pec. 1894.] 



INJURIOUS INSECTS AND FUNGI, 



199 



XIIL— INJURIOUS INSECTS AND FUNGI. 



Rust or Mildew on Wheat Plants. 



From many reports received by the Board of Agriculture 

 from various parts of the country it appears that rust or 

 mildew was by no means unusually prevalent on wheat plants 

 in the spring and summer of 1894, and, notwithstanding the 

 variable nature of the weather, exemplified by the abnormally 

 severe frost of May 21st, and the quantity of rain that fell 

 during the season in most districts, only a comparatively small 

 amount of injury was caused to the corn and straw by this 

 fungoid disorder. It will be remembered that in the Report on 

 Rust or Mildew on Wheat Plants (C. — 7018), published by the 

 Board in 1893, it was stated, as the opinion of many wheat 

 growers, that rust was always much worse in wet seasons and 

 when there had been late and severe spring frosts, like the 

 memorable frost of June 13th, 1892. But the experiences of 

 1894, coupled with the fact that, in foreign countries, where the 

 spring and summer seasons are hot and dry, rust is far more 

 harmful than in Great Britain, would seem to be antagonistic 

 to this theory. 



The fitfulness of the appearances of rust in this country may 

 possibly be the reason of the apparent indifference of wheat 

 growei's in respect of this fungoid disease. There would also 

 appear to be some misapprehension generally as to the amount 

 of actual injury caused by rust to the quantity and quality of 

 the corn and straw crop. It is very frequently not realised 

 that rust, in its yellow form at first, and later in the black 

 phase, upon the flag, stalk, and sheath of the wheat plant, 

 occasions serious harm. The fungus lives upon the host plant, 

 from which it absorbs the sap for its ov/n sustenance, thereby 

 cutting off supplies of food which should serve for the full 

 development of the grain. Besides, it chokes up the stomata, 

 hindering or preventing transpiration and respiration, and sets 

 up unhealthy conditions. Though it does not attack the grain 

 directly, the effect of its action upon the plants is to lessen the 

 number of grains formed, and in many cases to cause those 

 formed to be small, misshapen, shrivelled, and light. The straw, 

 also, is discoloured and rendered very brittle, and unfit for 

 anything but rough litter. 



It has been observed that rust is more frequently found upon 

 the flag than upon the sheathing leaves and the stems. This is 

 explained by the fact that the tissues of the flag are softer and 

 not so glaucous. The fungus also spreads to the ears both on 

 the outside and the inside of the glumes, but not to the grain. 



