Occurrence and Control of Panax notoginseng Leaf Rot

Symptoms This disease can harm all aboveground organs except the roots. The most typical symptom is the formation of black spindle-shaped lesions at the top of the petiole. When temperatures are high, the lesions rapidly encircle the petiole and quickly spread to the base of the leaflets, forming light black water-soaked lesions on the leaves with irregular edges. The diseased part of the petiole quickly softens, causing the upper leaflets to droop (commonly known as "twisted-down plate"). On the diseased areas, pale yellow powdery masses tinged with pink are often visible, which are the fruiting bodies of the pathogen. When attacking the middle of the leaf blade, it forms black irregular lesions with irregular edges, generally 5-13mm in size; the diseased area rots, and when dry the edges are relatively neat, with the center easily falling out to form holes; flower clusters are easily damaged, with symptoms the same as those of petiole damage; when the stem is damaged, raised dark brown spindle-shaped lesions form, but they spread slowly.

Pathogen Verticillium cinnabarinum (Cda.) Reinke et Berth., called cinnabar verticillium, belongs to the Deuteromycotina fungi. On PDA medium, the colony is initially white, later orange-yellow; the hyphae are slender, nearly colorless, 1.6-2.2μm in diameter, septate, and can aggregate into bundles; in the mycelium, conidiophores can cluster together, and the conidiophores are clearly distinct from the hyphae, 40-82 x 1.4-1.7 (μm), branching at acute angles of 30-40 degrees, branching 2-3 times, with 1-6 phialides on the branches, verticillate, 9-13 x 1.4-1.7 (μm). Conidia are ovoid or long ellipsoid, sometimes slightly curved, single-celled, colorless, produced in extremely large numbers, 3-7 x 2-3 (μm) in size.

For transmission routes, disease conditions, and control methods, see Datura Verticillium Wilt.