PETROLEUM-SOAP EMULSIONS. 301 



water, this emulsion kills insects and prevents their return much 

 longer than a simple emulsion. In South America flowers of sulphur 

 are incorporated in the emulsions. They have been successfully used 

 against erinose^. Galloway and Marlatt recommend adding a proper 

 quantity, 2-6 per cent, of petroleum to bouillie bordelaise. These mix- 

 tures are more stable than simple emulsions, they keep for eight days. 

 Of all the emulsions described, those made with soap and petroleum 

 are to be preferred. 



Use against Injurious Fungi. — Potato Scab. — This disease, char- 

 acterized by an enormous development of the periderm, is caused by 

 a special bacteria. It may be prevented if some hours before plant- 

 ing the soil be impregnated with an emulsion of soap 12^ lb., petroleum 

 4-5 gallons. This amount suflices for 24 square yards (Frank and 

 Kruger). 



Use against Coleoptera and their Larvae. — It is impossible to 

 enumerate all the insects overcome by petroleum. The following are 

 some typical examples : — 



Melolonthince (cockchafers). — The larvae of the cockchafers — Melo- 

 lontha vulgaris, the common cockchafer; Melolontha Hippocastani, the 

 horse-chestnut cockchafer; Melolontha Fullo, teasel cockchafer; Lachno- 

 stenia arcuata, red cockchafer — are destroyed, or at least so inconveni- 

 enced, by the presence of petroleum in the soil that they soon desert it. 

 This effect is best obtained by burying to a depth of 30 inches rags- 

 steeped in petroleum. Perkins, Alvood, Schoyen, and Marlatt ob- 

 tained satisfactory results by the use of aqueous or soapy emulsions. 

 They found that it was not enough to kill the larvae of these insects, 

 to sprinkle the soil around the plants with 3*5 per cent emulsions, for 

 the larvie descend into the untouched deep layers, from which they 

 ascend some time afterwards. The results are, on the contrary, ap- 

 preciable when the moment is chosen when the larvae have regained 

 the surface layers of the soil to dig deep narrow holes between the 

 rows of the young pine or spruce plantations or round the vine stocks, 

 in vineyards. A 20 per cent emulsion of petroleum is run into the 

 holes, which are then filled up with earth, and an hour afterwards, 

 sprinkled with water. Used in this way, petroleum destroys a great 

 portion of the larvae of these lamellicorns, and protects the plant for 

 a certain time against fresh attacks. In Norway, young plantations 

 of conifers are successfully protected by pouring into the holes pre- 

 pared before planting an emulsion of 1 part of petroleum with 13-15 

 parts of water. In America, Perkins advises spraying meadows with 

 emulsions, harmless to grasses, to free them from the larvae of the 

 Lachjiosterna and the Allorhina nit Ida. 



Elateridece (wire-worms). — The larvae resist the usual insecticides 

 better than soft-skinned larvae. Comstock and Slingerland found 

 petroleum emulsions without action on these larvae. Perkins regards 

 them as inefficient and Tarzioni-Tozzetti was only partially successful 

 with an emulsion of petroleum with fish oil. 



CurculonidcB (weevils). — To get quit of the anthonomes of flowers,, 

 and prevent them laying their eggs, very dilute emulsions of petroleum 

 may be used, sprayed on the flowers before flowering. Schilling oh- 



