New York Agricultural Experiment Station. 417 



destructive to untreated cabbages, a large percentage of the plants 

 protected by card disks have produced marketable heads. This 

 method of protecting early cabbage is simple, and when compared 

 with the losses which some truck growers have sustained in certain 

 trucking sections it is, moreover, quite inexpensive. In addition to 

 actually reducing the number of plants killed by the insects another 

 important result of the experiments should be noted, that tar pads 

 have largely prevented root injury, which though not sufficient to 

 kill the plants may be extensive enough to retard growth and the 

 maturing of the cabbages, so that the crop fails to reach the earliest 

 market when usually the highest prices prevail. This is an impor- 

 tant consideration, which in the past has not been sufficiently 

 emphasized or really appreciated by most truckers. 



Comparative merits of carbolic-acid emulsion and tar pads. — The 

 chief merit of carbolic acid in controlling the cabbage maggot is 

 that it will kill the eggs and young larvae of the insect. The dis- 

 advantages attending the use of the emulsion are that several appli- 

 cations are usually necessary, the liquid must be applied in sufficient 

 quantities to penetrate the soil in order to reach the insects; and, 

 of most importance, that there is danger of injury to the tender 

 roots of the plant. Carbolic acid is a strong poison and our tests 

 as well as those of other workers have shown that even at the 

 dilutions used the roots of cabbages may be injured. A very serious 

 objection to this method of treatments is that in actual practice 

 truckers do not apply the emulsion until the injurious work of the 

 maggots is in an advanced stage and the plants are damaged beyond 

 recovery. The tar pads, on the other hand, can be applied immedi- 

 ately after the plants are set in the field and require no further 

 attention. They are safe, in that there is no possible chance of 

 injury to the plant by their use, and in our tests they have also 

 given efficient protection against the cabbage maggot. It has 

 proven much more easy to apply the tar pads than it is to make 

 a single treatment of the emulsion, for one man can carry to the field 

 enough tar pads to protect one thousand plants, while to treat 

 this number of cabbages with carbolic-acid emulsion would require 

 at least two and one-half barrels of the liquid. 



Cost of protecting cabbage with tar paper disks.— As to cost, the 

 single-ply tarred felt disks have in the past been offered for sale 

 at about seventy cents per thousand. In our experiments on sandy 

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