308 The Spraying of Plants. 



the material does not take fire, for this means instant death to 

 all plants reached by the fumes. 



If, in spite of the above precautions, fungi are still present 

 to an injurious extent, the next plan to follow is to apply some 

 of the standard liquid fungicides to the threatened plants, pre- 

 ferring those remedies which are clear solutions, for these dis- 

 figure even the most delicate colors to only a very small extent. 

 If this does not prove effectual, the plants should be thrown 

 away, and the grower might do well to try some other business. 



INSECTS INFESTING PLANTS. 



The number of different insects injurious to greenhouse plants 

 is rather small, although the number of the individuals of each 

 kind may be large enough. These creatures for the most part 

 require different methods for their extermination, and each of 

 the more important will be treated in detail. 



Aphis; Green-fly; Plant Lice. Description. These sucking 

 insects are too well known to require description, for they attack 

 nearly all greenhouse plants. They reproduce with extreme 

 rapidity, and must therefore be continually watched. Affected 

 leaves generally curl, the insects being found on the under side. 

 When the stems are attacked, frequently no external sign of 

 the insect's presence is visible except the insect itself. 



Treatment. Insecticides which kill by contact must be em- 

 ployed for destroying the aphis. Kerosene emulsion, pyre- 

 thrum, tobacco water, etc., may be used with success. But the 

 most common method of clearing a house of these creatures is 

 to fumigate with tobacco stems. A common coal scuttle will 

 answer the purpose well; when filled with the stems it will 

 supply smoke sufficient for a house containing from three thou- 

 sand to five thousand cubic feet. The amount to use will vary 

 with the tightness of the house and the quality of the stems. 

 The stems should be sufficiently moist to prevent them from 

 blazing. They may be ignited very easily with some paper or 

 shavings. If the house is a very tight one, it is well to admit 

 air after the fumes have been in about an hour, but in the ma- 

 jority of establishments this point takes care of itself. If only 

 few plants are to be treated, they may be placed singly under a 

 paper flour-sack or in a box, and then smoked, care being taken 

 not to use too much tobacco. Some commercial preparations of 



