6 FARMERS” BULLETIN 674. 
REMEDIES FOR THE CITRUS THRIPS. 
Certain measures against the citrus thrips have been persistently 
recommended in spite of abundant evidence of their inapplicability. 
These are usually directed against the pupal stage and consist in the. 
application of insecticides to the soil, breaking the soil up fine to 
destroy the insects supposedly pupating there, and burning dead 
leaves and trash, which accumulate under the trees, to destroy the 
pup. These methods are worthless for the reason that the thrips 
Fic. 4.—Resin-wash injury to half-grown oranges sprayed for the citrus thrips. (Original.) 
do not go into the soil at all, and only a varying and often small 
percentage of them pupate in the trash. Fumigation with hydro- 
cyanic-acid gas will reach and kill only the larve and a small 
number of adults, and is accordingly too expensive to use. Dis- 
tillate-oil emulsions and proprietary emulsions containing distillate, 
even when used as weak as 2 per cent, stain the ripe oranges, and 
are otherwise so injurious that it is considered unsafe to use them. 
Commercial lime-sulphur is not noticeably injurious when used at 
less than 1 part to 28 parts of water. . Resin wash can not be safely 
used on orange trees at any strength. Where the resin mixture 
comes into contact with the fruit the epidermal cells are killed and 
