Crop & Pest Report


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Hail Damage (07/04/19)

With warm and humid conditions, thunderstorms can develop and these storms may produce hail. Hail can potentially cause yield losses in many crops.

With warm and humid conditions, thunderstorms can develop and these storms may produce hail. Hail can potentially cause yield losses in many crops. Yield loss predictions are based on two factors: a) the growth stage at the time of damage and b) the degree of plant damage. In this article, I will focus on canola and soybean.



Before the bolting phase and flower development, canola can tolerate hail without much economic loss. Canola plants with leaves that are torn and shredded suffer only partial yield loss. Canola plants injured in late bolting or early flowering stages usually survive the injury. If the plant has a well-developed root system, it will have the ability to re-branch and develop secondary flower clusters. When buds or flowers are destroyed, the canola recovers rapidly by developing additional flowers, which normally would have aborted. New branches can also develop from growth buds lower down on the plant. Seed yield loss will depend on both the percent leaves and branches lost. If hail strikes late in the season, such as during pod filling or ripening, plant recovery is not possible. At the end to the season, the time needed to develop new growth, flowers, and pods is limited before a killing frost. Canola seed yield loss if injury occurs at the ripening stage, depends directly on the loss of branches, individual pods and seed loss due to shattering of mature pods.



Hail can potentially cause yield losses in soybean ranging from limited yield impact to total destruction of the crop. Plant damage may include leaf defoliation, stand reduction, stem damage and pod damage. The dominant growing point of the soybean plant is located near the top of the plant. However, there are also growing points in the leaf axils. If the top of the plant is damaged, regrowth can take place from one of more of the axillary buds.

Stand reduction is measured as the number of plants killed by the impact of the hail. Defoliation is calculated as a percentage of the leaf area destroyed. Leaf tissue that is green and still attached to the plant will continue the process of photosynthesis, and this tissue is not considered destroyed leaf area. Research has shown that leaf loss during the vegetative stages often has a limited effect on yield. Hail adjusters will estimate defoliation loss only in the reproductive stages. Most soybean plants will be in the reproductive stage in or following the second week in July.


Hans Kandel

Extension Agronomist Broadleaf Crops

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