g6 B.C. Entomological Society. 



conducted by the Professor and others in Wisconsin between 1913 to 1916. 

 The bait used was the Sanders formula, 5 grammes sodium arsenite dissolved 

 in I gallon of boiling water, to which is added ^ pint of molasses. This 

 bait was applied as a spray with a small compressed-air sprayer altered to 

 give a coarse spray, or might be applied by a whisk-broom, the operator 

 walking up and down the fields about every twelftli or fourteenth row and 

 releasing a quantity of spray at every four paces. In this manner about 3 

 gallons of the bait were applied to 7 acres about twice a week. The first 

 application was made as soon as the onions came up and were continued 

 until the later part of June. From the end of May the amount of spray 

 applications was doubled. From the end of June to the end of August a 

 series of fly-traps were used to test various modified baits. Of the baits 

 tried, the Sanders formula with the addition of sliced onions proved 300 

 times more attractive than other baits tested. A further experiment was 

 tried by distributing the bait in pie-tins at the rate of fifteen to twenty-five 

 tins per acre. The amount of success obtained with these baits in the field 

 did not come up to expectations, being attributed to continuous rains. 

 Mr. T. J. Headlee, of New Jersey, where similar tests had been made over 

 two years under drier conditions, states that very satisfactory results were 

 obtained. In the Okanagan Valley in the spring of 1918, owing to the 

 heavy loss in the onion-crop the previous year, a local grower was induced 

 to try the poison-bait method to protect his crop. He was instructed to 

 distribute tin pie-plates at the rate of twenty to the acre, and to prepare 

 the poison by dissolving 34 oz. of sodium arsenite in i gallon of boiling 

 water and to add to this J-^ pint of molasses. This bait was placed in the 

 plates and renewed weekly. Frequent visits were paid to this field to 

 observe results. Early in June it was found that, owing to our dry condi- 

 tions, the renewal of the bait once weekly was insufficient owing to the 

 rapid evaporation of the water, and dishes were found to be quite dry one 

 or two days after the bait had been placed in them; it was therefore found 

 necessary to renew the baits daily during the months of June and July. 



The adults of the onion-maggot were found to be attracted freely to 

 the bait when moist, but none were observed near dry or partly dry dishes. 

 Instead of renewing the bait daily, water was added to keep it moist, fresh 

 bait being only distributed weekly. The result was that considerable infes- 

 tation was noticed in the middle of June. It was then suggested that a 

 second thinning of the crop be undertaken and that infested onions be 

 removed and burned. Owing to the acreage under consideration and the 

 expense of a second thinning, also because there was considerable doubt 

 on the part of the grower as to the final results, the work was undertaken 

 on 5 acres of the crop which consisted of home-grown seed, and was more 

 vigorous than the balance of the crop which was sown to imported seed. 

 The work was carefully done and the poisoned bait continued ; by the middle 

 of July the rethinned onions were showing a perfect stand and the poisoned 

 bait was soon after discontinued. The harvested crop from the 5 acres of 



