278 W. L, WATERHOUSE. 



ON THE PRODUCTION IN AUSTRALIA OP THE 

 AEOIDIAL STAGE OF Puccinia graminis Pers. 



By W. L. Waterhouse, m.c, b.sc, Agr. (Syd.), d.i.c. (Lond.) 



With Plate XIX. 



[Read before the Royal Society of N. S. Wales, December?, 1921.~] 



Introduction. 



There are several kinds of rust which attack the cereals 

 and grasses, but in Australia the one which does most 

 damage is the black stem rust, Puccinia graminis Pers. 

 In some seasons the losses it causes to wheat-growers are 

 enormous. In 1916, the losses in the United States and 

 Canada were estimated at 280,000,000 bushels of wheat, or 

 one-third of the entire crop. (1) Indeed the ravages of the 

 rust have become so great in these countries as to consti- 

 tute, in parts, the limiting factor in wheat production. The 

 damage done in Australia is not so great. McAlpine (2) 

 states that the loss to Australia in 1889 was estimated at 

 between £2,000,000 and £3,000,000. More recent figures 

 concerning New South AVales are available. Mr. A. H. E. 

 McDonald, Chief Inspector of Agriculture, estimates that 

 in 1903 the losses in the North- Western and Northern Table- 

 land Districts reached 3,000,000 bushels valued at over 

 £400,000. In 1916 he estimates the losses in New South 

 Wales at £2,000,000. All these are losses occasioned in 

 "epidemic years" when the weather conditions are par- 

 ticularly favourable to the parasite. But in ordinary 

 seasons the rust is to be found in most districts, and is 

 probably responsible for a depleted grain yield of perhaps 

 five to ten per cent, of the crop. Such immense losses 

 have led to a very careful investigation of the fungus by 

 numerous workers. 



