TURNIP AND CABBAGE GNAT MIDGE. 183 



are some that might be worth trying. The larvae are very small and 

 tender, and as in the case of the very nearly-allied Cecid of the Pear, 

 Diplosis pyrivora, dressings of kainite sprinkled on ground where the 

 larvae have gone down have been found to act extremely well in 

 destroying a very large proportion of the grubs before their change to 

 the pupal state, there does not seem to be any reason why a dressing 

 applied when the maggots are leaving the pods might not answer 

 equally well in checking the Turnip as the Pear-blossom Gnat Midge.* 



It should also be noticed that there is a second brood of Gnat 

 Midges, which breed in the pods at the end of the shoots. It may 

 certainly be considered that the first infestation of each year arises 

 from the C. brassiccB which have wintered from the last brood of the 

 preceding season, probably in larval or pupal condition. 



This point is what we need especially to lay our hands on for preventive 

 treatment. Cutting off and destroying these small ends of shoots with 

 the small pods would pay well by checking coming infestation if attack 

 was found present. Also, from careful observation, such as that of 

 Mr. Sim, we might learn in what state the pests pass the winter, and 

 thus know with certainty whether they could be dealt with by dressings 

 or other agricultural treatment in the ground to which the larvae 

 dropped from the pods. 



* Beference to this application will be found under the head of Pear Gnat 

 Midge, p. 91, preceding, with mention also of other dressings effective in prevent- 

 ing development of larvffi. 



