64 
FLORIDA STATE HORTICULTURAL SOCIETY 
the host plant parts when following each 
other too closely. 
The final proving ground for spray 
materials, to determine which is best 
adapted for a particular purpose, is in the 
grove itself. Comparative tests, checked 
by leaving a small block of unsprayed 
trees, carried on systematically year after 
year, will reveal the strong and weak 
points of the spray materials. It would 
be a distinct advantage to the industry if 
more growers would carefully plan and 
conduct such tests for their own 
guidance, and information regarding ef¬ 
fectiveness of control, cost, and net re¬ 
turns under their own peculiar condi¬ 
tions. 
The whole question of whether spray¬ 
ing is a proper means of control depends 
after all upon the peculiar life habits of 
the parasitic organism and its relation¬ 
ships to its host. Wei cannot discuss 
these in detail at the present time. The 
three citrus diseases with which the 
spraying experiments of our office are 
concerned at the present time are scab, 
melanose and withertip. All three affect 
various parts of the plant besides the 
fruit, but it is towards the protection of 
the latter that we center effort in spray¬ 
ing. 
I will briefly indicate the lines along 
which we are working in our tests: 
Scab infections occur as a rule early 
in the development of the fruit, from the 
blossoming period until the fruit is an 
inch or somewhat more in size. To 
adequately protect during this period of 
about two months, requires three or pos¬ 
sibly four spray applications, the first be¬ 
ing made as soon as enough bloom has 
dropped to expose a fair setting of young 
fruit, the second ten days to two weeks 
later. Even before these, on the early 
spring flush of growth, a clean-up appli¬ 
cation is advantageous in tending to re¬ 
duce the early spread of the disease on 
leaves. 
The first melanose fruit infections usu¬ 
ally occur during the scab danger period, 
and thorough spraying for scab will tend 
to reduce melanose. Under severe con¬ 
ditions one or two additional later appli¬ 
cations will be needed. 
Withertip or anthracnose of grape¬ 
fruit and orange usually affects the fruit 
late in the season. The use of sulphur 
sprays during the summer for insects 
tends to control it. Where this trouble 
is severe a special protective application 
in early fall is advisable. 
The cumulative effects of following a 
sound spraying system throughout the 
year in reducing the sources of infection 
for the following season, must not be 
overlooked. The best results from spray¬ 
ing are usually attained after it has been 
practiced a year or more. 
I wish to emphasize again the impor¬ 
tance of eliminating in so far as practi¬ 
cable hold over sources of infection, es¬ 
pecially through the removal of dead 
limbs and twigs that harbor melanose, 
and withertip organisms. Judicious prun¬ 
ing further adds to the efficiency of spray¬ 
ing by giving a less dense top that allows 
the spray to penetrate better. The admis¬ 
sion of light and air to the interior of 
the tree tends to eliminate moisture con¬ 
ditions that would prove favorable for 
fungus infection. 
In conclusion I wish to utter a word of 
