8 MASS. EXPERIMENT STATION BULLETIN 412 



Table 4. Date on Which the First Eggs of the Cabbage Maggot Were 

 Found at Waltham, Mass. 



The records shown in Table 4 are remarkably uniform for a thirteen-year 

 period, and seem to be a satisfactory index for timing control treatments in this 

 locality. 



If these dates are used for timing control treatments, the prevailing climatic 

 conditions in any particular locality should be compared to those at Waltham. 

 For example, observers in Bristol County (Massachusetts) have frequently 

 found the first eggs about five days earlier, and in northern Worcester County 

 (Massachusetts) seven to ten days later than they have been found at Waltham. 



Methods Used in Classifying Injury and Development of Head 

 in Cabbage and Cauliflower 



In the experiments reported in this bulletin, records of maggot injury and of 

 head development were taken from 1930 to 1934 by examining the head and 

 roots of each plant about ten weeks after it was transplanted. By this method 

 it was possible to determine the number of plants which were seriously injured 

 or killed by the cabbage maggot, but an accurate determination of slight or 

 moderate injury could not be made after the wounds had healed and the plant 

 had largely recovered. 



From 1935 to 1943 the plants were transplanted 18 inches apart in double 

 rows 18 inches wide. Each application of insecticide or other treatment was 

 made to two identical adjacent rows, one of which was used to record maggot 

 injury and the other to furnish data on the development of the head. Early in 

 June, about six weeks after transplanting and after the injury by the first genera- 

 tion of the cabbage maggot was nearly completed, the plants in one of each double 

 row were pulled and the roots carefully examined for injury (See Figure 4). The 

 injury was classified as: 



Slight — One or two maggots found, or evidence of feeding by not more 

 than two maggots; plant generally showed very little effect from injury 

 of this type. 



Moderate — Three or four maggots found, or evidence of feeding by 

 not more than four maggots; plant smaller than normal but probably 

 will recover and produce a small or medium-sized head. 



Severe — Five or more maggots found or feeding roots almost com- 

 pletely destroyed and main root stem badlj' injured; the plant will 

 probably die although occasionally it will recover and produce a small 

 and late-maturing head. 



Dead — Killed by maggot injury to the roots. 



