NATUKAL CONTROL OF WHITE FLIES IN FLORIDA. 69 
THE DISADVANTAGES ACCRUING TO CITRUS TREES THROUGH THE 
USE OF PARASITIC FUNGI. 
DIRECT INJURY TO FOLIAGE. 
Dr. H. J. Webber gave the subject of direct injury to foliage 
some consideration in connection with the brown fungus and reported 
as follows : 1 
Old leaves on which the larvae have been dead for some time, and on which the 
fungus has been exposed for an extended period to the action of rain, etc., clearly 
show the slight damage to the leaf caused by this fungus. Leaves which were observed 
in March, 1896, to be badly infested with the fungus were found in December of the 
same year to show only the remains of the pustules, the hypothallus having been 
entirely washed away. That the fungus does some damage to the tree can not be 
denied, but this is clearly a secondary effect. 
The secondary injury referred to by Dr. Webber has been noted 
by the authors. It may be considered as of slight importance. A 
more serious secondary injury frequently results from the prevalence 
of the yellow Aschersonia. Dr. Webber has noted 2 that sooty 
mold frequently surrounds and covers insects infested by the red 
Aschersonia. He states: 
The honeydew collected around the infected insects furnishes nourishment for 
the sooty mold, which frequently springs up and makes a conspicuous growth. The 
growth of the sooty mold is more rapid than that of Aschersonia so that it some- 
times happens that a rank growth of the sooty mold smothers both the insect and the 
Aschersonia. 
The condition described is one which unquestionably interferes 
seriously with the respiratory functions of the infected leaf. The 
extent of the injury has never been estimated, so far as known to 
the writers. Fortunately this condition is not the usual one where 
the infection consists of the red Aschersonia. Such a condition is, 
however, quite typical when the yellow Aschersonia is abundant. 
Moreover, the yellow pustules themselves, being much larger than 
the red pustules developing on the citrus white fly, cover a corre- 
spondingly larger leaf surface. As has been indicated the secondary 
injury resulting from the yellow Aschersonia infection is of some 
importance and without doubt partly offsets the benefits resulting 
from the destruction of the white-fly larvae and pupa?. 
INDIRECT INJURY THROUGH THE DISUSE OF FUNGICIDES NEEDED TO COMBAT FUNGOUS 
DISEASES. 
In Florida the control of diseases 3 of citrus by means of fungicides 
is seriously interfered with by the disadvantages and supposed 
disadvantages of the destruction of fungous parasites of destructive 
i Bui. 13, Div. Veg. Phys. and Path., U. S. Dept. Agr., p. 29, 1S97. 
2 Ibid., p. 23. 
3 The principal diseases preventable or partly controllable by means of applications of fungicides are 
known as melanose, die back, anthracnose, scab or verrucosis, withertip, and scaly bark. For the treat- 
ment of these diseases publications of the Bureau of Plant Industry of this department and of the 
Florida Agricultural Experiment Station should be consulted. 
