234 VEGETABLE FOES AND DISEASES 



4. When Onion plants in a garden or field are 

 noticed to droop and wither all such plants should be 

 taken up and burnt. If taken up with a small three- 

 pronged fork, the maggots will usually be removed 

 with the plant. If this is done early all the larvae will 

 be got rid of, but if deferred they will have left the 

 bulb and have turned into pupae in the soil. 



5. All pieces of bulbs should be removed from in- 

 fected land as pupae sometimes remain in the bulbs, after- 

 wards dressing with gas lime, two and a half to five tons 

 per acre. After spreading evenly and leaving a month 

 or six weeks plough deeply or trench the ground. 



6. Wherever possible, Onions should not be grown 

 again for at least one season on land where the crop 

 has been infected, as the pupae remain in the ground 

 during the winter. 



THE ILLUSTRATIONS REPRESENT ONION FLY : ATTACK AND EFFECT 

 ON ONIONS. 



A, Onion Fly : a, natural size ; b, enlarged three diameters. B, 

 larva, commonly called maggot : c, natural size ; </, magnified 

 three times. C, pupa, sometimes called fly-case : e, natural 

 size ; f, enlarged three diameters. D, young Onion at usual 

 earliest stage of attack : g, eggs of Onion Fly deposited on 

 leaf bases ; h, eggs deposited on ground close to bulb. E, 

 attack on plant after bulb commenced forming : j, eggs laid 

 in leaf axils ; j 9 dotted line indicating course taken by maggot 

 after hatching out to base of bulb ; k, hole eaten by maggot in 

 passing into bulb. F, section of Onion infested with maggot : 

 /, hole made by larva or maggot in entering bulb ; m, burrow 

 in bulb with maggot lying in it. G, Onion destroyed by 

 Onion Fly : n, top withered ; o, centre of bulb decayed with 

 maggots in it. 



