David Moseley and Boyd Padgett, LSU AgCenter Scientists

Tropical Storm Arthur brought historic rainfall to portions of Louisiana, with some areas reportedly receiving up to 30 inches of rain in a single day. The resulting flooding and prolonged saturated soil conditions caused widespread damage to soybean fields across the central Louisiana region. Preliminary estimates indicate that approximately 114,000 soybean acres were affected, including nearly 38,000 acres with complete crop loss. An additional 15,000 acres were prevented from being planted due to excessive rainfall and persistently wet field conditions. Many remaining fields suffered partial losses that may reduce yields below levels needed to cover production costs. Overall, the total economic loss to Louisiana soybean production is currently projected to be approximately $33 million. Following the flooding, many soybean fields developed extensive yellowing (chlorosis) and dead leaf tissue (necrosis), leading to concerns about disease outbreaks. However, much of this injury is more consistent with flood-related stress than with a primary foliar disease.

When soils remain saturated for several days, oxygen levels in the root zone decline rapidly, impairing respiration and limiting the plant’s ability to absorb water and nutrients. As root function deteriorates, plants commonly develop chlorosis, nutrient deficiency symptoms, and eventually necrosis as leaf tissue dies. In addition, the hot and sunny weather that followed the storm likely intensified plant stress. Flood-damaged root systems often cannot absorb enough water to meet plant demand, reducing the plant’s ability to cool leaves through transpiration. As a result, leaves may become more susceptible to heat and solar injury, resulting in a scorched appearance and additional necrosis. Unlike most foliar diseases, which typically produce distinct lesions or recognizable disease patterns, flood injury often appears as generalized yellowing and tissue death across large portions of plants and entire areas of a field, particularly in low-lying sections where water remained the longest. Although disease organisms may later colonize stressed or dying tissue, the symptoms observed in many Louisiana soybean fields following Tropical Storm Arthur are likely the direct result of oxygen deprivation, root injury, reduced nutrient uptake, and subsequent heat and solar stress associated with prolonged flooding rather than a primary disease outbreak.

Figure 1. (Left) Mr. Tommy Laborde shows how high the water was above the soybean plants. (Right) Corn cobs were found on the top of the soybean canopy.

Figure 2. Partial soybean damage was seen across entire fields with complete plant death in the lower lying areas.

Figure 3. Yellowing (Chlorosis) andleaf tissue death (necrosis) was seen on all plants across entire fields.

Figure 4. Chlorosis and necrosis symptoms on individual leaves.

Figure 5. Differences in flood tolerance were seen across varieties.

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