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| Introduction Symptoms Disease Cycle Diagnosis/Sampling Management |
| SYMPTOMS Root rot symptoms appear early at 4-6 weeks after planting. Root rot first appears on the radicle and seminal roots as brown to black necrotic lesions (Fig 1). These lesions expand as the season progresses. In soils of high disease severity, the entire radicle eventually becomes discolored. Lesions develop on the nodal roots throughout the season (Fig. 2). The entire root ball may be rotted by the end of the season (Fig. 3). In addition, root mass is reduced. |
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 Figure 1. Initial symptoms begin as small lesions on the radical and seminal roots. |
 Figure 2. As the root system develops, more of the root system becomes infected. |
  Figure 3. Root ball on the left is 95% rotten. Root ball on the right is healthy. |
| Crown rot may be associated with root rot (Fig 4). Crown rot appears as very dark, water soaked tissue with an obvious margin between healthy and diseased tissue. Sometimes crowns may appear darker in color due to physiological or chemical factors, but this discoloration is not likely due to crown rot (Fig. 5). The impact on plant growth of these darker crowns is not known. | ||
 Figure 4. Crown rot appears as dark, water soaked tissue. |
 Figure 5. Crown discoloration - increasing in intensity from left to right. Crown discoloration is not crown rot. |
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| Secondary disease symptoms appear late in the growing season, between silking and harvest. Leaves become chlorotic, turning from yellow to brown. This leaf “firing” starts at the base of the plant and progresses upward (Figure 5). Yield and quality are reduced because ears produced on fired plants are smaller in size, tip fill is poor, and kernels may dimple (Figure 6). | ||
 Figure 5. Above-ground secondary symptoms include browning or “firing” of leaves starting at the base of the plant and progressing upward. |
 Figure 6. Secondary symptoms observed on the ears include small ear size, poor tip fill, and dimpling of kernels. Ears on the left are from diseased plants; ears from healthy plants are on the right. |
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