254 AGRONOMY 



Remedies against sucking insects. Poisonous sprays have 

 no effect upon insects which suck the juices out of plants. 

 These insects must be killed by suffocating them in various 

 ways. One of the best and cheapest insecticides for this pur- 

 pose is Persian insect powder, for sale by all druggists. It may 

 be applied by means of a small bellows, and is very efficient in 

 clearing insects out of small crevices where sprays have diffi- 

 culty in penetrating. The standard spray is kerosene emulsion, 

 made by adding 2 gallons of kerosene to 1 gallon of hot 

 soft water in which half a pound of soap has been dissolved. 

 This is then very thoroughly churned in order to make an 

 emulsion that will mix with water. When wanted for use, 

 it is diluted with from 10 to 30 gallons of soft water. The 

 strong solutions are used for scale insects ; the weaker ones 

 for plant lice. Whale-oil soap is often used for house plants 

 and greenhouse specimens. The spray is made by dissolving 

 2 pounds of whale-oil soap in 1 gallon of soft water. A strong 

 soapsuds, made from any kind of soap (naphtha soap pre- 

 ferred), is also useful. Tobacco water is made by pouring hot 

 water over a quantity of tobacco stems and allowing them to 

 steep for several hours. This liquid is then diluted and used 

 as a spray. In plant houses, cold frames, and the like, tobacco 

 smoke is often relied upon for killing aphids. Carbon disulphide, 

 which may be purchased of the druggist, is an ill-smelling 

 liquid that turns to gas as soon as exposed to the air. It is 

 heavier than air and may be used to exterminate ants and 

 other vermin that burrow underground. A little of the liquid 

 is poured into the entrance of the burrow, which is then 

 stopped up. Carbon disulphide is very inflammable and should 

 not be used where there are fires of any kind. In the larger 

 operations of the horticulturist hydrocyanic gas is sometimes 

 used. It is a deadly poison and must be handled with great 

 caution. In fumigating with this, a tentlike covering is placed 

 about the entire plant and filled with the gas. 



