INSECTICIDES AND THEIR USES 4I 



Nicotine extracts and pozvdcrs are extensively used by florists 

 as general fumigants for aphides, thrips, white fly, and other 

 small and soft-bodied insects in greenhouses. These extracts 

 are manufactured by a number of firms who advertise chiefly 

 in florists' journals. They contain a much larger proportion 

 of nicotine than decoctions, and are proportionately more ef- 

 fective. They are used in various ways : Dry fumigants are 

 placed in shallow pans and a few drops of kerosene poured on 

 to facilitate ignition. These burn slowly, producing a smudge 

 which is fatal to aphides and similar insects. The liquid prep- 

 arations are evaporated over an alcohol lamp, or are "painted" 

 on steam pipes, or hot irons are put into the receptacles. 



The amount of nicotine solution to use depends upon its 

 strength (varying from about 35 to 85 per cent, nicotine), the 

 plants to be treated, the size of the frames or greenhouse and 

 the construction of the latter, whether tight or loose. A pre- 

 liminary test, on a small scale, is therefore a prerequisite to the 

 use of a nicotine fumigant. Follow the directions accom- 

 panying the preparation used and increase or decrease the 

 strength as necessary. If cucumbers are being fumigated, a 

 smaller amount may be desirable. One of the most widely 

 known of these nicotine solutions has been used with great suc- 

 cess at the rate of 5 or 6 teaspoonfuls of the liquid to 8 quarts 

 of water vaporized in 5.000 cubic feet of greenhouse space. 

 Used thus on cucumbers at night it did not injure the plants, 

 while thrips which infested the plants were killed. Aphides 

 are more easily killed than thrips, while white flies require still 

 longer exposure and repeated applications. 



After treatment plants are carefully syringed with whale-oil 

 or similar soap and the house ventilated. A second fumigation 

 is sometimes given, allowing the tobacco smudge to remain over 

 night. A surplus of moisture is to be avoided, as it induces 

 spot, mildew, and similar fungous diseases. 



Sulphur, applied dry in the form of "flowers of sulphur," is 



