34 BULLETIN 1474, U. S. DEPARTMENT OF AGRICULTURE 
mer months than on undusted trees, indicating that the fungicidal 
effects of the dust had largely disappeared before entomogenous fungi 
began operations in quantity. 
Experimental and commercial dusting with the present-day dusts 
over a period of three years has not given satisfactory melanose con- 
trol. This is probably due to insufficient adhesiveness. 
COST OF DUSTING 
An average-sized orange or grapefruit tree. 15 or 20 years old, 
requires approximately 1 pound of dust for each application, and if it 
be assumed that two or three properly timed applications of dust 
might be as effective against melanose as one spray application, then 
a tree will require 2 or 3 pounds of dust. At the prevailing prices of 
copper dusts in wholesale lots during the last three years, the mate- 
rial alone would cost from 20 to 30 cents per tree. The cost of appli- 
cation is onh 7 a small fraction of a cent per tree. 
DUSTING UNSATISFACTORY 
To sum up, dust, either copper or sulphur mixtures, with but a 
few exceptions, have failed to give satisfactory control of melanose 
in Florida. In general the results have been so disappointing that 
this method does not appear worthy of trial on a large scale. The 
cost of application on the tree basis is equal to or greater than that 
of standard sprays of proved efficiency. 
SPRAYING FOR MELANOSE CONTROL 
As early as 1896 Swingle and Webber (21) showed that citrus 
melanose outbreaks could be greatly reduced by applications of cop- 
per sprays, and for the control of this disease they gave a tentative 
spray schedule based on their experimental results. In spite of the 
fact that it had been shown that this disease could be controlled by 
applications of sprays, few if any growers attempted to do so, be- 
cause the injurious effects resulting from an abnormally great increase 
in scale insects following applications of copper sprays were usually 
more damaging to the tree and fruit than the severest outbreak of 
melanose. 
"With the introduction of Bordeaux-oil emulsion spray, spraying 
for the prevention of citrus diseases has been put on a far different 
basis and the former objections to the use of Bordeaux mixture have 
been largely overcome. Considerable spraying is now being done 
for melanose control. 
The spraying experiments reported in this bulletin are extensive, 
and records of numerous spraying tests on a commercial basis are 
also given in order that general conclusions of a dependable nature 
may be correctly reached, particularly from the viewpoint of the 
commercial grower. The disease varies in intensity from one grove 
to another, even from tree to tree, owing to terrain, condition of the 
tree, stage of growth at time of infection periods, and many other 
causes. Such factors become more apparent with an increased ex- 
perience with the disease. Because of this lack of uniformity in 
melanose outbreaks the control results necessarily must vary con- 
siderably, and in deducing conclusions from spraying operations 
