THE CITRUS THEIPS. 37 
centage of the thrips can be killed by spraying with this solution, and 
there is a further effectiveness due to its decomposition for a long 
period after deposition on the leaves. In orchards sprayed with 
good lime-sulphur the sulphurous odor is often strong for two months 
or more after the applications. The decomposition products repel 
the thrips, which are slower to reinfest orchards so sprayed than 
those sprayed with solutions that soon evaporate and leave no trace. 
Tobacco extracts when used at the proper strengths are also very 
effective. Both tobacco extract and lime-sulphur, when mixed to- 
gether, are effective in weaker solutions than when diluted with water 
alone. Contrary to expectation, the addition of soaps to tobacco 
extract did not give increased value to the tobacco in these tests. 
Soap solutions used alone appear to be worthless at the dilutions 
tested. 
Resin wash at any strength practicable for use on the orange trees 
in this section is worthless. At the greatest strength used in these 
experiments it failed to reduce thrips injury to an extent worthy of 
attention. It is, furthermore, very injurious to fruit and foliage. 
Plain water spraying was utterly ineffective, demonstrating that 
merely striking the thrips with a liquid at high pressure to wash 
them from the trees has no appreciable effect in diminishing their 
numbers. A few hours after spraying with water there remained 
on the trees as many living, active thrips as before spraying. 
INJURIES TO CITRUS RESULTING FROM SPRAYING. 
INJUKY FKOM DISTILLATE-OIL EMULSION. 
In experiments conducted in 1910, emulsions containing 2 per cent 
of distillate oil caused severe staining to ripe oranges. Dark streaks 
were formed on the rind where the liquid had collected in drops and 
run down. A patent spray emulsion caused more staining than the 
home product at the same strength. 
INJURY FKOM EESIN WASH. 
On July 20, 1911, about two weeks after the final spray applica- 
tion, injury appeared from the resin wash in plat 18, Series I. About 
3 per cent of the leaves had turned brown and fallen and most of 
the oranges had become spotted with the varnish. In some cases the 
varnish had collected in drops and run down over the surface, finally 
drying to a hard, gummy substance. By September 25 the injury 
apparently had reached its highest degree and was serious in all 
three plats, though noticeably decreasing with the greater dilution 
of the wash. The epidermal cells of fruit protected from the direct 
rays of the sun were killed and a shallow, brown scab was formed. 
This scab often peeled off, leaving a film of light gray-green tissue 
