REPORT OF THE ENTOMOLOGIST AND BOTANIST. 177 
- SESSIONAL PAPER No. 8a 
4. Traps.—During the cutting season the crop should be kept well down, a few 
shoots being left to attract the egg-laying females. In a week or so these should be 
cut and destroyed, other shoots being left to take their place. Young beds not old 
enough to be cut should be kept dusted with lime. 
5. Poultry.—Chickens and ducks when available are very useful in eating the 
beetles when they first appear in spring, and it is claimed they do no harm to the beds. 
THE BLACK VIOLET APHIS 
(Khopalosiphum viole, Pergande). 
Attack.—Dark coloured plant-lice clustering beneath and about the bases of the 
leaves and penetrating into the heart of violet plants grown under glass for winter 
flowering, sucking the plants and injuring them so as to prevent them from flowering, 
the growth being stunted and the leaves curled up. 
During the convention of the Canadian Horticultural Society held at Ottawa last 
September, Mr. J. H. Dunlop, a large florist of Toronto and an extensive grower of 
violets under glass, asked what could be done to prevent the attacks upon his violet 
plants by the Black Violet Aphis, which he stated had been a cause of considerable loss 
in his greenhouses. On October 13, a visit was made to Mr. Dunlop’s establishment 
by Mr. Arthur Gibson, of this Division, and specimens of the plant-louse mentioned 
were secured. These have since been bred in confinement, and specimens have 
been kindly identified by Mr. T. Pergande, through Dr. Howard’s courtesy, as 
Ehopalosiphum viole, a species lately described by Mr. Pergande. As a plant- 
louse, when examined closely, this is a very beautiful species, the body being of ‘a 
brownish green, marked with black patches, and the stigma and all the veins of the 
wings. are clearly and broadly marked with black. At the time of Mr. Gibson’s visit, 
the aphides were very numerous, almost every plant examined in most of the violet 
houses being found to be infested. Very little systematic work had been done at that 
time towards controlling these insects. Mr. Dunlop was of the opinion that, as is known 
to be the case, the violet is easily injured by tobacco fumigation ; consequently, 
little smoking had been done. Later, however, the attack became more serious and was 
the cause of a loss in this year’s violet crop, estimated at $1,000. Fumigation with 
tobacco had been resorted to for three weeks at intervals of one week apart, at the 
time of a second visit paid by Mr. Gibson on December 26. Powdered tobacco stems 
had also been dusted over some of the plants. These applications had killed many of 
the aphides, and the insects were then practically under control, but the plants were 
showing many spotted leaves, The treatment of violet plants with tobacco is considered 
objectionable by the best growers. Mr. B. T. Galloway, Chief of the United States Divi- 
sion of Vegetable Physiology, who has studied the commercial culture of violets and is the 
author of an excellent book upon that subject, writes as follows with regard to some 
leaves which were submitted to him from Mr. Dunlop’s houses where the fumigation 
had been done :—‘The violet leaves are affected with the well-known spot which is 
very apt to appear at almost any season of the year under certain conditions. In our 
experience we have never found it safe to use tobacco in any form on violets ; even the 
very weakest fumigations have a tendency to weaken the foliage and bring on spot. 
My suggestion in this case would be to thoroughly clean the plants, withhold water 
from the foliage for two or three weeks and keep a night temperature of about 40 
degrees, with a day temperature of 55 or 60 degrees. In other words, attempt to give 
as good conditions as possible to bring the plants to health.’ 
Remedies.—For greenhouse plant-lice and certain other insects, the most generally 
adopted methods to’ prevent such attacks is the fumigation with tobacco in its various 
forms. In the case of violets, however, as Mr. Galloway states, the tobacco fumigation 
tends to weaken the foliage and cause the ‘spot’ to appear. In an excellent bulletin 
recently issued by the United States Division of Entomology (Circular No. 37, 2nd 
8a—12 
