92 B.C. Entomological Society. 



to be attained was briefly to induce the female flies to feed upon the 

 poisoned liquid from the drops that fell either on the soil, or on the onion 

 foliage, or on the foliage of weeds and grass growing alongside the fields. 

 In this way the flies would be killed and the first generation of maggots 

 would be prevented. Later on, owing to the labour involved in this opera- 

 tion of spraying, ordinary pie-dishes were used at the rate of from twenty 

 to forty to the acre, with a quantity of the same poisoned liquid in each 

 dish. At the present time it is my understanding, although there are few 

 published records of the work, that both the spray method and the pie-dish 

 method are employed by onion-growers in Eastern Canada and Eastern 

 United States. 



In order to test the efficacy of the treatment in British Columbia, steps 

 were taken in 1918 and in 1919 to run a series of experiments. Since the 

 summer of 1914 the annual losses suffered by onion-growers through the 

 work of the onion-maggot have been gradually increasing in severity. In 

 the spring of 1918 several growers evinced the desire to take steps to effect 

 control. Unfortunately, the Entomological Branch, at this time, were 

 unable to undertake any definite control measures or to study the life-history 

 owing to pressure of other work. The growers were advised on the 

 method of using the sodium-arsenite and molasses bait. The pie-dish 

 method of using the bait was suggested, for the reason that it was felt 

 that the spreading of the bait in coarse drops of spray would not suit our 

 conditions in the Okanagan. 



Accordingly, two fairly large onion-growers set out twenty pie-dishes 

 to the acre, using the bait consisting of J4 oz. of sodium arsenite and ^-i 

 pint of molasses to a gallon of water, and starting them going about the end 

 of April. These pie-dishes were maintained during May and until June 

 14th, after which time they were allowed to dry for a month, being renewed 

 for a few weeks in July. On June 14th, at the suggestion of these growers, 

 an examination of the onion plantations was made, and advice was further 

 requested as to how to save the plantation which was severely injured by 

 maggots. Examination revealed the fact that the onions were heavily 

 infested despite the use of the baits over the period mentioned. The 

 growers had made an honest endeavour to retain moisture in the pie-dishes, 

 but it was a difficult matter owing to the rapid evaporation. Dishes filled 

 at noon were found to be absolutely dry by 3 o'clock in the afternoon. 

 Fresh water at the rate of 13^ pints to each dish was added daily, and once 

 a week a fresh solution of bait was made up and poured into the dishes. 

 Close examination of the fields on June 14th showed that very few 

 unhatched eggs were present and that few flies were in evidence flying over 

 the plantations. The onions had been thinned in May by hand, but despite 

 this fact it was evident that a heavy loss from the maggot was to be antici- 

 pated. Judging from the conditions, it would appear that the point of 

 heaviest infestation had been reached; it was therefore suggested that the 

 crop be rethinned and that all infested onions be pulled up and burnt. One 

 grower with 8 acres of onions arranged in two blocks. 5 and 3 acres each, 



