4 



Insecticides. 



as cross-fertilisers. Thepetalsof the blossoms are also-damaged 

 ~by arsenites. In such cases, where it is undesirable to use 

 ■arsenicals, recourse may be had to the remedies employed 

 against other insects ; although these are not generally so 

 effective against the biting insects as the direct poisons, 

 when the season permits of the safe application of the latter. 



Against extarnal sucking insects, " contact " poisons, and 

 substances which render their surroundings disagreeable, are 

 the chief methods in use. 



Any good soap is effective in destroying soft-bodied 

 insects, such as aphides. The soaps made of fish oil 

 ■and sold as whale-oil soaps are often especially valuable, 

 4:,ui variable in composition and merits. A soap made 

 with caustic potash rather than caustic soda is recom- 

 mended, as it yields a liquid in dilution more readily sprayed 

 and more effective against insects. For plant-lice and 

 delicate larvae, a strength obtained by dissolving half a 

 pound of soap in a gallon of water has been found sufficient. 



Pyrethrum powder acts externally on insects through their 

 breathing pores, and is fatal to many forms both of biting 

 and sucking insects, but is not poisonous to man or the 

 higher animals. Its chief use is against household pests and 

 in greenhouses and small gardens, where the use of arsenical 

 poisons is not advisable. It is usually applied as a powder, 

 preferably in the evening so as to be retained bv the dew. 



Flowers of sulphur is used against many plant mites, such 

 as the red spicier ; chiefly in the form of a powder when the 

 foliage is damp. Sulphur is most successfully applied as a 

 wash combined with paraffin emulsion. Liver of sulphur is 

 the best form to use. 



The standard remedies against aphides and scales are, 

 however, emulsions of kerosene or petroleum oil with soap 

 The crude oils are said to be valuable against many pests, 

 but the greater safety of the emulsions has resulted in the 

 general adoption of these latter, as the pure oil, especially if 

 carelessly used, may result in serious injury to the trees. 

 The following are the proportions recommended for the 

 kerosene emulsion in America : kerosene, 2 gallons ; whale 

 oil soap, J lb. (or soft soap, 1 quart) ; water, 1 gallon. This 



