REMEDIES FOR INJURIOUS INSECTS 247 



able, however, to use other insecticides in the case of vegetables 

 soon to be eaten, and thus avoid all appearance of danger. 



The strongest repugnance is felt in many parts of England 

 to any kind of application of arsenic to food crops. A very 

 similar feeling formerly prevailed in the United States, but has 

 been dispelled by the frequency of arsenical treatment, and the 

 practical absence of injury to man or the higher animals. 



2. Petroleum emulsion. — Crude petroleum, applied as fine 

 spray is occasionally useful — e.g. in destroying egg-clusters of 

 the gipsy-moth in stone walls. For application to living plants 

 an emulsion may be employed, such as the following : — 



Soft soap is dissolved in twice its bulk of boiling water. 

 While the solution is still boiling hot petroleum is added equal 

 to half the bulk of the soft soap, and the whole thoroughly 

 mixed with a force-pump. The emulsion is diluted imme- 

 diately with an equal bulk of cold water and kept till required. 

 It may now be used as a wash for dormant wood, but should 

 be further diluted before application to foliage or young wood 

 (say two parts of water to three of emulsion). 



3. Soap and tobacco solution. — One part of soft soap should 

 be dissolved in sixteen parts of hot water : when cold, add one 

 part of strong tobacco decoction. For application to dormant 

 wood, or (further diluted) to growing tissues and to earth con- 

 taining root-feeding larvse. 



4. Resin soap solution. — Broken up resin is dissolved with 

 washing soda and boiling water in a kettle. Three parts- of 

 soda will dissolve about four parts of resin. Enough water 

 should be added to cover the resin, and the soda should be 

 dissolved before heat is applied. When the resin is completely 

 dissolved and a clear, brown mixture (a) obtained, more water 

 may be added, little by little, with constant stirring, till the 

 solution is sufficiently dilute for use. If the strong solution (a) 

 is diluted with twice its bulk of water it can be kept indefinitely, 

 and further diluted before application. Fifteen parts of water 

 to one of resin make a strong wash, twenty parts of water to 

 one of resin a wash suitable for application to living tissues. 



This preparation is particularly useful in the case of Aphids 

 and other soft-bodied, sedentary insects. 



Poisonous sprays should not be applied to fruit-trees in 

 bloom, as there is risk of destroying bees and other useful 

 insects, as well as of damaging the flowers: 



