Reports to the Board of Agriculture. 17 



every year. The eggs laid iu the spring are placed on all kinds of 

 Cruciferaj ; the larvfe feed upon the leaves ; they are dull, smoky 

 yellow creatures, slightly hairy and spotted with l)lack, the liead and 

 the six legs are also black ; there is also a distinct caudal foot and a 

 row of tubercles along each side from which can be protruded curiou* 

 yellow glands ; when mature they reach al)out three-fourths of an 

 inch in length. These larvai can be easily seen on the leaves, and 

 are vulnerable at this stage. 



PrEYENTIYE and EEMEDIAL MeA8U1!ES. 



All precautions should be taken to destroy as much winter shelter 

 as possible. After a bad attack it would be advisable to burn the 

 mustard straw, not at once, but after it has been allowed to stand 

 some time in heaps in the fields ; the beetles would seek winter shelter 

 there, and on firing the heaps they would be destroyed. 



All hedge trimmings and reedy growths along dykes should be cut 

 and burnt during the winter. 



No experiments on a large scale seem to have been made in 

 destroying the larvaj upon the young plants when it is posdble to get 

 on the land. There is no doubt that the proper time to attack this 

 pest is in its larval stage when feeding upon the y<ning leaves. 



The fields should then be sprayed by means of a horse Strawsonizer 

 with Paris-green wash ; the time to carry out this operation would 

 depend upon the time the grubs are noticed on the leaves. 



The beetles also attack the young leaves, and would also be 

 destroyed by the same wash. The beetles may also be collected, when 

 present in numbers on the young plant, by dragging a long strip of 

 tarred sacking attached to a light rod over the fields, and also by 

 special machines. The beetles which attack the crop later on in the 

 year may be kept in hand by preventing their movements from place 

 to place. Towards the latter part of the year when so much damage 

 is reported, the l)eetles do not seem inclined to use their wings, but 

 migrate in a l)ody along the ground from field to field. Tliey can 

 thus be " held up " like locusts by cutting a trench across their line of 

 march, or by burning damp straw so that the smoke blows on to them. 

 The employment of a shallow trench about a foot deep is the best 

 plan to check them, especially if it can be filled or smeared repeatedly 

 with tar. 



It is also important to keep horse-hoeing as long as possible 

 between the rows ; by this means the pupa? are turned out of tlie 

 earth and are exposed to the attack of various birds. 



c 



