310 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



injurious action of the lime from acetylene factories used in place of 

 ordinary lime to coat trunks of fruit trees. 



Destruction of Insects. — Melolonthides (cockchafers). — Scri- 

 baux and Chuard recommend acetylene against the enemies of 

 crops. They propose to incor])orate in the soil, preferably deep down, 

 a sufficient quantity of calcium carbide in small pieces, which by the 

 moisture of the soil would be decomposed into acetylene. This decom- 

 position occurs slowly and gradually. An insecticide gas is formed 

 capable of occupying a considerable volume of the soil treated. Weak 

 doses in Germany had no effect. Pieces of carbide of about 50 grammes, 

 say If oz., buried 8 inches down every metre is not enough, as 1 kilo- 

 gram only yields 300 litres of gas (1 lb. yields 30 gallons). 



Phylloxera vastairix (phylloxera of the vine). — Chuard tried the 

 cultural treatment of the vine against phylloxera by means of calcium 

 carbide. His trials in the neighbourhood of Annecy show that vines 

 treated with carbide exhibit a greater vitality and vigour than the 

 neighbouring untreated stocks, and on examining several stripped stocks 

 the phylloxera was absent. The process consisted in stripping the 

 roots and adding 100 grammes, say 3-| oz., of coarsely crushed carbide. 

 Trials in Germany on the contrary proved that carbide is unable to 

 overcome the phylloxera. The question is far from decided, and it is 

 very possible that in carbide we possess an excellent insecticide capable 

 of freeing crops from underground parasites. 



