Submitted by Anne Kirk, Cereal Crop Specialist, Manitoba Agriculture
Hail has been reported in several areas of Manitoba, and due to the size of the hail and duration of the storm, crops were affected in some areas. Assessments of damage will occur over the next few days. The amount of loss expected from a hail event depends on the severity of hail, crop type, and the growth stage of the crop.
Spring Wheat – is least susceptible to hail damage prior to stem elongation since the growing point is below the soil surface and will likely not be damaged. Hail damage during jointing or in the boot stage is difficult to assess. Spikes can still pollinate and fill, and regrowth from new tillers can occur. The more advanced the wheat is at the time of hail the greater the yield loss. The greatest yield reduction from hail occurs in the milk stage.
Oats and Barley – will tiller and recover better from hail than wheat, especially prior to the boot stage. Grower experience has demonstrated that barley hailed severely in the boot stage has recovered to produce 70-80% of normal yield. Crop hailed prior to the boot stage should be left if stems or green tissue remains.
Corn – early season hail occurring when the growing point is still below the soil surface will result in very little yield loss. At the 6 leaf stage the growing point is above ground, but leaf loss without damage to the growing point has a small impact on yield. Yield loss as a result of hail can be estimated by determining percent leaf defoliation (Table 2). Leaf area removed and leaf necrosis need to be considered, while damaged green leaf tissue should not be included. Assess leaves 7-10 days after a hail event, so that living and dead tissue can be easily distinguished.
Assessing Damage – New growth should be evident within a few days after a hail event. Assess crop to evaluate new crop growth. Yield potential of a damaged crop will depend on rainfall and temperatures in the next 30 days after hail damage.