1922.] 



The Control ok Maggots. 



281 



amounts of creosote and chalk. A quarter of an ounce of creosote 

 to 12 oz. of chalk gives the correct proportion, and in recent 

 trials it was found that 21 lb. of the mixture was sufficient for 

 each square rod (or, say, 80 square yards). To mix the two 

 together, the chalk can be put into a tin bath or similar recep- 

 tacle and the creosote added slowly, the chalk being continuously 

 stirred. The mixture should be applied in spring after 

 the plants are set out, being dusted round the seedlings 

 by using either a powder sprayer or a strong paper bag with a 

 hole in one corner. Two or three applications should be given 

 at fortnightly intervals. 



A third method of control, which has given good results in 

 America is treatment with corrosive sublimate. A solution of 

 1 oz. in 10 gal. of water should be made, and as the sublimate 

 requires a little heat to make it dissolve, it should be dissolved 

 first in a small quantity of hot water and then made up to ten 

 gallons. As it is poisonous it should be used with care. About 

 a tea-cup-full should be applied to each plant as soon as the 

 plants are set out, and four applications given at intervals of a 

 week or ten days. 



Onion Fly. — The onion fly (Hylemyia antiqua), like the 

 cabbage root fly, usually lays its eggs upon the plant and not in 

 the soil. Any chemicals used as insecticides against this fly 

 should be in the nature of deterrents to keep the fly away and 

 prevent it laying its eggs, as once the maggots have got into 

 the bulb of the onion it is too late to eradicate them. No such 

 mechanical device as the tarred felt disc is practicable, how- 

 ever, and we must look to other measures for its control. 



Experiments have been made with varying success. The 

 worst damage is done when the onions are in the seedling 

 stage, as the maggots -are capable of killing several onions by 

 migrating from plant to plant. Any insecticide must there- 

 fore be applied in early spring soon after the onions appear 

 above the ground. It is recommended that the fields 

 be dusted in early spring, when the onions are two inches long, 

 with a mixture of dry earth or precipitated chalk and green tar 

 oil, in the proportions of one part by weight of oil to ninety- 

 nine parts of chalk or dry earth (say J oz. to every 1J lb. chalk . 

 Several applications should be given at intervals of a fortnight. 

 The materials may be mixed and applied in the same manner 

 as for cabbage root maggot. 



The corrosive sublimate solution used against the cabbage 

 root maggot is well worth trying in this case also. Soot, which 



