THE CABBAGE MAGGOT 23 



percent protection from commercial injury in 1943. In fact, the percentage of 

 salable heads where the greater dilution was applied was slightly greater in both 

 years. 



When calomel-talc dust was applied by the mound method, dusts containing 

 both 4 percent and 2 percent calomel gave 100 percent protection from com- 

 mercial injury in 1943 and were very effective in 1942. However, a slightK' 

 lower percentage of uninjured plants and salable heads in both years indicated 

 that the 2 percent calomel content was near the limit of practical effectiveness 

 and might give unsatisfactory protection with less careful application and less 

 favorable growing conditions. When applied by the duster method, dust con- 

 taining 2 percent calomel was definitely unsatisfactory in 1942. 



DISCUSSION OF CONTROL TREATMENTS 



The best treatment to use depends largely on the kind of equipment available, 

 the responsibility of the labor for making a thorough application, and the degree 

 of infestation. The most important factor is thoroughness of application, and 

 the most effective treatments will not gi^e satisfactory protection if they are 

 applied carelessly. This is especially true of those treatments where only one 

 application is recommended. A cost of ten dollars or less for the materials to 

 treat an acre of 12,000 plants is considered reasonable, and there is a distinct 

 advantage for the materials which require onl}' one application. 



Standard Treatments 



Corrosive sublimate solution 1-1280 gives very good control of heavy infesta- 

 tions when two applications are made at weekly intervals. In light infestations 

 one application is often satisfactory. Labor-saving equipment for applying is 

 extremely helpful, but even when applied by the bucket-dipper method it is 

 one of the most satisfactory treatments. 



Calomel-talc dust 4 percent applied by the mound method is very effective 

 and, since only one application is necessary, the material cost is slightly below 

 the average. However, the dust must be placed carefully around the stem of 

 each plant. W^here responsible labor is available, this treatment is among the 

 best. 



Calomel-talc dust 4 percent applied by the duster method has the lowest 

 material cost of any standard treatment and requires less than average labor per 

 application. Three applications are necessary to give effective control of a heavy 

 infestation, however, and the protection has not been consistently high. 



Calomel-talc dust 50 percent, pre-transplanting method, is particularly adapted 

 and recommended for use on plants which are transplanted with bare roots. 

 The over-all cost is reasonable and the results are good. It is highly recom- 

 mended for its special purpose. 



Tar paper discs are very effective when carefully applied. The cost is high 

 and careful application is slow and tiresome. They are very satisfactory for 

 use in small home gardens, and are particularly recommended for that purpose. 



