PETROLEUM SPRAYS. 297 



pure petroleum, and declared against its use in arboriculture, remarking, 

 however, that the 25 per cent emulsions if they have not on kermes 

 such a radical action as pure petroleum, yet they completely destroy 

 them if the treatment be repeated and used regularly. 



Ocneria dispar, Sch. (gypsy moth). — Petroleum is more active than 

 the tar generally used for the destruction of the eggs of this injurious 

 butterfly. The destruction of the eggs is complete ; a jet apparatus is 

 used to localize the action of the pure petroleum on the aggregation 

 of eggs alone. 



Cossus ligniperda {Cos.ms gdte-bois) (goat moth). — Introduce 

 petroleum into the tunnels dug in the trunk of trees and plug with 

 mastic (Truelle). 



Vespa {Guepe) (wasp) and Formica (Fourmi) (ants). — Pure 

 petroleum is greatly recommended for the destruction of wasps' nests 

 underground. Early in the morning, before the exit of the wasps, 

 about a glass of petroleum spirit is run into the nest through the 

 aperture, then the aperture is plugged, first with a pad drenched with 

 petroleum, then with earth so as to prevent the vapours of petroleum 

 from escaping. Carbon disulphide is, however, better than petroleum 

 spirit. 



Schizoneura lanigcra, H. (woolly aphis). — Amongst the eighty-one 

 methods recommended in 1903 to destroy this aphis, Thiele found 

 that only pure petroleum, petroleum emulsion with soft soap, the 

 alcoholic solution of corrosive sublimate, caihon disulphide, amylic 

 alcohol, tar, and a mastic of lime and cow-dung, were capable of 

 entirely destroying this aphis. All the other methods had only a 

 temporary effect. 



Phylloxera vastatrix (phylloxera of the vine). — Mouillefert found 

 that petroleum had an immediate action on this aphis, biat that its 

 vapours alone acted slowly. Used to overcome the phylloxera on vines 

 in pots the results were excellent, but there was complete loss on vines 

 ■on the large scale. The aphis still lived on stocks which received up 

 to 150 cubic centimetres of petroleum. Petroleum is thus much less 

 energetic than carbon disulphide, for its diffusion through the soil is 

 bad, so that it cannot act at a great distance from the spot where it 

 was injected. The coating of the roots, proposed in 1872, was rejected 

 as too dangerous to the health of the vine by the commission to 

 investigate the different processes recommended to overcome the phyl- 

 loxera. It would appear, however, that the disinfection of the vine by 

 petroleum is possible by steeping the roots of uplifted stocks in a 

 bucket filled with crude petroleum ; the stocks replanted in a soil dis- 

 infected with petroleum yield vines the health of which is perfect and 

 the roots of which show no more phylloxera. 



Melolontha vidgaris (cockchafer). — The diffusion of petroleum 

 through the soil is recognized as insufficient to destroy injurious 

 insects or their larvae beyond a very narrow zone round the hole into 

 which petroleum was injected ; it was, however, found that the vapours 

 are disagreeable to the insects, and that these desert a field smelling of 

 petroleum. Doming and Decaux utilized this property to free fields, 

 not only of white- worms, larvae of the cockchafer, but also grey-worms, 



