INSECTS INJURIOUS TO CITRUS FRUITS 625 



A large percentage of the thrips can be killed by spraying with this 

 solution, and there is a further effectiveness due to its decompo- 

 sition 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 together, 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 dimin- 

 ishing their numbers. A few hours after spraying with water 

 there remained on the trees as many living, active thrips as 

 before spraying." 



The Florida Flower Thrips * 



The Florida Thrips is larger than the true citrus thrips, being 

 about one twenty-fifth of an inch long while the other is frequently 

 less than one-half that size. It is of a yellowish or yellowish-red 

 color and may be observed most easily in or about the blossoms 

 of the orange. It injures the fruits and plants in much the same 

 way as does the citrus thrips but is more likely to destroy the 

 blossoms or the fruit just as it is setting by making its way down 

 into the flower to the ovary which it attacks. Its injury is more 



*Frankliniella bispinosus Watson. 



