42 THE REPORT OF THE No. 33 



ONION MAGGOT STUDIES IN THE DISTRICT OF MONTREAL, 



QUEBEC, 1923 



T. Armstrong, Entomological Branch, Dominion Department of 



Agriculture 



During recent years the market gardeners on the Island of Montreal have 

 suffered heavy losses in their onion crops due to the ravages of the onion maggot. 

 This year (1923) an effort has been made to study the life history and habits of 

 the insect and to determine an effective method of control. 



Dr. J. M. Swaine, 1 writing in the Second Annual Report of the Quebec 

 Society for the Protection of Plants, states that at Macdonald College, maggots 

 appeared last season (1909) for the first time and a number of plants were 

 destroyed. 



In the Montreal district serious losses were occasioned in 1920, and during 

 the past three years the successful growing of onions has been menaced by this 

 insect. 



Mr. Arthur Gibson, 2 in 1916-17, made use of a poison-bait spray consisting 

 of sodium arsenite, molasses, and boiling water, and apparently secured satis- 

 factory results. These experiments were conducted near Rivermead, Quebec, 

 and it was recommended that commercial growers test out the value of the 

 mixture under their immediate local conditions. 



In the United States, commencing with the year 1913, the use of sodium 

 arsenite as a bait received considerable attention, which resulted after several 

 years' experimentation, in the belief that the onion maggot could be successfully 

 controlled by poisoned attractive baits. 



In the spring of 1921, control work with sodium arsenite bait was carried 

 on in the Montreal district by Prof. W. Lochhead and Mr. W. J. Tawse, of Mac- 

 donald College, in co-operation with the Dominion Entomological Branch. A 

 number of fields were treated, making use of the two methods of application 

 which were being advised at that time, the use of bait pans, and the diagonal 

 sprinkling method. Fair control was secured according to the evidence pro- 

 duced by Messrs. Lochhead and Tawse, more especially with the use of the bait 

 pans. The sprinkling system proved to be unsatisfactory. 



Life History and Habits 



In 1923, at Montreal, the first onion maggot fly was noticed on the wing on 

 May 20, and ten days later, May 30, the first eggs were taken on a group of 

 volunteer onions. Flies continued to emerge throughout the month of June from 

 overwintering puparia. The maximum emergence occurred from June 10th to 

 13th, at which time from twenty to forty flies were seen to a pan and the greatest 

 numbers were taken sweeping. 



Eggs collected on May 30th hatched on June 5th, a period of six days. 

 These maggots reared in vials in the hollow of onion leaves commenced pupation 

 fourteen days later, with the majority going into the resting stage after sixteen 

 days. These puparfa gave rise to second-generation adults between July 4th 

 and 10th, the pupal stage lasting from fifteen to eighteen days. Oviposition of 

 the first generation was definitely in progress between May 30th and July 4th, 

 but continued in all probability at least until July 20th. Second-generation 



1 1909: Swaine, J. M.: Second Annual Report of the Quebec Society for the Protection of 

 Plants. P. 53. 



2 1917: Gibson, Arthur: Annual Report of the Entomological Society of Ontario. Pp. 30-33. 



