76 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



If the tanks have only the slight slope required to ensure the flow 

 of water without a gush, the water introduced into the basins will 

 filter into the soil without moistening the surface layer. As soon as 

 the liquid is completely imbibed, the holes are filled with dry earth 

 and the soil is soon afterwards tilled and hoed. The large quantity of 

 water which these irrigations require renders the treatment almost 

 impossible. But when a spring with an output of a litre a second 

 (13*2 gallons a minute) is available the quantity of water produced 

 suffices to irrigate 10 hectares (25 acres). Underground insecticide 

 irrigations, although useful in all cases, are particularly favourable in 

 the hot countries of the South of France, where it is necessary to 

 ameliorate the hygienic conditions of the vine by moisture to enable 

 it to reconstitute its root system after being freed from the insect 

 which caused the disease. 



Schizoueiira lanigera, Hausm. (woolly aphis). — The disinfection of 

 the branches, as is done by applying various insecticides, is not 

 enough, for there exist underground hot-beds of infection which re- 

 infect the crown of the tree. Carbon disulphide, used in injections 

 round the plant, forms an excellent means of destroying the aphis 

 living on the roots. Taschenberg and Goethe have recommended the 

 use of carbon disulphide to destroy the colonies existing above ground. 

 They advise for this purpose the use of a stick, to the extremity of 

 which a lump of cotton-waste dipped in carbon disulphide is fixed. 

 The woolly aphis can thus be destroyed at all seasons without injuring 

 the apples. To get a good result the colonies must not be overlooked, 

 and to recommence the treatment some time after the first. Targioni 

 and Sorauer recommend soap emulsions for the same object, the first 

 a 2 per cent carbon disulphide one, and the second a 4 per cent one. 

 Gold's liquor, recommended for the destruction of the woolly aphis, 

 consists of 20 grammes of [spirits of ?] turpentine, 20 grammes of 

 carbon disulphide, and 60 grammes of curdled milk. Amongst the 

 underground ground lice that often occasion great damage are the — 



Schizoneura GrossularicB, Schule, which sucks the roots of the 

 gooseberry. 



Aphis Persicce, niger (the peach tree aphis). — This aphis causes 

 ravages in peach orchards in America. 



Tychea Phaseoli, Pass. — The presence of which, on the roots of 

 haricots, cabbages, and potatoes, sometimes causes them to perish. 

 All these insects may be combated like the phylloxera. The lice 

 which sometimes damage certain plants are successfully combated 

 when it is possible to cover the plant with an awning or a cloche (bell- 

 shaped vessel) under which a few grammes of carbon disulphide are 

 laid. According to Smith all the lice are killed in an hour. Even 

 after twenty-four hours' treatment at the ordinary temperature the 

 plant does not suffer. Soap emulsions, 2-4 per cent, have likewise 

 been applied in a general way, but these latter, which sometimes 

 succeed perfectly, may completely roast the leaves, chiefly those that 

 have been wounded. 



Coccides (cochineals, kermes). — In a general way the Coccides resist 

 carbon disulphide to a greater extent than the Aphides, but they do not 



