THE GREENHOUSE THRIPS. 9 



treated, as there is considerable ditlerence between various plants in 

 their resisting power to this gas. 



Spraying with nicotine liquids. — Nicotine extracts diluted with. 

 water, if carefully appUed to plants, will kill large numbers of the 

 greenhouse thrips, but the great objection is that many of the insects 

 are not hit by the spray, and therefore the plants become reinfested 

 in a short time. 



Spraying with Tcerosene emulsion} — It is quite possible that kerosene- 

 emulsion spray will be effective against the greenhouse thrips when 

 used at the strength of 1 part of stock to 10 parts of water, and it 

 costs considerably less and is more readily obtained than the nicotine 

 preparations. It should be very carefully prepared and used experi- 

 mentally at first until the effect on the foliage of the different plants 

 is noted. Care should also be taken to prevent quantities of emulsion 

 from collecting around the roots. 



Water spray. — Frequent treatment uith a stiff" spray of water from 

 a garden hose or syringe will tend to keep this insect down, but unless 

 there are only a few plants it would be better to use one of the other 

 remedies. 



Any treatment for this insect should be repeated in from 7 to 10 

 days to destroy the young larvae that have hatched from the eggs. 

 This should be sufficient, but it may be best to give a third treatment 

 in another week or two. 



Treatment of trees in the open. — In the case of injury to tlie various 

 subtropical fruits it is recommended to spray the foliage thoroughly 

 with a nicotine spray. A tobacco extract of 2f per cent of nicotine 

 sulphate, diluted at the rate of 1 part to 60 parts in a 6 per cent 

 distillate-oil emulsion, has given such good results agamst the pear 

 thrips that this treatment should be tried.- 



Approved : 



James Wilsox, 



Secretary of Agriculture. 



Washington, D. C, April 19, 1912. 



1 For the method of making emulsions, see Farmers' Bulletin 127, or Cir. SO, Bur. Ent., U. S. Dept. Agr. 



2 Full direftlons for mixing this spray are given in Cir. 131, Bur. Ent.. U. S. Dept. Agr., pp. 8-9. 



ADDITIONAL COPIES of this publication 

 -iA. may be procured from the Superintend- 

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