^62 AN ECONOMIC ENTOMOLOGY, 



l;irvae from gettinc^ at the desired point, since they seem to be 

 unable to live exposed to sunlight. Ground tobacco, kerosene 

 •ind sand, plaster, soot, ashes, and oilier materials placed at the 

 base of the plants act like the tarred pai)er as a mechanical pro- 

 tection, and must be applied before the eggs are laid, else they 

 will prove ineffective. Bisulphide of carbon injected below the 

 root system has been used with a considerable degree of success, 

 the fumes filtering through the soil and killing the insects at 

 work on the plant without injuring the plant itself An injector 

 devised for the especial purpose has been made by Mr. J. J. 

 McGowen, of Ithaca, New York, and perhaps the application of 

 this substance is the most certain and satisfactory remedy that 

 has been proposed.. It should be used when the soil is moist, 

 but not water-soaked. There are two or three broods in the 

 course of the year, according to latitude. The winter is passed 

 either as a pupa below the surface or as an adult in barns, 

 houses, etc., and the species is tided over between cultivated 

 crops by the cruciferous weeds. Hence clean culture and the 

 prompt removal of all crop remnants are urgently indicated. 

 Carbolic acid and kerosene, emulsified with soap according to the 

 formulas elsewhere given, have proved effective as killing agents 

 when the maggots have begun feeding. Pour about half a pint 

 around the base of the infested plant, diluting the carbolic acid 

 emulsion thirty times and the kerosene emulsion twelve times. 



Radishes frequently suffer from the attacks of the same 

 maggots, and they are more difficult to deal with here, because 

 they puncture the fleshy root and make channels through it in 

 every direction, safely beyond the reach of any insecticide appli- 

 cation. It rarely pays to put expensive substances on radishes, 

 because the margin of i)rofit is too small ; but considerable 

 benefit may be derived from proj^er methods of fertilizing, and 

 the mixture that seems to offer the best chance for success is 



Nitrate of soda 700 pounds. 



Ground rock 1000 pounds. 



Muriate of potash 300 pounds. 



Apply soon after the plants are up, or when the leaves are about 

 an inch long, at the rate of five hundred pounds per acre, and 

 before or during a rain. The application made at this time seems 



