1944 



ENCYCIiOPBDIA OF PRACTICAL HORTICULTURE 



ing to tlie small door, and the rest of tlie 

 trays extending clear across the box, be- 

 ing about five inches apart. Such a box 

 will hold from 1,500 to 2,000 loose plants, 

 placing only one layer on a frame, which 

 permits a quick and thorough diffusion 

 of the gas. 



The only other apparatus necessary is 

 a coffee cup in which to generate the gas. 



B. Strength of Oas and length of Fumi- 

 gation 



Numerous experiments have been made 

 to determine the effect, both upon the 

 aphids and the plants, of different 

 strengths of this gas and various lengths 

 of fumigation. Though these experi- 

 ments are not absolutely conclusive, they 

 seem to warrant the conclusion that in 

 a tight box or room, approximately 

 cubical in shape, gas at the strength of 

 three-tenths of a gram potassium cyanide 

 per cubic foot of space, fumigated for ten 

 minutes, or two-tenths of a gram for 15 

 or 20 minutes, will kill the aphids without 

 injury to the plants. These strengths 

 may safely be recommended for use. 



C. Procednre 



The process of fumigation is essentially 

 the same as that employed in fumigating 

 nursery trees. Earth is firmly packed 

 around the open bottom of the box. The 

 plants, which should be well cleaned of 

 earth, are laid on the trays, the bundles 

 being cut open and thoroughly loosened. 

 The lid of the box is then closed and 

 fastened. A coffee cup or similar vessel 

 is now placed in the lower corner of the 

 box by the door and into it is first 

 dropped a vial containing a proper 

 amount of the cyanide in solution. A 

 vial containing the sulphuric acid is then 

 dropped in and the door quickly closed. 

 Of course the vials are dropped in with 

 the mouths down, and if they be long and 

 narrow the contents will drain out gradu- 

 ally, avoiding a puff of the gas by too 

 rapid generation. The box is kept closed 

 for ten minutes, or as long as desired. 

 Both doors are then thrown open and the 

 trays lifted out so that the plants can be 

 thoroughly aired. 



The cyanide solution should be secured 

 from a druggist, put up in homeopathic 

 vials, one dose in each vial. The solu- 

 tion consists of 100 grams 98 per cent 

 potassium cyanide dissolved in water to 

 make c.c. solution. The amount neces- 

 sary for each dose is easily computed; 

 multiplying the cubic contents of the box 

 by four-tenths will give the number of 

 cubic centimeters of the solution to be 

 used (this giving a strength of two-tenths 

 gram potassium cyanide per cubic foot). 

 Use an equal amount of sulphuric acid, 

 which can be readily measured into emp- 

 ty vials. Thus for the box described, 

 2x2x2% feet, or 10 cubic feet, 4 c.c. of 

 the solution, or a two-drachm vial half 

 full, and an equal amount of sulphuric 

 acid (best grade commercial, 1.85 sp. gr.) 

 would be used for a strength of two-tenths 

 gram potassium cyanide per cubic foot, or 

 the same vial three-quarters full for a 

 strength of three-tenth gram potassium 

 cyanide per cubic foot. 



P. Caution 



Cyanide of potassium is as deadly a 

 poison as is known, and is sure and cer- 

 tain death if taken internally — no anti- 

 dote being know^n. Each vial should 

 therefore be plainly labeled in red, with 

 a druggist's poison label. 



The vials should be locked up, and af- 

 ter use should be carefully washed. The 

 residue left after the generation should 

 be washed from the vessel and buried so 

 that it cannot be found by animals. The 

 sulphuric acid should also be labeled and 

 carefully handled, as it will destroy cloth- 

 ing and other things with which it comes 

 in contact. 



3. Prevention of Introdnctlon of Aphis 

 After Planting 



With uninfested plants planted on clean 

 land there exists no chance for injury 

 from the root lice except by the winged 

 form being introduced from neighboring 

 beds. Thus in many cases it will be neces- 

 sary to plow under deeply the old infested 

 beds some time before the winged lice ap- 

 pear in order to prevent their spread to 

 the ones newly planted. 



