Later, this fungal growth becomes dotted with black pepper-like sexual bodies that enable the fungus to survive between growing seasons. Damage occurs from reduced photosynthetic ability when green surfaces are shaded and the host is robbed of moisture and food by fungal growth. Yields may be reduced by 20 per cent or more. Cereals affected by mildew produce fewer tillers and grains per head and the grains may be poorly filled. Barley and spring wheat, other than soft white wheat, are seldom affected at economic levels on the prairies.
Winter wheat is affected to a greater degree.
Considerable losses have occurred in some seasons on soft white wheat. The disease will seriously reduce yields if the flag and second leaf are affected. Assess no less than 25 main tillers selected at random along two diagonals from one corner to the opposite corner of the field. Assess the percentage of first and second leaves affected. Take the average of the first leaf and the second leaf and apply it to the following formula.