350 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



tor. Thus the whole life cycle from egg to adult requires about six 

 to ten or twelve weeks, according to the temperature and moisture, 

 and the second generation of flies appear in June in New Jersey or 

 by mid-July in southern Minnesota. The maggots of the second 

 generation seem to do but little damage. The life history of the 

 insect during late summer has not been satisfac- 

 torily determined, but there is undoubtedly a third 

 generation and in the South, possibly a fourth, the 

 work of the last generation being sometimes 

 noticed in late cabbage in early fall. On Long 

 Island, N. Y., the larvae have been observed as 

 abundant upon cabbage stumps in September and 

 October, working above ground, and the adults 

 and eggs have been common around the ad- 

 ventitious buds. Rough estimates indicate 300 

 to 1500 maggots per acre on these stumps. The 

 puparia of the last, and in the North possibly 

 some of those of the second generation, remain 

 in the soil over winter, though there is some evi- 

 dencethat the flies may also hibernate in the 

 Middle States. 



Control. The most effective measures of control consist in cul- 

 tural methods and preventives, but little practical success having 

 attended the use of remedies to kill the maggots. 



Cultural Methods. Inasmuch as the puparia remain in the soil 

 or in the old roots or stumps over winter, it is important for this as 

 well as other cabbage pests to gather and destroy all the refuse of the 

 crop as soon as possible and then plow infested land thoroughly in 

 the fall. Mr. Schoene has shown that by plowing badly infested 

 seed-beds six or seven inches deep that only one-fourth as many flies 

 emerged as where the soil was undisturbed. A rotation of the crop 

 will be of value where cabbages are not grown on large acreages. 

 Cabbage and other cruciferous crops should not be planted after 

 each other, as all are affected by the same pests. It is evident that 

 if the crop is planted at some distance from that of the previous 

 year, and as the flies are known to avoid wind-swept fields, 



FIG. 251. -Egg 

 of cabbage 

 maggot, 

 greatly en- 

 larged ; hair 

 line at center 

 of 6 shows 

 natural size; 

 b, outline of 

 side view. 

 (After Sling- 

 erland). 



