The Cabbage Root Maggot. 521 



I. EFFECTIVE METHODS. 



A. PREVENTIVE. 

 I. By Mechanical Devices. 



(a) Covered Frames over Plants. 



This method of growing the plants, either in a cold frame cov- 

 ered with cheese clolh or fine netting, or under a similar protec- 

 tion in the field, is of course, only practicable with small areas or 

 a few choice plants. Prof. Cook grew radishes successfally in this 

 manner in 1888. Wherever practicable it will prove a sure pre- 

 ventive, but must be applied early before the flies appear and be 

 kept on during nearly the whole season. 



(b) Tarred Paper Cards. 



This idea of preventing the attacks of the Cabbage Root Maggot by closely 

 encircling the stems of the plants by paper collars resting upon the ground, 

 first originated in Michigan in 1887. Prof. Tracy, of Detroit, experimented 

 with heavy nianilla paper, but n')t with satisfactory results. Prof. Cook also 

 experimented with the paper cards, and although he secured hundreds of 

 eggs where he used adhesive fly paper for the cards, yet he could not recom- 

 mend the method ; he seems not to have tested it again. 



In the spring of 1889, the idea occurred to Mr. GofF to substitute for the 

 manilla paper, cards made of tarred paper, and further protection was secured 

 by the use of a bit of grafting wax to form a more perfect union between the 

 paper and the stem. His experiment was a complete success. 



This preliminary experiment was so successful that the next season Mr. 

 Goff perfected the method by devising a very simple tool which would cut, 

 at a single operation, a six-sided card with a slit reaching to the center, and 

 with a star-shaped cut at the center, so that the same card may accommo- 

 date itself to any sized stem and still make a tight joint. He had these cards 

 tested bv several large cabbage growers that season. Mr. J. M. Smith, of 

 Green Bay, Wis., reported that he had about 7,000 plants protected with the 

 cards and secured a splendid crop ; while a like number of unprotected 

 plants nearby would have been an entire failure if he had not resorted to the 

 hand-picking of the maggots. Messrs. Smith Brothers of the same place also 

 reported a like success from the use of the cards. In 1891, these same par- 

 ties again used the cards. The former reported that he lost from the mag- 

 gots not more than 23 plants of the io,ooj to I5,odj that he protected with 



