216 Commercial Gardening 



14. Paris Green (Emerald Green, French Green, Mitis Green). 

 This may be had in a powdered or paste (Blundell's) form, the latter being 

 the better. One ounce to 10 to 25 gal. water is used as an insecticide to 

 prevent attacks of Codlin Moth, in spring, and other pests. If used too 

 strong it will burn the leaves. This may be guarded against, however, 

 by adding to the liquid an equal or double weight of lirne in proportion 

 to the quantity of Paris Green used. By adding a quantity of whitening 

 to the solution it will be easy to see where the spray is distributed. 



15. Pearl Ash (Potassium Carbonate). This is made by boiling the 

 ashes of plants with water and evaporating to dryness. It is deliquescent 

 and very soluble in water. The strength varies from 40 to 85 per cent. It 

 is used as an insecticide and fungicide, 1 Ib. being sufficient for 10 gal. of 

 water. 



16. Pyrethrum (Dalmatian Insect Powder, Persian Insect Powder). 

 This powder is obtained by grinding the dried flowerheads of Chrys- 

 anthemum coccineum and C. cineraricefolium. The powder obtained 

 from unopened flowerheads is considered better, although more expensive. 

 The powder is used in various ways: (i) Simply by dusting over plants 

 affected with aphides, &c.; (ii) as a spray, 2| Ib. powder to 10 gal. hot 

 water; (iii) as a fumigant, by sprinkling the powder over hot cinders in 

 a greenhouse; and (iv) mixed with flour in the proportion of 1 part to 

 10 to 30, and dusted over the foliage. 



17. Quassia Chips. These are obtained from Picrcena excelsa. They 

 should be boiled for two or three hours to extract the bitter principle. An 

 excellent all-round insecticide is made from 1 Ib. quassia chips, 1 Ib. soft 

 soap, and 10 gal. water. The quassia chips, after boiling in a gallon or two 

 of water, should be strained off through muslin or sacking, and mixed with 

 the dissolved soft soap, making the whole solution up to 10 gal. Trees 

 in fruit, Cucumbers, &c., should not be sprayed with quassia solution, as 

 it imparts a bitter flavour. 



18. Quicklime applied in the form of a powder is a good remedy 

 against slugs and snails, and is also a useful soil constituent. In a slaked 

 form lime is also useful, but two or three applications in succession are 

 needed to kill slugs and snails. It is used with such fungicides and 

 insecticides as Bordeaux Mixture, Paris Green, &c. 



19. Sodium Cyanide. This is used in connection with hydrocyanic 

 acid gas for vaporizing greenhouses, as stated above, p. 169. 



20. Soft Soap (also known as Whale-oil Soap, Train-oil Soap, Fish- 

 oil Soap, and Potash Soap). This is one of the cheapest, simplest, and 

 at the same time most effective insecticides used for horticultural purposes. 

 Good samples should be free from resin and contain not less than 8 per 

 cent of potash. It dissolves readily in water, and 1 Ib. to 4 gal. serves to 

 kill aphides, mealy bug, scale, red-spider, &c. Soft soap is mixed with 

 various other insecticides and fungicides, as may be seen from the formulae 

 given above. 



21. Sulphide of Potassium or Liver of Sulphur. This has become 



