THE CABBAGE MAGGOT 25 



Reduced Dosage Treatments 



Corrosive sublimate solution 1-1920 has given good protection at a reasonably 

 low material cost. Two applications are nearly always advisable, and the 

 material must be applied very carefully. It is the most reliable of the reduced 

 dosage treatments and is highly recommended where a moderate or light infesta- 

 tion is expected. It can be used successfully in place of the standard corrosive 

 sublimate solution 1-1280 wherever the application is reasonably thorough. 



Calomel-talc dust 2 percent, mound method, has given good protection in the 

 two years that it has been used. However, there is evidence that it will be 

 satisfactory only if the dust is placed around the stem of each plant very care- 

 lully. The material cost is the lowest of all treatments. When applied by average 

 farm labor, the use of calomel-talc dust 4 percent will probably be more desirable. 



Calomel-talc dust 2 percent, duster method, was used only in 1942 and gave 

 only 54 percent protection. In spite of a very low material cost, the need for 

 three applications builds up a moderate labor cost. It is not recommended 

 unless calomel-talc dust 4 percent is unavailable. 



Calomel-talc dust 25 percent, pre-transplanting method, like the standard 

 pre-transplanting treatment, is limited in its use. In four years it has been only 

 slightly less effective than the 50 percent calomel-talc dust used in the same 

 way. The material cost and the labor cost are both very low, and where the 

 anticipated infestation is moderate or light it should be as satisfactory as the 

 stronger dust. 



Substitute Treatments 



Calomel-gum suspension 1-320 gave complete protection in 1940. However, 

 the material cost is extremely high and the preparation of a homemade suspen- 

 sion is too complicated for the average farmer. If a commercial preparation was 

 available at a reasonable cost, it would undoubtedly be a satisfactory substitute 

 for corrosive sublimate solution. 



Semesan suspension, when prepared by adding 3 ounces of Semesan to 10 

 gallons of water to provide a mercury content equal to the standard corrosive 

 sublimate solution, gave good protection in 1943. However, the cost is very 

 high and it is recommended only when other materials are unav^ailable. 



CABBAGE MAGGOT IN RADISHES 



Since the edible portion of radish, turnip, and kohlrabi is attacked, control of 

 the cabbage maggot in these vegetables must be perfect. In the experiments on 

 radishes at Waltham, complete protection was not secured and no practical 

 chemical treatment was discovered. The standard treatments with corrosive 

 sublimate solution and calomel-talc dust, which were used on cabbage, reduced 

 the injury to radish but permitted 20 to 50 percent of the plants to be infested 

 and caused some injury to the foliage and roots. Furthermore, these materials 

 are poisonous and treatment with them cannot be recommended freely because 

 the edible portion of the plant is exposed to the chemical. Rotenone dust was 

 not significantly effective. 



