With the rainfall last week, came hail to a number of areas (Dauphin, Treherne and Notre Dame, MB; Duck Lake, Frontier, SK; Claresholm, Spirit River, AB). Hail stones were large in some areas (golf ball size at Frontier, SK) and fell for a significant period of time (hail fell at supper time at Claresholm, AB and hail stones were still present on the ground at noon the next day). Obviously hail damage in these situations is expected to be significant. In other areas, smaller hail stones for a brief period of time will result in much less crop damage. A well established root system and the ability to develop secondary flower clusters will help the plants recover. At the rosette stage, yield loss will be mainly related to lost leaf area. A general rule of thumb is that lost yield will equal about a quarter of the percentage of leaf area lost. When buds and flowers are lost due to injury, the plant recovers rapidly by the development of flowers that normally would have been aborted. The plant also develops flowering branches from growth buds lower down on the plant, replacing to a degree, the lost buds, flowers and pods. However, one concern this year will be the additional delay in maturity until plants recover. There are reports that some crops received 100% damage. If crops have been totally destroyed, there may still be time to seed green feed and qualify for crop insurance. Consult your local insurance agency for more information.
The following link has good information on assessing hail damage on canola: http://www.canolacouncil.org/contents5.aspx