140 DISEASES OF CROPS. 



The Cabbage Fly (Anthomyia brassicce) and The 

 Cabbage Root-eating Fly {Anthomyia radicum) belong 

 to the same genus as, and are somewliafc similar to, tlie 

 beet or mangel fly already described. The grubs of the 

 first-named insect injure the cabbage plants, " by eating 

 passages in the stem and roots, and sometimes destroying 

 whole fields of cabbages by subsequent disease, or decay 

 in wet weather, of the roots and lower part of the stalk." 

 The whitish grubs are devoid of legs, and measure about 

 one-third of an inch in length. The grubs turn to pupae 

 in the earth ; the latter are then transformed into perfect 

 insects in about twenty days, unless the pupae are formed 

 late in the season, in which case they hibernate until the 

 following spring. There are several generations during 

 the summer and autumn. The grubs of A. radicum are of 

 a yellowish colour, and feed in the roots of the cabbage 

 and other oleraceous plants. The perfect insect has a 

 slender, pointed abdomen. In this point it differs from 

 A. brassicce, which has a more or less rounded abdomen. 



Prevention. — (1) Rotation of crops. Farmers and mar- 

 ket gardeners should not grow cabbages on the same plots 

 of land season after season. (2) Dressing the land with 

 superphosphate of lime has been recommended as a means 

 of prevention. 



Cure. — (1) Lime-water is stated to destroy the maggots 

 of these two dipterous flies. (2) Lands previously infested 

 with these insects should be treated with gas-lime or 

 quick-lime. 



Clubbing in Cabbages {Plasmodiojphora brassica) 

 has already been described in chap. iii. Some agricul- 

 turists and entomologists still believe that clubbing in 

 cabbages and other brassicaceous plants is due to the 

 attacks of insects (!). This is a mistake, for true club- 



