Crown and spear rot

Phytophthora spp., Phytophthora megasperma

Phytophthora spear rot is characterized by soft, water-soaked lesions on shoots at, slightly above, or below the soil level. The lesions elongate rapidly and become light brown. As the lesion collapses and shrivels, the affected side of the spear becomes flattened, and the shoot becomes extremely curved and may even collapse. This symptom is not diagnostic, however, as insect and mechanical injury can result in crooked spears. Infected young storage roots appear water soaked but firm.

Crowns infected with Phytophthora spp. have yellow-orange colored tissue. In severe infections the tissue appears waterlogged and fibrous.

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