21 



CROPS AX]> PESTS OX WHKH THE fiAS HAS 15KEX SUCCESSFTTLTA' USED. 



Fer7i.'i. — For Jhiral/id. moorcana infested with a scale insect {Chioiiaspis up.), 0.075 

 gram of 98 per cent potassium cyanide should he used for each cuhic foot of space 

 to he fumigated, not deducting the space occupied hy the plants. Length of expo- 

 sure, twenty minutes. 



One hundred and fifty to two hundred jylants with fronds in all stages of develop- 

 ment have been thus treated two or three times each year for the past four years 

 with no injury to the plants and almost complete destruction of the insect. They 

 were treated fifty at a time in a fumigating box (fig. 4.) , described later. 



Ad iantiim cuneatuvi and A. Bdll'd have been tried on a small scale and were not 

 injured l)y the treatment. 



Colcm. — ' ' Gol.len Bedder, " " Yerschaffeltii, " " Shylock, ' ' and others. 2-4,000 

 plants in pots, badly infested with the "white-tailed" mealy bug {Orthczia insigma) . 

 The house contained 15,587 cubic feet of si)ace. Treated at the rate of one-tenth of 

 a gram of 98 per cent cyanide of potasli per cubic foot of space for twenty minutes, 

 one hour after dark. Orthezia all killed and plants not injured in the least. All 



Fig. -J.— Fumigating box showing trays and coleus cuttings (from Woods and Jjoisctt). 



other means of destroying the Orthezia had been tried without effect. Large num- 

 bers of the common mealy bug were also killed by this treatment; but it was not 

 nearly so effective as for the "white-tailed" mealy bug. All coleus cuttings made 

 by the United States Propagating Gardens for the past two years have been fumi- 

 gated l)efore being prepared for the cutting bed (see fig. 4). 



Douhle English violets. — ' ' ]\Iarie Louise, " " Lady Campbell , ' ' and others. For plant- 

 lice and general fumigation fifteen-hundredths of a gram of 98 jier cent cyanide of 

 jwtash for each cul)ic foot of space is required. The exposure, if made according to 

 directions, will not hurt the plants in any stage of growth. The gas has been used 

 on a large scale in fumigating violets for the past three years with the greatest suc- 

 cess, only a few treatments during the season being required. Leaf-eating larvie, 

 slugs, millipedes, cutworms, etc., when exposed are killed as well as plant-lice. 

 Red spiders, however, are not entirely eradicated by the treatment. The foliage of 

 single violets like California and Princess of Wales are sometimes slightly injured 

 by the stronger dose of gas. A weaker dose (one-tenth of a gram potassium cyanide 

 per cul)ic foot) should be used when tliey are to be treated. 



