spores were obtained from a fresh culture 

 and were so numerous that they clouded the liquid. The work was 

 done during a light shower and some rain fell the next day. 



The same experiment was repeated on the evening of August 14, 

 1907. Though it did not rain at this time the trees were wet down 

 with sterile water on the following night. 

 12X— v 



