1904.] 



The Hessian Fly. 



283 



Privy Council took special steps to ensure the wide distribution 

 of information respecting the pest, and of advice as to modes of 

 prevention and remedies. The weather of the two following 

 years, which was cold and wet, was unfavourable to the develop- 

 ment of the insect, and the infestation appears to have been 

 rapidly checked. 



The Hessian fly, a dark-coloured fly or midge, measuring only 

 one-eighth of an inch in length, lays its eggs in May and June 

 on wheat and barley, often just above the second joint or knot 

 on the stem, but sometimes lower down, or it may be a little 

 higher up. The legless maggots, which hatch in a few days, 

 live between the leaf sheath and the stem of the plant, and so 

 weaken the stem by their feeding that the stem becomes elbowed, 

 bending over just above the place of larval feeding. A month 

 or more, according to climatic conditions, may be passed in the 

 larval stage, and then pupation takes place under cover of a case 

 resembling in shape and size a small flax-seed. There may be 

 an issue of adult flies from these in the same year, but in Britain 

 the issue to be feared is that of the next year, at the end of April 

 or in May. The plants attacked include wheat, barley, and rye. 

 Couch grass and timothy are also subject to infestation, and the 

 possibility of these acting as breeding-places should be noted. 



When the crop is harvested, from the position of the infesta- 

 tion on the stem, many of the " flax-seed " or pupa cases will be 

 left in the stubble. Burning the stubble, or ploughing it in 

 so deeply that flies from the buried pupa cases will be unable 

 to reach the surface, should be carried out where practicable. 

 All screenings and " flax-seeds " that fall away in threshing should 

 be burnt. 



The grain of plants that have been attacked should not be 

 used for seed. The value of the grain depends to a great extent 

 on the reserve material passed into the seed during ripening, 

 and the plants stunted and weakened by attack will naturally 

 have poorer seed. 



Fertilisers, especially in the case of a mild infestation, would 

 prove useful in aiding the plant to tide over attack. Stout, 

 coarse-stemmed varieties of wheat and barley should be grown 

 as less likely to elbow. 



Clover following wheat is quite safe, as Hessian fly does not 



