16 BULLETIN 1117, U. S. DEPARTMENT OF AGRICULTURE. 
It is evident, therefore, that so far as mealybugs were concerned 
the trees in this grove were in better condition in the unsprayed areas 
than in the sprayed; in fact, there was 5.5 per cent more injury in the 
sprayed plats. 
Observations on the prevalence of the mealybug fungus were made 
in connection with this count. A dead infected individual here and 
there in unsprayed areas showed that the fungus had been respon- 
sible for the destruction of the colonies included under the caption 
" has been very abundant." In those colonies classed as " very abun- 
dant" the fungus was very noticeable at the time the count was 
made. On the other hand, in the sprayed area, except for one tree 
sprayed with lime-sulphur, no fungus was observed, and there were 
no indications that it had been there previously. A few dead infected 
mealybugs, however, were found upon the tree sprayed with lime- 
sulphur. 
In brief, this experiment shows that fungicides, with the possible 
exception of lime- sulphur, prevented the development of the mealy- 
bug fungus, which in turn permitted an unrestrained development 
of the mealybugs. In the grove where this experiment was per- 
formed the infestation was very scattered, as shown by the fact that 
of the 255 unsprayed trees, 185, or 72.5 per cent, were free from the 
insect. 
Considered from the standpoint of a period of years, the mealy- 
bug is relatively innocuous as a citrus pest, and it is believed that its 
commercial control during such periods is brought about by the 
natural enemies, chiefly the fungous parasite herein described. Sea- 
sons obtain, however, such as the summer of 1921, and to a certain 
extent that of 1920, in which this insect appears in numbers suf- 
ficient to arouse the attention of the citrus grower. There seem to 
occur more or less lengthy periods in which control exists to all in- 
tents and purposes, alternating with periods of much shorter dura- 
tion, lasting but one or two seasons, in which the insect threatens to 
become a serious pest. Numerical fluctuation of the mealybug is 
natural and unavoidable, for its control is largely brought about by 
natural enemies which are dependent for the perpetuation of their 
own species upon the presence of the hosts which they parasitize, the 
lack of which, particularly if the parasites are more or less specific, 
will cause them to disappear. It is very probable in the present in- 
stance that a great part of the fungus, which is extremely prevalent 
when the mealybugs are abundant, dies out for this reason, and in 
the period of recovery which follows, the host has the advantage 
and therefore increases in numbers until the parasite once again be- 
comes sufficiently abundant to check it. The grower is concerned 
only with those periods in which the insect threatens to injure his. 
fruit and trees. At such periods he can either resort to the employ- 
