69 



Another measure of prevention that should be adopted where hops are grown on a 

 large scale, is the removal and destruction of all wild or cultivated plum trees in the 

 immediate neighbourhood of the plantation. This will take away their winter refuge 

 from the insects, and save an infinite amount of trouble. 



"When the Aphis has made its appearance upon the hop vines, a kerosene emulsion 

 should be at once employed for its destruction. By careful watching and prompt treat- 

 ment this pest can, no doubt, be kept within bounds, but it must be dealt with without 

 delay, othewise its extreme prolificness will soon fill the hop-yard with myriads, and render 

 its destruction very laborious and difficult. 



The Onion Maggot (Phorbia ceparum, Meigen). 



This imported European insect is quite common in Canada and the Eastern United 

 States, and often proves very destructive to the onion crop. The attack is made by the 

 larva, or maggot, of a little two-winged fly, which eats into the bulb of the onion and 

 destroys it, partly by its own work, and partly by the decay which results from it. 



The accompanying illustration (Fig 40) represents the parent fly magnified, the line 

 below showing the natural size with outspread wings ; beneath this the pupa is shown, 

 and below it the maggot ; the figure to the 

 right exhibits the maggot devouring the interior 

 of the onion bulb. The fly lays her eggs early 

 in the season on the leaves of the young onion, 

 close to the surface of the ground ; from these 

 the young maggots are soon hatched, and pene- 

 trate downwards between the leaves to the base 

 of the bulb. Several of them are generally 

 found together ; they are yellowish white in 

 colour, tapering from one end to the other, and 

 destitute of legs. When not feeding they gen- 

 erally lie just outside the onion in a cell of wet 

 mud, which is kept damp by the exuding juice 

 of the injured plant ; they feed for about a 

 fortnight, and then transform in the earth into 

 brown pupae, of an oval shape ; from these the 

 flies emerge in a fortnight or three weeks, and 

 at once lay their eggs for a second brood. In this case, as the leaves are now high above 

 the bulb, the fly lays her eggs on the bulb itself, or on the ground close to it. At the 

 close of the season, the insect remains for the winter in the pupa state, from which the 

 winged flies come forth in early spring to begin another round of the life of the species. 

 Such, in brief, is the life-history of the insect. 



The best method of dealing with this insect is to prevent the attack if possible. Two 

 modes of doing this have been tried with success. The first, and most satisfactory plan, 

 is to bury the bulb of the onion so that the fly cannot deposit its eggs upon it. This is 

 done by earthing up the plants a3 is customary with potatoes and corn. The flies must 

 deposit their eggs somewhere, and prefer to do so on the bulb itself, or very close to it ; 

 if this is well covered up with earth the eggs are laid higher up on the plant, or on the 

 ground, and the young larvae, when hatched, are unable to get to their proper feeding 

 place, and consecpiently perish without doing any injury. Miss Ormerod recommends 

 growing onions in the garden in a trench, prepared in the same way as for celery, and 

 gradually drawing down the earth from the sides as the plants grow, thus keeping the 

 bulb always covered. She found this plan entirely successful in warding off the attacks 

 of the insect. 



The second mode of prevention is to scatter about the plants some substance that 

 will be sufficiently obnoxious to the female fly to keep her entirely away from the crop. 

 For this purpose gas-lime has been found most effective. It should be sown broadcast 

 over the bed about once a fortnight, but great care must be taken not to put it on too 

 thickly, as it is extremely caustic, and would seriously injure the plants. Mr. Fletcher 



Fig. 40. 



