In early growth stages, corn or soybeans can survive for only two to four days under water in anaerobic conditions. Moderate water movement can reduce flood damage by allowing some oxygen to get to the plants, keeping them respiring and alive. Drainage within one to two days increases the chance of survival. Cool temperatures may prolong survival. However, cold, wet weather favors disease development.
Seed treatments are effective, but limited in protection.
Seed rots, seedling blight, corn smut and crazy top affect corn plant development later even though ponding occurred earlier. Delayed soybean growth allows diseases such as Fusarium root rot, Phytophthora rot and Pythium rot to establish and weaken or destroy seedlings. Limited hybrid and variety resistance to these diseases and difficulty in predicting damage makes evaluation difficult. Carefully assess damage before deciding to replant. In soybeans, research through various areas of the United States have shown that yields are not affected by population reductions until stands drop below 125,000 plants per acre but yields can be lower if large gaps are present.