64 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



over sulphurous acid employed in like conditions, the latter having 

 the drawhack, according to Balland, of removing from the gluten the 

 special qualities which enable it to be used in bread-making. 



Destruction of Aerial Parasites. — When the plant attacked is of 

 no great height it is covered with a tent of imper neable oil- cloth, or 

 by a zinc bell, or better still, by half a barrel (petroleum), as is done 

 in the treatment of vines by sulphurous acid. By this means an 

 atmosphere containing vapours of carbon disulphide can be created 

 around the tree, capable of rapidly destroying the parasites without 

 injuring the plant, whilst, according to Eitter and Moritz, the 

 phylloxera under its gallicole form and its winter egg, is killed in half 

 an hour at a temperature of 20°-30'' C. (GS^-SG" F.) in an atmosphere 

 containing a sufficient dose of sulphide. The vine supports without 

 suffering the action of this gas for twelve hours at 20° C. (68° F.). 

 It is, however, to be observed that the longer the duration of the 

 treatment, and the higher the temperature, the greater is the action 

 of the sulphide on the plant. The dose of sulphide to use ought never 

 to be greater than 0-5 to 1 per cent. For this purpose 50-100 grammes 

 of sulphide per cubic metre are placed in a cloche or in a flask hooked 

 to a branch, or on the soil in a saucer. In hothouses the atmosphere 

 must not contain more than 0*5 per cent of carbon disulphide. To 

 destroy the larvae of xylopliages, such as the larvae of the Saperdes, 

 the grubs of Cossus, and of Sesia, a poisonous atmosphere is formed 

 in the burrows they make in the trunks of trees. To imprison the 

 vapours it is necessary to close the burrows with some sort of mastic. 

 This treatment is in no way prejudicial to the plant. Where fumiga- 

 tion in an enclosed space is impracticable, recourse is had to pul- 

 verizations with soapy emulsions, made in the same way as those with 

 a petroleum basis, and containing 2 per cent of sulphide, the limit of 

 innocuity on the tender parts of the plant. In certain cases the in- 

 vaded spots are plastered with the pure sulphide by means of the brush, 

 and that chiefly when it is a case of the destruction of the woolly 

 aphis {Schizoneura lanigera). The action of the sulphide employed 

 in this way is not so perfect as in a hothouse, or under a cloche, its 

 rapid evaporation not allowing of a sufficiently long action which thus 

 often allows the parasite to escape death. 



Use against Cryptogam ic Diseases. — Deniatophora necatrix, 

 Hartig. — Jean Dufour, Director of the Station Viticole de Lausanne, 

 succeeded in arresting Bhizoctinia of the vine by applying carbon 

 disulphide at the rate of 200 grammes per square metre (say about 

 7 oz. per 40 inches square), after having removed the diseased roots. 

 According to this eminent observer carbon disulphide not only acts 

 by destroying the mycelium of the fungus in a great measure, but it 

 also imparts greater vitality to the vine. The latter, rendered more 

 vigorous, resists afterwards the action of the fungus which may have 

 escaped the destructive treatment. Oberlin and Foex believed that 

 the improvement in soils got by the use of the exterminating treat- 

 ment against phylloxera is due chiefly to the destruction of the 

 mycelium of injurious fungi which intervening crops are not capable 

 of eliminating, because they can live if need be just as well as 



