12 
wet or varnished over in a much shorter space of time than when a 
finer spray is used, and all of the operators that I have conversed with 
on this subject were unanimous in their statements that the time thus 
saved much more than compensated for the somewhat larger quantity 
of the preparation that was required when the coarse spray was em- 
ployed as compared with a finer spray. The evidence, therefore, 
appears to be decidedly in favor of a rather coarse spray. 
But whatever may be the character of the preparation used, or the 
nature of the spraying nozzle employed, the success of the operation 
will depend very largely upon the thoroughness with which the prepa- 
ration has been applied. In the case of small trees it is comparatively 
easy to wet every part of them, but when the trees are 20 feet or more 
in height and have not been properly pruned it is not only difficult but 
quite impossible to wet every portion of them; and, unfortunately, the 
tendency is to use as little of the preparation upon the tree as is abso- 
lutely necessary. On tall trees the operation of spraying is made more 
effectual by the use of tall ladders, so that the various parts of the trees 
can be sprayed from above as well as from below. 
It is well known among those who have had any experience in trying 
to destroy the Red Scale with sprays of any kind that the scale insects 
which are located upon the fruit are less affected by the different 
liquid preparations than those located upon the leaves or bark. 
The reason for this appears to lie in the fact that those located upon 
the fruit, having an abundance of food always within easy reach, are 
more healthy and vigorous than those located upon the other parts of 
the tree, and consequently are better prepared for resisting the destruc- 
tive effects of the spray. That healthy, vigorous insects 2re capable of 
resisting the effects of a destructive agency that has proved fatal to 
their less vigorous comrades there can be no doubt. An instance of 
this kind is given in my report to Professor Riley for the year 1888, as 
published in the Annual Report of this Department for that year. On 
page 128, in speaking of the effects of arseniuretted hydrogen gas upon 
the Fluted or Cottony-cushion Scale (Icerya purchast, Maskell), the state- 
ment is made that “Subsequent experiments made upon perfectly 
healthy trees and insects showed that when the gas was used strong 
enough to have proved fatal to all of the Icerya on the neglected trees 
it did not kill one-half of those on the vigorous trees.” Owing to this 
fact it would be advisable to refrain from irrigating and cultivating in- 
fested orange trees for several weeks before spraying them, were it not : 
for the other fact that in the case of bearing trees such a course would 
seriously interfere with their bearing qualities or operations. Unlike 
deciduous fruit-trees, our citrus trees do not take a rest of several months’ 
duration between the ripening of the fruit and the blossoming of the 
trees for another crop; only a few weeks at the most intervening between 
these two periods in the case of orange trees, while on healthy bearing 
lemon trees both blossums and fruit are to be found at every season of 
the year. 
