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Chlorotic leaf distortion (CLD) develops on young leaves near the vine terminals, especially during humid, sunny days in July and August. It is caused by a fungus, Fusarium denticulatum, that grows on the outside of the shoot tip, but does not grow on older leaves or inside the plant.
Depending on the foliage of the cultivar affected, the youngest opened leaves may either turn bright yellow, or, if they normally are purple, they may turn pink. White flecks on the upper surface of older leaves are clumps of mycelia of the fungus that cause the disorder.
When humid sunny weather persists, the symptoms may be severe and some necrosis may occur on leaf margins. It is not known what effect CLD has on the quality of the vines, which in some countries are consumed by humans or fed to animals. No significant effect on yield of storage roots has been observed, even when foliar symptoms were severe.
Please direct questions or comments about sweet potato diseases to Chris Clark.