J. T. VVadsworth 83 



on infected roots, or preventing the deposition of eggs near the host 

 plants. With one or two exceptions, however, these remedies are of 

 httle practical value since they require, as a rule, frequent application 

 to the plants in order to obtain any satisfactory measure of success. 

 For this reason, and also on the score of expense, most growers are 

 averse to their use. Gibson and Treherne(t)), in their recently published 

 bulletin on the Cabbage-root Maggot, give a list of forty-eight 

 insecticidal mixtures or protective measures which they have experi- 

 mented with for several years. As a result of these experiments they 

 make the following statement : " It can be truly claimed that the only 

 protection to be relied upon for cabbages and cauUflowers and one 

 which is in every way practical, is in the use of tarred felt paper discs." 



The idea of placing paper collars round the stems of cabbage plants, 

 and thus preventing egg deposition in the soil near plants so protected, 

 originated with Prof. W. W. Tracy, of Detroit, Mich, in 1887. The 

 material (manilla paper) which he used, however, was unsuitable for the 

 purpose and the results of his experiments were unsatisfactory. In 

 1889 Prof. E. S. Goff of Wisconsin (7) substituted tarred paper for the 

 material used by Tracy, with complete success. Goff also devised an 

 efficient tool for cutting the discs expeditiously ; the latter were about 

 three inches in diameter, hexagonal in shape, with a slit extending from 

 one angle to the centre and with a star shaped cut also in the centre. 



Since GofE proved his method of protecting cabbages and cauliflowers 

 by means of tarred discs to be thoroughly practical it has been widely 

 adopted in America by commercial growers and others. The method 

 has also been tested at almost all the Agricultural Experiment Stations 

 in the United States and Canada in those districts where serious infesta- 

 tions of Cabbage- Maggots occur : \^dth one or two exceptions the resulting 

 reports have been entirely favourable. 



The fo]lo\ving authors have published reports of successful trials of 

 tarred felt discs: Slingerland(ii), Smith (12), Britton and Walden(3), 

 Caesar (4), Schoene{8 & 9), Britton and Lowry(2), Gibson and Treherne(6). 



On the other hand Schoyen(iO), Blair (i), and Washburn (15) obtained 

 unfavourable results in the trials which they made of tarred discs. 



In these cases the lack of success is attributed either to placing the 

 discs on the plants too late in the season, or carelessly, or to using tarred 

 paper — which curls — instead of tarred felt. 



The greater weight of opinion and evidence is distinctly in favour of 

 the tarred disc method of protection and the majority of the above 

 quoted observers agree that it is practical, economical and effective. 



