THE CABBAGE MAGGOT 



17 



Table 10. Relation of Time and Number of Applications of 



4 percent Calomel Dust by the Duster Method for Control 



OF the Cabbage Maggot. Waltham, Massachusetts. 



Percent of Plants Commercially Injured 



Number of Applications — 



and Light Infestation Heavy Infestation 



Period When Applied* • • 



1933 1940 Average 1934 1935 1942 Average 



One application 



1st 4.0 4.0 56 62 59 



2d 7.0 7.0 48 44 46 



3d 90 70 80 



4th 80 86 83 



Two applications 



1st and 2d 3.0 3.0 18 24 7 16.3 



1st and 3d 30 34 32 



1st and 4th 60 30 45 



2d and 3d 44 46 45 



2d and 4th 60 60 



3d and 4th 68 82 75 



Three applications 



1st, 2d, and 3d 2.0 2.0 28 28 



1st, 2d, and 4th 28 28 



2d, 3d, and 4th 86 86 



Four applications 



1st, 2d, 3d, and 4th. . . 2.0 2.0 28 28 



None (Check) 57.0 68.0 62.5 86 99 88 91 



Period when applied: 



1st — On day when eggs were first found 

 2d — 1 week after first application 

 3d — 2 weeks after first application 

 4th — 3 weeks after first application 



Mound Method of Application. — Since 1941 calomel dust has been applied 

 in the experimental field at Waltham by placing a mound of the dust, equal to 

 the amount held in a teaspoon, around the stem of each plant soon after trans- 

 planting or just before the active period of the flies. As shown in Tables 9 and 

 12, this treatment has consistently given excellent control, being completely 

 effective in some experiments, and in many respects it has been the most satis- 

 factory method used. 



The mound method was first suggested to the writer by Neely Turner of the 

 Connecticut Agricultural Experiment Station. At Waltham, a teaspoon has 

 been used to dip the dust from a bucket and place it around the stem of the 

 plant, but with a little care the dust can be "squeezed" from the hand to make a 

 satisfactory application. This method requires considerable hand labor and no 

 satisfactory equipment for mechanical application has been discovered. How- 

 ever, one application is sufficient and the labor for applying is no greater than 

 that required for other effective methods of hand application. Calomel is an 

 internal poison and when applied by hand reasonable precautions should be 

 observed. 



Dusts containing 4 percent and 2 percent calomel combined with talc or clay 

 have both been used successfully and the concentration is discussed on page 22. 

 If carefully applied, 100 pounds of dust will treat about 1 acre of plants. 



