66 IXSK(TIfIl)]:s. FTNGICIDES, AND WEED KILLERS. 



the cockchafer, the white worm, on condition that it be a})pUed 

 at the right time and intelligently. It is even more active than 

 benzine, recommended under similar circumstances by Vermorel. 

 Falconnet and Treyre, who were the first to use this insecticide as far 

 back as 1883, pointed out the absolute efficiency of this treatment. 

 There does not exist for this particular application of carbon disulphide 

 precise data as to the depth to which the injection should be made. 

 The white worm travels, in fact, constantly in the soil ; it rises and 

 descends according to the hygrometric condition of the soil, and the 

 temperature. In winter it buries itself at a depth where it cannot be 

 reached by insecticides, in summer it ascends, on the contrary, into 

 the superficial layers where disinfection cannot reach it, the tension 

 of the vapour of carbon disulphide not being sufficient, and the larvae 

 often finding enough air to escape asphyxia. It is thei'efore necessary 

 to seize the moment when the larvae are about 30-40 centimetres (12- 

 16 inches) from the surface of the soil, that is to say, about the month 

 of October or November, when it descends, or in the month of 

 February, when it I'e-ascends into the surface layer to commence its 

 x-avages. So that the treatment may be followed by a complete re- 

 sult, it is necessary that carbon disulphide invade the whole zone of 

 soil occupied by this dangerous larva ; the treatment ought, therefore, 

 to be preceded by trenching with the spade which should determine 

 for the moment the spot occupied by the white worm. The in- 

 jection is regulated in such a way that carbon disulphide is volatilized 

 appreciably in that zone, which will be reached by working 5 centi- 

 metres further down. It is useless to treat the soil during the period 

 of the year the perfect insects appear, and which current language 

 designs as beetle seasons, the laying being done in the month of June, 

 the white worms, which are hatched a short time afterw^ards, do not 

 yet cause appreciable damage, and moreover these young larvae reside 

 so near the surface soil that it would be difficult to attack them. 

 The treatment is put off generally until the month of February of the 

 second year, and the time chosen the moment the larvae appear on the 

 surface of the soil. The laying of the beetle, occurring only once in 

 three years, there is only one favourable period occurring in this inter- 

 val. It only lasts a few months. As the treatment costs 120 francs 

 per hectare, say nearly £2 per acre, the annual expense will only run 

 to 40 francs per hectare, say 13s. per acre. It can therefore be applied 

 in market garden or in nurseries without entailing great expense. It 

 has the advantage of killing at the same time rats, mice, moles, mole 

 crickets, grey worms, and all the parasites which injure our crops. 

 Falconnet and Treyre have found that the dose of 10 grammes per 

 square metre (154 grains per 40 inches square) is sufficient in orchards 

 to kill the larvae in the deep layers of the soil. Vermorel and Couanon 

 recommend on the contrary a stronger dose, that is to say, 20-28 

 grammes per square metre (| to 1 oz. per 40 inches square). To 

 spread this insecticide use is made of a pal-injector, which is regulated 

 to distribute 5 grammes (77 grains) at a time in holes placed 50 centi- 

 metres (20 inches) apart in every direction. But the number of holes 

 and the dose varies according to the nature of the soil and the kind 



