10 MASS. EXPERIMENT STATION BULLETir^J 412 



Seedbed Treatment 



In Massachusetts the earliest cruciferous crops are usually started under glass 

 and transplanted to the field before the first cabbage maggot infestation occurs 

 and, therefore, they do not need protection in the seedbed. However, many 

 cabbage, cauliflower, and related plants are growing in seedbeds between May 5 

 and May 30 or June 10 and July 1 when the flies are laying eggs and the young 

 plants are exposed to infestation. This is especially true of summer and fall 

 plantings which are seeded between May 15 and June 15. 



Corrosive sublimate solution is the most satisfactory material for seedbed 

 protection against the cabbage maggot as well as such diseases as club root, 

 blackleg, and damping-ofi". Clayton (4) recommends a 1-2000 solution (1 ounce 

 of corrosive sublimate dissolved in 15 gallons of water*) to control the common 

 diseases. Glasgow (5) recommends a 1-1280 dilution (1 ounce in 10 gallons of 

 water) to combat the cabbage maggot but shows that where the treatment was 

 carefully applied a 1-1920 dilution was practically as effective as the stronger 

 concentration. In fact, the actual increase in control from the stronger solution 

 was 1 percent or less. He also shows that the 1-1280 dilution was harmful to 

 cabbage and cauliflower seedlings growing in dry, sandy soil. 



No definite experiments to control cabbage maggot in the seedbed have been 

 made at Waltham, but in view of the above reports from New York as well as 

 the results of dosage experiments shown in Table 12 the recommendations for 

 seedbed treatment are: 



Apply corrosive sublimate solution, prepared by dissolving 1 ounce of corrosive 

 sublimate in 15 gallons of water (1-1920), using 1 gallon of the solution on about 

 40 feet of row or 20 square feet of bed. Applications should be made first as soon 

 as the flies appear or at the beginning of one of the fly periods and repeated three 

 or four times at weekly intervals. 



Where corrosive sublimate is not available or its use is undesirable for any 

 reason, a cheesecloth screen which tightly covers the coldframe or the seedbed will 

 effectively protect the seedlings during the critical fly periods. 



In New York (6) a calomel-gum suspension, which is described on page 18, 

 is recommended, but this treatment has not been used on the seedbed at Waltham. 



Pre-Transplanting Treatments 



In some sections, particularly on Long Island, N. Y., seedlings are protected 

 from cabbage maggot by coating the stem and upper part of the root with calo- 

 mel, either as a powder or as a liquid suspension (2), just before they are trans- 

 planted to the field. 



Experiments with this method were made at Waltham from 1935 to 1940 as 

 shown in Table 6. Dusts containing equal parts of powdered calomel and clay 

 or talc and 1 part of calomel with 3 parts of clay or talc were the most satisfactory 

 and consistently provided 75 to 85 percent commercial protection and produced 

 70 to 80 percent salable heads. The best control (about 95 percent) was obtained 

 from pure powdered calomel alone and from a mixture containing 3 parts of 

 calomel and 1 part of diluent, but these treatments occasionally injured the roots 

 and checked the growth of the plants. Dusts containing less than 20 percent 



*Actually 1 ounce in 15 gallons is a dilution of 1 to 1920. 



