An Overview of Hail Injury and Fungicide Use on Soybean

Farmers and agronomists often consider applying a fungicide after a hail event because of plant health claims on many fungicide labels and the natural tendency to take corrective action after a storm (Figure 1). This publication provides research-based guidance to evaluate the benefits of this practice and support profitable management decisions.

It is important to distinguish between crop injury and crop damage. Crop injury refers to any unhealthy alteration of plant tissue, growth, or function, whereas crop damage is the resulting economic loss, impact on quality, or yield reduction. Injury from hail, or any other stress, does not necessarily lead to yield or quality losses.

Crop response to hail injury varies depending on the soybean growth stage, the severity of injury, and the environmental conditions surrounding the hail event. For example, minor hail injury during vegetative growth stages is unlikely to reduce soybean yield. In fact, soybeans can tolerate substantial defoliation during vegetative growth with relatively little impact on yield (Table 1). However, soybean seedlings are particularly vulnerable to stand loss when stems are broken below the cotyledons or the first node, as these plants have limited ability to recover.

For more information on how to determine soybean growth stages and soybean physiology, see Crop Scouting Basics for Corn and Soybean: Soybean Growth Stages.

Table 1. Estimated indeterminate soybean yield losses from hail at various growth stages. Adapted from the 2026 USDA FCIC Soybean Loss Adjustment Standards Handbook.

Soybean is injured by hail in several ways. Leaves may be tattered or knocked off the plant by hail, reducing photosynthetic capability (Figure 2). Stems can be bruised, broken, or removed, resulting in stand loss. Hail can injure developing pods, cause seed abortion, or knock pods off the plant, directly reducing yield and grain quality (Figure 3). Field areas where the crop canopy is thinned, or stands have been reduced, may be more susceptible to weed infestations. Although hail injury often appears severe after a storm, soybean plants have a remarkable ability to recover. Soybean plants have multiple growing points (meristems), allowing for rapid regrowth and plant recovery following injury, provided stems have not been cut below the first node.

One of the primary reasons that farmers and agronomists consider fungicide use after a hail event in soybean is the perceived potential for infection by pathogens that cause disease. Bacteria, for instance, do not require wounds to enter a plant, but are certainly aided by wounds. However, fungicides are ineffective for managing diseases caused by bacteria. Fungi do not require wounds to enter a plant. Although abiotic stress can weaken plant defenses, in some cases, abiotic stress can boost immunological responses.

Another reason fungicides are considered after hail injury has to do with preserving or recovering plant health. Certain fungicide labels report physiological responses that improve plant health and reduce abiotic stress. The ultimate goal of a fungicide application is to protect a crop, maintain yield potential, and maximize farm profitability. This most often means more bushels at harvest, but it can also mean improved harvestability (standability). A hail-injured crop can have a reduced yield potential, meaning there is less yield potential that can be preserved by a fungicide.

Despite the potential for fungal infection through wounding and the reported plant health benefits of certain fungicides, research from land-grant universities, and other sources indicates that fungicide use after hail injury on soybean is unlikely to provide a consistent return on investment. If the fungicide application is not likely to be profitable, it should not occur. Beyond decreasing profits, unnecessary fungicide applications can also increase the risk of fungicide resistance development.

Example Hail Research Results

• Scientists at Iowa State University simulated hail at approximately R1 and R4 in soybean. Fungicide alone, insecticide alone, and fungicide+insecticide treatments were applied at approximately R3. Data indicated that these pesticides did little to preserve yield in hail injured soybean in low-disease risk environments. Only 29% of the plots receiving an R3 fungicide after an R1 hail event had a positive economic return. When fungicide was applied at R3 and hail occurred at R4, 42% of the plots had a positive economic return.

• Researchers from the University of Wisconsin-Madison applied a fungicide to soybean (R3 growth stage) 12 days after hail injury. The fungicide application provided no yield benefit over the nontreated plots.

Early Season Hail

Vegetative stage soybean plants are the least susceptible to hail injury from defoliation, In fact, the USDA Soybean Loss Adjustment Standards Handbook estimates there will be no yield losses for indeterminate vegetative stage soybeans at any level of defoliation. However, determinate soybeans in the vegetative stages are more susceptible to defoliation than indeterminate soybeans. Soybean seedlings can be at particular risk for stand loss due to the potential for stem breakage below the first node. If stems break below the first node, the plant cannot regrow. Beyond stand reduction and defoliation, early-season hail can cut nodes from the plant and injure stems (Figure 4). Injured stems have increased stem rot susceptibility and can lodge, leading to harvest issues.

If replanting is required, follow the guidelines recommended by your state Extension soybean agronomist. These recommendations often include a waiting period, which is necessary to evaluate which plants will have active regrowth. The best option will change depending on multiple factors. Consider how lateseason planting can reduce soybean yield potential and the cost of replanting. It may be more cost-effective to keep an existing low population than to replant at a higher population due to seed, fuel, labor, and machinery costs, coupled with a lower yield potential due to late planting. Soybean plants are capable of compensating for certain levels of reduced stand as they can branch out to fill voids. Additionally, evaluate stand uniformity; uniformly low stand count fields will perform better than those with large gaps in the stand. More information on assessing plant stands to determine if replanting is necessary can be found in the factsheet Soybean Plant Stands: Is Replanting Necessary from Science for Success.

Mid and Late Season Hail

Soybean is most susceptible to hail injury during the later reproductive (R) growth stages as the plant's ability to compensate for damage decreases. Hail can cause defoliation, break and bruise stems, and injure pods. Defoliation reduces photosynthetic capacity, while broken stems destroy entire portions of the plant. If hail injures developing pods, there can be grain quality issues, seed germination in the pod, and direct yield loss (Figure 5). When pod damage is prevalent, prioritize affected fields for early harvest to minimize harvest issues such as lodging, reduced seed quality, green stem, seed diseases, etc.

Other considerations for hail-injured soybean

• Before any management decisions are made, contact your crop insurance agent to get an assessment. Failure to do so may void your policy.

• Weed seeds may germinate if the soybean canopy is destroyed by hail, increasing the risk of weed competition and seed bank additions. If herbicides are used, pay attention to pre-harvest intervals, rotation restrictions, and crop injury potential.

• Applications of foliar fungicides may lead to increased incidence of green stem that may decrease harvest efficiency.

• Grain moisture content may be impacted. Research found higher harvest grain moisture when soybean was injured by simulated hail at R1 than in non-injured plots. However, simulated hail at R4 did not result in higher grain moisture compared to non-injured plots.

How to avoid additional economic loss after hail injury on soybeans

• Do not make immediate decisions about a hail-injured crop unless it is certain that the field will not recover. Situations where recovery is not possible include stem breakage below the first node on most plants throughout a field or destruction of mature pods.

• Understand your crop insurance coverage policy. Avoid investing additional inputs in a field where the economic impact of the damage cannot be recovered.

• Research indicates that fungicide application to hail-injured soybeans is unlikely to improve yield. Fungicides are most profitable when disease risk is high. Management decisions should be based on expected disease risk (field history, weather forecasts, growth stage, etc.) and economic return rather than on hail damage alone.

• Do not apply a half-rate of fungicide to hail-injured crops. Reduced rates can increase the risk of fungicide resistance development. If a fungicide application is made, use a labelled rate to avoid future plant disease issues. A half-rate may save some money, but the cost and time required to apply the fungicide are the same as a full-rate application. The level of potential disease control may be substantially reduced!

References

Conley, S.P., Esker, P., and Gaska, J. 2010. Use of Fungicides in Hail-Damaged Crops. Proceedings of the 2010 Wisconsin Crop Management Conference. Vol. 29. Article

Sisson, A.J., Kandel, Y.R., Hart, C.E., Asmus, A., Wiggs, S.N., and Mueller, D.S. 2016. Effect of foliar fungicide and insecticide on hail-damaged soybean. Plant Health Progress 17:141-148. Article

Acknowledgements

Authors

Dylan Mangel, University of Nebraska-Lincoln; Martin Chilvers, Michigan State University; Albert Tenuta, Ontario Ministry of Agriculture, Food and Agribusiness; Daren Mueller, Iowa State University; Adam Sisson, Iowa State University; and Shawn Conley, University of Wisconsin-Madison.

Reviewers

Travis Faske, University of Arkansas; David Hooker, University of Guelph; Heather Kelly, University of Tennessee; Dean Malvick, University of Minnesota; Trey Price, LSU AgCenter; Damon Smith, University of Wisconsin-Madison; Terry Spurlock, University of Arkansas; and Richard Wade Webster, North Dakota State University.

Sponsors

The authors thank the United Soybean Board and the United States Department of Agriculture - National Institute of Food and Agriculture for their support.

Artificial intelligence was used to rewrite human-generated text for portions of this publication. AI-generated content was carefully reviewed and verified by the authors.

Citation suggestion: Mangel, D., Chilvers, M., Tenuta, A., Mueller, D., Sisson, A., Conley, S. 2026. An Overview of Hail Injury and Fungicide Use on Soybean. Crop Protection Network. CPN-4015. https://cropprotectionnetwork.org/publications/an-overview-of-hail-injury-and-fungicide-use-on-soybean.