8 BULLETIN 534, U. S. DEPARTMENT OF AGRICULTURE. 
the first spraying for the prevention of blotch infections should be 
well under way when three weeks have elapsed after petal fall. This 
is particularly true during a season of belated blooming due to cold 
or otherwise unseasonable weather, as the period of growth and ma- 
turity of the fungus and its spores does not seem to be influenced so — 
much by such conditions as does the blooming period of the host. 
As determined by artificial inoculations, Phyllosticta solitaria grows 
very slowly and is not perceptible on the fruit until three to six 
weeks after infection has taken place. Ordinarily the blotched areas 
are not large enough to appear conspicuous before the early part of 
July. 
CULTURAL RELATIONS. 
Phyllosticta solitaria will grow on a wide range of culture media. 
Tt will also produce pycnidia on all of the ordinary solid culture 
media. These pycnidia, however, do not produce spores. The only 
medium on which the writer has been able to grow the fungus with 
the formation of both pycnidia and spores is sterile apple wood, 
which was the medium used by Scott and Rorer. Even on this me- 
dium two to three months elapsed in the case of all the strains used 
by the writer before mature spores were produced. 
WEATHER CONDITIONS. 
In orchards in which twig cankers are abundant, dry weather does 
not appear to reduce greatly the number of infections, because prac- 
tically every apple is affected anyway; but in the average blotch- 
infected orchard of the Ozark section the reduction is very notice- 
able. In 1914 the absence of rain during the latter half of May and 
during the first three weeks of June greatly reduced the number of 
infections. In Arkansas the period of heaviest infection did not 
occur until about July 1. In Kansas, where blotch is a particularly 
serious disease, it was found, as Lewis had noted previously in dry 
seasons. that the disease was not greatly hindered by the dry weather. 
The sources of infection, that is, twig cankers, are much more abun- 
dant in Kansas than in Arkansas, and even if a large proportion of 
the expelled spores failed to germinate there would still be enough 
to infect the fruit heavily. Undoubtedly, as in the case of most 
fungous diseases, moist weather is particularly favorable for the oc- 
currence of the maximum number of blotch infections. 
The writer has never been able to note any relation between the 
amount of infection and the temperature extremes during May and 
June. Neither extreme appears to be particularly favorable or par- 
ticularly unfavorable. 
