26 



Insecticides. 



Almost entire reliance is placed in America on caustic 

 insecticides, or those that act externally, for the subterranean 

 insects living on the roots of plants, including" both sucking 

 and biting insects, such as maggots in roots, root lice 

 (aphides), etc., as also the surface caterpillars. The insecticide 

 must be one that will go into solution and be carried down by 

 water. Of this sort are the kerosene emulsions, and potash 

 fertilisers such as kainit. Some simple remedies which have 

 been found useful are the application of strong soap or 

 tobacco washes to the soil about the stem ; or soot, ashes, or 

 tobacco dust buried a.bout the roots ; lime and gas lime are 

 also thus employed. But in the case of some underground 

 insects, notably wireworms, the remedies are of but slight 

 value. As a means of destroying root-lice, particularly the 

 woolly aphis, the most generally recommended measure is 

 hot water, applied at nearly boiling point about the base of 

 the trees, in sufficient quantity to wet the soil thoroughly to 

 the depth of several inches. As much as possible of the 

 surface soil should be first removed. The injection of bisul- 

 phide of carbon into the soil around the infected roots has 

 also proved most beneficial. A preventive measure which has 

 also met with success against this insect is the placing of 

 tobacco dust in the trenches in which seedlings are planted, and 

 in the holes dug for young trees. For large trees, from 2 to 

 5 lbs. of the tobacco dust (a waste product of tobacco factories) 

 is distributed round the tree to a distance of two feet, from 

 four to six inches of the surface soil being first removed. 



Another valuable wash, and one which should be used by 

 all orchardists, is the caustic alkali wash. This is employed 

 during the winter, February being the best month in Great 

 Britain. The effect of this wash is wonderful in an old orchard ; 

 it removes all the moss and lichens from the trees, and thus 

 destroys the winter quarters of many hibernating insects, kills 

 many of the dormant insects, and also destroys the eggs of 

 some pests, such as those of the Apple Sucker [Psylla malt), 

 and those of certain mites and aphides. It is made by dis- 

 solving 1 lb. of caustic soda and 1 lb. of carbonate of potash 

 in water, and adding the same to 10 gallons of soft water and 

 I lb. of soft soap. 



