16 



THE MILDEW OF CEREALS. 



G. Dimitriou, I.A.O., La Trappe. 



Introduction. 



Eeseareh such as the application of the most effective means of com- 

 batting the fungous diseases of our cultivated plants, demands a tliorougn 

 knowledge of these fungi. Indeed, if one maj' judge by what is actually 

 known regarding the phases of development of plant fungi, of their multi- 

 plication, of their mode of attack and of their resistance to all the 

 destructive agents, these circumstances vary so that general rules for their 

 destruction can be absolutely established only after a special study of the 

 life of each of these fungi. It is an indispensable condition for their 

 successful control. 



The united movement for the protection of plants against their natural 

 enemies, vegetable or animal, is of recent date in the Province of Quebec. 

 It can be largely attributed to the organization of the " Society for the 

 Protection of Plants," and to the continuous efforts of its President and 

 of his colleagues. 



Historical. 



In the experimental plots of the Agricultural Institute of Oka, set 

 apart for the acclimatization of certain varieties of wheat, a somewhat 

 sudden change became manifest at flowering time in the uniformity of the 

 green color of the lower leaves of the stems of this cereal. Soon this 

 change of color spread in all directions. 



Other varieties of wheat and rye growing alongside had a dusty 

 appearance. The change appeared to have reached its maximum inten- 

 sity after the rain on the 5th and 6th July. It showed itself principally 

 by secondary bushy tufts on the leaves, while the stems had not yet 

 appeared. A little later the disease invaded another part of the garden 

 containing selection plots of the two varieties, viz., rj^e — "Common." 

 "Ottawa select" and wheat — "Red Fife" and "Preston." The leaves 

 withered at a time when the plant had the greatest need for the elaboration 

 of food materials of the seed. The fungus appeared most vigorous on 

 the borders of the selection plots where the lower leaves presented the 

 worst appearance. It is to this white-ashy color of the leaf affected by 

 the fungus that it owes the name blanc des cereales (mildew of cereals) — 

 (Alphitomorpha communis — oidium monilioides — Erysiphe graminis). 



