Symptoms The roots of the diseased roots are entangled with roots, beginning with white, and then turning gray-brown. The roots are rotten. After peeling, the mycelium can be seen as fan-like, clinging to the xylem and forming sclerotia. The diseased tree gradually weakened and eventually died. Shanxi, Jiangsu, Guangdong and Sichuan all happened.
Pathogen Rosellinia necatrix (Hart.) Berl. Brown shell is known as Ascomycota subphylum fungi. The mycelial membrane that is parasitized on the surface of the mulberry trunk is formed by the cross-hybridization of many hyphae. The mycelium inside the mycelium membrane is a thin-walled mycelium with a diameter of 2 μm and less than 1 μm. The external hyphae are thick-walled hyphae, with a diameter of 4 μm, a membrane at 37-65 μm, and a plow-shaped bulge. This is an important feature of the bacteria. The diameter of plowing cells is 7-8um, and it often forms crusted spores for reproduction. The mycelium of the pathogen invades from the internal tissues of the root and separates the cork layer from the xylem. After the cortex was completely rotted, a massive, dark brown nucleus was produced in the xylem with a size of 10.5 (mm). The fungus grows branched spores at the base of the stem, 15 to 20 branches on one main branch, conidia at the ends, conidia oval to long oval, unit cells or 2-3 Cell, size 7.252.50 (um). All the diseased trees are rotted, and the vegetative mycelium develops into a state of decline after it enters into a sexual state. The ascospora shells are produced in the stems of the spores of the roots. They are spherical, basal short, black outer wall, inner wall colorless, containing ascaria and lateral filaments. The capsule is cylindrical and has a slender stalk, 200-3005-47 (um) in size, with an oval-shaped small piece at the top of the capsule and 8 ascospores in the ascus. Ascospores are long spindles, with sharp ends, dark brown, size 407 (um).
Transmission routes and pathogenic conditions The pathogens are overwintering with rhiform bacteria, sclerotia, parasitic or saprophytic in the soil. The germs are infected by contact with mulberry roots, and the bacteria are often between 1-10 cm on the soil surface. The optimum temperature for pathogenic bacteria growth is 25°C, the soil moisture is 60%-80%, and the mycelium grows quickly. The disease occurs from year to year and spreads rapidly from May to August. Newly built mulberry hills in mountainous areas are vulnerable to disease.
See the control method for Mori purple feather disease.
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