The Cabbage Root Maggot. 553 



emulsion again. Had he made it according to his first formula and used it 

 more freely, we believe he would have had greater success in 1886. 



For, this is the experience of others who have tried the emulsion. During 

 the summer of 1887, Mr. Fletcher used Prof. Cook's first formula, diluting it 

 56 times, on radishes. He began 2 days after the seed was sown and treated 

 the bed, using an ordinary sprinkler, once a week until the radishes were fit 

 for the table. He grew radishes in this way all summer free from attack, 

 with no injury to the tenderest foliage nor was any offensive taste given to 

 the vegetable. 



This emulsion was selected as one of the preventives to be used on the 

 cabbages in our experiment on Long Island. Our emulsion was made by 

 dissolving i lb. of soap in >^ gal. of water and emulsifying this with i pint 

 of crude carbolic acid. Each cupful of this was diluted with 50 cupfuls of 

 water before applying ; thus about 38 gallons of the dilution would contain i 

 pint of the acid, or the emulsion was used about 3 times as strong as Prof. 

 Cook first used it. Our experiment was planned as described in the diagram 

 on page 551. Two half rows were treated with the emulsion, or about 300 

 plants in all. About ^ teacupful of the dilution was poured in a solid 

 stream from an ordinary sprinkler around the base of each plant. The first 

 application was made April 19, the day after the plants were set. A second 

 application was made by Mr. Reeve on April 30. On May 21, when we ex- 

 amined the plants, the maggots had done their worst, and in the untreated rows 

 there were scarcely 50 plants yet standing in either row. While about ^ of 

 those treated with the emulsion were in good condition and but few of them 

 had any maggots at the roots. In August, Mr. Reeve reported that he had 

 cut 90 heads from the west half of the fifth row and 85 heads from the east 

 half of the third row; while from the un reated rows he got only 90 heads 

 from the 600 plants set. Thus the results were quite encouraging. 



However, we doubt ifthe emulsion applied early in the season, acts to prevent 

 the flies from laying their eggs. Our experiments, recorded on page 529, 

 indicate that it is a powerful killing agent, and there is yet no definite evi- 

 dence that smells of any kind will keep the flies away. The discussion of the 

 emulsion as a killing agent on page 529 should be read in connection with 

 this account. 



Carbolic Acid and Plaster. — In 1888, Prof. Cook mixed the crude acid 

 with plaster (i pint to 100 pounds of plaster), and applied it around the stem 

 of cabbage plants. "None of the cabbages were attacked, but the slaking 

 or setting of the plaster about the plants was a serious injury to some of the 

 plants." Therefore, he could not advise its use for this purpose. 



B. DESTRUCTIVE. 



I. Destruction of the Maggots. 



{a) By Destroying Infested Plants. 



In 1833, Bouch6 concluded that the only way to diminish this destructive 

 fly is to pull up and destroy the infected plants with their accompanying 



