62 INSECT PESTS 



stalk with her sharp ovipositor and causes a swelling, 

 which increases in size as the larva grows, and it thus 

 obtains board and lodging combined. The period of 

 growth is about four weeks. 



Birds are the natural enemies of the Turnip Gall Weevil, 

 including the jackdaw, chaffinch, starhng and magpie, 

 which do good work in picking off the adult insects. In a 

 badly infested field however, whether it be cabbages or 

 turnips, the crop, which is not be-fouled so much as stunted 

 by their presence, should be consumed as soon as possible, 

 and stalks and waste should at once be burned. The 

 next crop should be grown as far as possible away from 

 the infested site. (See Plate 14b.) 



Cabbage Root Fly (C. brassica) is a more serious 

 matter. This is a dipterous greyish insect a Httle smaller 

 than a house-fly. The attack takes place when the plants 

 are quite young, just as we have flattered ourselves we 

 havd got rid of the club nuisance. The eggs are laid in 

 April and May just above the surface and for this reason 

 felt discs are good, placed around the roots and resting 

 on the soil. The maggots, being bUnd and weak, are 

 incapable of crawling over and under the disc to get at 

 their work, and so die. Carbolic acid emulsion as a soil 

 spray is also used. The natural enemies of the Cabbage 

 Root Fly in addition again to birds, are found among the 

 Rove Beetles, two or three kinds of which destroy this 

 insect. They are shining black in colour. A. fuscipes 

 is the largest of them. (See Plate 14a.) 



Aphides also attack cabbage. I shall have something 

 to say about them later. 



The Snowy Fly, or Cabbage Powdered Wing, is a 

 minute moth-like creature. Several are shown in the 

 sketch on the underside of the leaf, where they make their 

 appearance as white blight and their tiny larvae suck the 

 juices of the plant. The insect breeds in situ all the year, 

 principally in the summer, and can be prevented by the 

 use of the soap and quassia spray. Where it has gained 



