170 



Hellebore. Hellebore consists of the finely ground roots 

 of Veratrum album, a plant of the order Liliaceae. It is 

 used in temperate climates for the control of soft-bodied 

 slugs and caterpillars, on certain plants, but will probably 

 have only a limited application in the tropics. Its proper- 

 ties are similar to those of the vegetable poisons already 

 mentioned, but it is not as strong in its effect. 



CONTACT POISONS. Contact poisons are generally more 

 difficult in preparation for use than the majority of stomach 

 poisons, since most of them are mixtures of several sub- 

 stances, which require care in their preparation. 



The effect of contact insecticides is to cause the death 

 of insects by clogging or closing the breathing openings, 

 (stigmata), by penetrating the stigmata and breathing tubes 

 and thus causing a fatal irritation, or by forming a thin 

 coating on the entire insect and sealing it down to the leaf 

 or bark on which it occurs. 



It will easily be seen, then, that for these to be effective, 

 the insecticide must be brought into contact with the insect, 

 careful application of the spray, wash or dust being most 

 essential to successful results. 



The materials which are most likely to be found useful 

 as contact insecticides, either alone or in combination, are 

 the following : whale-oil soap, fish oil, rosin, soda, soap, 

 kerosene, sulphur, and lime ; while pyrethrurn, tobacco, 

 hellebore, turpentine and hot water are all to be included 

 among the insecticides of this group. 



Whale-oil Soap. This is a very useful insecticide, 

 especially for plant lice, leaf-hoppers, thrips, mealy-bug, 

 white fly, and certain scale insects. It is also useful for 

 treating insects at the base of plants, in pots or garden beds, 

 and it may be used with good results on caterpillars and 

 other soft-bodied insects which feed in exposed situations. 

 It has the advantage of being easily prepared for use, and 

 the disadvantage, or what is considered to be so by many, 

 of being very foul-smelling. 



It is used in solution, in varying strengths. Palms and 

 other plants with tough leaves will suffer no injury from the 

 application of the stronger mixtures, while for tender- leaved 

 plants the strength may be much reduced. 



Whale-oil soap is prepared for use by merely being 

 dissolved in water, the proportions being from 1 ft. in 2 

 gallons to 1 ft. in 8 gallons, of water. 



