THE PEAR THRIPS AND ITS CONTROL. 63 
Plowing during February and March, when adult thrips are coming 
out of the ground, is not practicable because of the usually heavy 
rainfall at this time, and because the ground breaks up into large 
instead of small clods, for which reason only a few thrips are killed. 
Then, too, plowing at this time seems to let the thrips out all at once, 
thus increasing rather than reducing their injury. Several orchards 
that have been kept under constant observation, which were plowed 
during February and early March, were very much more seriously 
injured than orchards of the same variety of fruit immediately 
adjoining which were not plowed at this time. 
The benefits of plowing and cross plowing have been so evident 
in every one of the several orchards treated that during the spring 
one could tell almost to a row, by the healthful condition of the trees, 
where the plowing began and where it ceased. 
A careful examination of the soil under prune trees, after plowing 
had been accomplished, showed that almost no thrips were present 
until a depth was reached where the plows had not cut. Below 
this point the usual numbers of thrips were found. 
SPRAYING. 
Spraying for thrips has proved wonderfully successful wherever 
proper sprays have been used and the work done with care and 
thoroughness, while indifferent and careless work or improper sprays 
are absolutely ineffective. The thrips must first of all be reached. 
This necessitates high pressure—125 to 180 pounds—and a rather 
coarse, penetrating spray. It is necessary also that the spray be 
directed downward into the buds, and not thrown at them from 
below or from the sides. It should be remembered that spraying is 
done, not to drive the insects away or to protect the tree from any 
possible future attack, but to kill those insects which are actually 
present on the trees. It may not be possible to reach all of the 
thrips which are concealed in the buds even with most careful spray- 
ing, but a very large percentage of them can be killed. Spraying 
into partly opened buds and blossoms theoretically seems impos- 
sible, but is found entirely practicable when a coarse, forceful spray 
is thrown down directly against the tips. A tower platform should 
be built over the spray wagon so that the tops of large trees can be 
properly sprayed. 
Almost all of the standard spray formulas have been thoroughly 
tested, and all except two have been eliminated. The bodies of 
the thrips, both adults and larve, are decidedly oily and strongly 
resistant to all sprays which do not readily assimilate the oil. For 
example, the lime-sulphur solution, which is very caustic, may be 
thrown onto the thrips, and it will merely gather in globules on their 
