Materials and Formulas. 179 



loxera, the ground remaining covered with water for several 

 weeks during the winter, when the plants are dormant. It is 

 only in exceptional cases that water can be used in this manner 

 to advantage. 



The practice of dislodging insects by means of a stream of 

 water forcibly applied is confined almost wholly to florists. 

 Plants grown under glass may easily be kept clean in this man- 

 ner, provided the water may be used freely ; it is one of the 

 best remedies for mealy-bugs and similar pests. The presence 

 of red spider upon greenhouse plants is principally due to a dry 

 atmosphere, and no good gardener need be troubled by this 

 insect, unless some very good reason exists why the plants 

 should not be syringed or sprayed. A moist atmosphere will 

 also check the growth of certain fungi, but as a rule such condi- 

 tions favor their development. 



The value of hot water in destroying insect life has long been 

 known. If an insect be treated with water having a tempera- 

 ture of 125-130 F., it will succumb almost immediately, and 

 no injury to the plant will result. Rose chafers will yield 

 readily to this treatment, but great difficulty is experienced 

 in maintaining the proper temperature. A spray is cooled 

 instantly, and when a solid stream is used the operation is 

 slow and difficult. For this reason the remedy is little used. 



Cold water, that having a temperature little above freezing, has 

 been recommended against soft-bodied insects, as the cabbage 

 worm, but satisfactory results rarely follow such applications. 



WHALE-OIL SOAP. The value of this soap for destroying 

 insects was discovered many years ago. (See page 14.) The 

 oil from which the soap is made is probably the active prin- 

 ciple. The dissolved soap has proved itself to be of particu- 

 lar value in destroying scale insects when used at the rate of 

 1 pound in about 5 gallons of water. Mealy-bugs may also be 

 destroyed by such a solution, but care must be taken to see that 

 the insects are wet by the liquid. Plant lice are easily killed 

 with much weaker solutions, using 10 gallons to the pound. 



Whale-oil soap may also be highly recommended for use in 

 preparing emulsions of the various oils, since the union of two 

 good insecticides cannot fail to make the mixture more eii'ect- 

 ive than is either substance alone. The soap varies in price 

 from eight to twenty cents per pound. 



