178 



FRIT FLY {OSCINIS FRIT) IN RELATION TO 

 BLINDNESS IN OATS 



By A. ROEBUCK. 



(Lecturer in Agricultural Biology, Harper Adams Agricultural 

 . College, Newport, Salop.) 



(With Plate XII.) 



Introduction. 



The West Midlands, in common with many other areas in the country, 

 suffers severely from the terrible scourge Frit Fly, and every year 

 apparently one can find fields of oats ruined by its depredations. 



During extensive observations on frit flies and oat crops since 1913, 

 I have often noticed a considerable number of "blind" spikelets in the 

 panicles on infested fields. 



The continued association of these "blind" spikelets on attacked 

 crops, whereas good crops with little or no trace of the fly show no signs 

 of them, naturally suggests some connection, direct or indirect, with 

 Oscinis frit itself. 



The suggestion that the spring attack on the tillers so weakened the 

 plant as to render it incapable of nourishing all the flowers produced is 

 scarcely tenable. A comparison of oats with other members of the 

 Graminaceae would almost indicate that weakness in the plant would 

 show itself more particularly in the bottom or top spikelets, the middle 

 ones being usually well nourished, but "blindness" is found anywhere 

 on the panicle. 



Similarly in cases of severe grain attack to consider "blindness" due 

 to an early larva destroying the flower as soon as produced and finding 

 insufficient nourishment moving off to other flowers, is unconvincing. 

 The "blind" spikelets are already produced when the panicle unfurls 

 and therefore before the eggs can have been laid in the ears. Moreover, 

 careful examination of th€ behaviour of larvae in the grain attack 

 has not shown one case where the flowering glumes and palea are de- 

 stroved. 



