In ginkgo tree cultivation, what is ginkgo stem rot?
What is ginkgo stem rot? What harm does ginkgo stem rot cause? At what tree age does ginkgo stem rot mainly occur? How is ginkgo stem rot prevented and controlled? Please give an introduction. Ginkgo stem rot mainly occurs in seedling-raising areas, generally in 1- to 2-year-old ginkgo seedling trees grown from seed, and is especially severe in one-year-old seedlings, often causing large numbers of seedlings to...
What is ginkgo stem rot? What harm does ginkgo stem rot cause? At what tree age does ginkgo stem rot mainly occur? How is ginkgo stem rot prevented and controlled? Please give an introduction.Ginkgo stem rot mainly occurs in seedling-raising areas, generally in 1- to 2-year-old ginkgo seedling trees grown from seed, and is especially severe in one-year-old seedlings, often causing large numbers of seedlings to die.
Symptoms of ginkgo stem rot:In the early stage of stem rot, the base of the seedling turns brown, the leaves lose their normal green color and droop slightly downward, but do not fall off. The infected area spreads rapidly upward, until the whole plant withers and dies. The cortex at the base of the diseased seedling becomes shrunken, and the tissue inside the bark rots into a spongy or powdery form, grayish white in color, and mixed with many tiny black sclerotia.
The pathogen of this disease can also invade the xylem of the seedling, so small sclerotia are sometimes also seen in the brown, hollow pith. After that, the pathogen gradually spreads to the roots, causing the root cortex to rot. If the diseased seedling is pulled up by hand, only the xylem can be pulled out, while the root cortex remains in the soil. In ginkgo cuttings, stem rot can also occur under high-temperature or low-temperature conditions, causing the epidermis of the cuttings to remain like a tube sheathing the xylem, while the parenchyma tissue of the phloem all turns black and rots.
Causes of ginkgo stem rot:The stem rot pathogen usually lives saprophytically in the soil and is a weakly parasitic fungus. Under suitable conditions, it invades through wounds on the seedlings. Therefore, the occurrence of the disease is related to the host and site environmental conditions. The fundamental cause of seedling damage is that the soil surface temperature is too high, and after the base of the seedling is scorched by high temperature, the pathogen invades.
The lower the degree of lignification of the seedling, the higher the incidence of this disease. When the seedbed is low-lying and waterlogged, the incidence also increases noticeably. In ginkgo cuttings, in June to August, when the seedbed high temperature reaches above 30°C, the disease begins 10 to 15 d after cutting, and in severe cases large areas of scions turn black and die. Experiments have shown that antagonistic actinomycetes can effectively inhibit the spread and diffusion of this disease pathogen.
Prevention and control methods for ginkgo stem rot:
Based on the causes of ginkgo stem rot, prevention should currently be the main approach.
1. Sow early. Sow as soon as the soil thaws. This measure helps the seedlings lignify early and enhances their ability to resist high soil surface temperatures.
2. Reasonable dense sowing. Dense sowing helps give play to the collective effect of the seedlings and enhances resistance to adverse external conditions. Experiments have shown that the smaller the seedling density, the higher the incidence; the greater the density, the lower the incidence. Practice has also shown that where 25 to 40 kg of seeds were previously sown per mu, if this is changed to a sowing rate of 80 to 100 kg of seeds per mu, not only is the incidence reduced, but the number of seedlings produced per unit is also increased, which both saves land and reduces disease occurrence.
3. Control underground pests. After seedlings are damaged by underground pests, they are extremely susceptible to infection by the stem rot pathogen. Therefore, before and after sowing, always pay attention to eliminating underground pests.
4. Prevent mechanical damage to seedlings. For seedlings sown in the current year or one-year-old transplanted seedlings, during loosening soil and weeding or during lifting and planting of seedlings, be sure not to damage the roots and stems of the seedlings; otherwise, stem rot is very likely to occur.
5. Shade and cool down. To prevent solar radiation from raising the soil temperature, seedling-raising land should adopt measures such as building shade frames, covering grass between rows, planting corn, and inserting branches for shade, so as to reduce harm to the seedlings.
6. Irrigation and spraying water. In hot seasons, irrigate and spray water in a timely manner to lower the surface soil temperature. Where conditions permit, sprinkler irrigation can be adopted, which is even more helpful in reducing the occurrence of the disease.
7. Chemical and biological control. Combined with irrigation, various fungicides such as thiophanate-methyl, carbendazim, and Bordeaux mixture can be sprayed. In mid-June, when applying organic fertilizer as a top dressing, antagonistic actinomycetes can also be added, or plant ash/superphosphate (1/0.25) can be applied as a top dressing together with antagonistic actinomycetes.
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