April, '15] 



BOURNE: OXION MAGGOT 



277 



either just breaking through the ground or were not yet in sight. The 

 field work, therefore, was begun much later than before and ran until 

 late in the summer. 



Upon frequent examinations, it was soon observed that the infesta- 

 tion was very slight compared with former years. Inquiry revealed 

 that this was noticed quite generally by onion growers in this region. 

 Along wdth this fact may be noted that two other very common pests, 

 the Colorado potato beetle and the squash bug, were also conspicuous 

 for their relative scarcity of numbers. Whether there was any direct 

 connection between the winter with its periods of severe cold, the late 

 spring season and this marked scarcity of these common pests which 

 normally occur in approximately the same relative abundance from 

 year to year, or whether it was mereh^ a curious coincidence, it is hard 

 to determine. 



The season's work was planned in general to follow out the lines 

 begun the previous year, to corroborate the results of that season's 

 work, and secure additional data as to details of manipulation of the 

 various materials used. 



Previous work had demonstrated clearly that remedies and methods 

 usually recommended for the control of the onion fly were out of the 

 question for use in large fields, both because of the initial cost of the 

 substances themselves, and the great expense for labor necessary to 

 prepare and apply them. Furthermore, most if not all of them de- 

 pended for the protection they gave, upon frequent renewals, all of 

 which made their expense mount up to a prohibitive figure. In fact, 

 their cost would often be higher than the loss caused by maggots, if 

 no treatment other than pulhng out infested plants during weeding 

 were given. 



Therefore some method of applying treatment at the same time, or 

 in connection with planting, seemed to offer the best chance of success. 

 This was taken up in 1913, as reported in the April number of the 

 Journal of Economic Entomology for 1914. The results of that 

 season demonstrated that several of the materials used were of so 

 little value that further work with them was impracticable. In this 

 class were naphthalene, soluble sulphur, powdered tansy, oil of tansy, 

 etc. Some of these were out of the question because of cost and diffi- 

 culty of securing in large quantities, and some had a decidedly injur- 

 ious effect upon the growth of the onion. This was true especially of 

 naphthalene. It appeared to control the maggots but at the same time 

 seemed to prevent germination to a large extent. Other substances 

 did not appear to have any effect upon either the plants or the maggots, 

 at least when used in quantities practicable from the standpoint of 

 expense. 



