138 



sensitive to injury than the exposed parts. As a precaution, earth 

 should be banked up round the base of the tree, and only sufficient oil 

 should be used to moisten the surface of the foliage and bark without 

 any surplus to run down the stem. 



Mixtures of kerosene and water have been largely employed in 

 America, and elaborate machines devised for ensuring the proper mix- 

 ture of the two ingredients. But under any circumstances their effec- 

 tiveness does not compare favourably with a properly compounded 

 emulsion. 



Referring again to one of Mr. Marlatt's reports, * 1 find it stated 

 that 1 kerosene mixed with water is not nearly so powerful an insecti- 

 cide as the kerosene soap emulsion. It does not remain nearly so- 

 long on the plant, and is not nearly so effective an insecticide 

 at the same strength of oil. The heavier soap or milk emulsions kill 

 more effectively, which is, perhaps, explained by the heavier liquid ac- 

 tually bringing more oil in contact with the insect, and also by its 

 greater permanency.' Taking everything into consideration, neither 

 kerosene, nor mixtures of the oil and water, can be recommended for 

 general use at any rate in the tropics. 



Resin Washes. — These are used extensively in California to remove 

 scale insects from fruit trees. The formula (taken from Bulletin, No. 

 9 of the U. S. Department of Agriculture) is as follows : — ' The summer 

 wash usually contains twenty pounds of resin, five pounds of crude 

 caustic soda (seventy-eight per cent.) or three and a half pounds 

 of the ninety-eight per cent., and two and a half pints of fish oil. The 

 winter wash contains thirty pounds of resin, nine pounds of crude soda, 

 and four and a half pints of oil. The ingredients are boiled in about 

 twenty gallons of water for two or three hours, hot water being occa- 

 sionally added until fifty gallons of solution are made. This, for 

 both formulae, is diluted to one hundred gallons before application to 

 trees. Greater efficiency is believed to come from long boiling of the 

 mixture, and it is preferably applied hot. It is used on deciduous trees 

 for the black and San Jose scales, and on citrus trees for the red and 

 black scales; but the dense foliage of the latter renders thorough spraying 

 difficult except for young trees, and fumigation is much preferred. 

 An improperly made resin wash is also apt to spot the fruit of the 

 orange. . . . 



Carbolic Acid. — Crude carbolic, phenol, Jeyes' fluid, and similar 

 compounds, all have insecticidal properties. Carbolic acid itself has 

 been found inefficient except when applied in such strength as to seri- 

 ously damage the plants. I find that phenol and Jeyes' fluid (which 

 appears to be much the same thing) are effective against Orthezia, 

 4 mealy bugs,' and most species of Lecanium. A mixture containing 1 

 part of Jeyes' fluid to 20 of water,applied to a Thunbergia bush attacked 

 by Orthezia, was fatal to more than 90 per cent of the insects, but 

 resulted in the death of the terminal buds of the plant. It had no bad 

 effect upon the more mature leaves and shoots. The application did not, 

 however, prevent the subsequent hatching of the eggs in the ovisacs of 



* Bulletin No. 9 (New Series), U. S. Department of Agriculture (Divisioa 

 of Entomology.) 



