INJURING THE ROOT. 189 



effect similar to that of the fungus causing the dis- 

 ease known as ' club-root.' In two or three weeks 

 the maggots become full-fed (a), and they change to 

 the pupa state within hard brown puparia (b), to 

 emerge some days afterward as adult flies. There 

 are probably three or four broods each season, and 

 the insect apparently hibernates in each of its three 

 later stages. These insects infest turnips and ruta- 

 bagas as well as cabbage, and some entomologists 

 consider the Radish Maggot as being also of this 

 species. 



Remedies. — Satisfactory remedies for this insect 

 are few and far between. European writers recom- 

 mend that coal dust be scattered around most of the 

 plants, leaving one occasionally without the dressing 

 to attract the flies to it for egg-deposition, and then 

 destroying the unprotected plants together with the 

 insects about their roots. Dr. Riley has suggested 

 that ashes or slaked lime will probably answer the 

 purpose as well as the coal dust. As some of the 

 larvae or pupae appear to pass the winter upon the 

 old roots, it is advisable to pull up and burn such 

 plants in autumn. Probably the most practicable 

 remedy is that of always putting new plantations of 

 cabbages some distance from where they were grown 

 the previous year. This has been found in practice 

 to give good results. The flies are sluggish, and 

 apparently do not scatter far from where they reach 

 maturity. The maggots may be destroyed by pour- 

 ing a small quantity of kerosene emulsion about the 



