Why does Gastrodia elata have soft rotten nest? How to avoid the occurrence of this disease

Soft rot nest disease of Gastrodia elata is one of the reasons for its low and unstable yield in cultivation. Soft rot occurred in rice hemp, white hemp and arrow hemp, the tuber bark was yellow, the central tissue was rotten, and the section of the tuber exudated a stinky white serous liquid. Armillaria mellea is lush and dense in the burrow of Gastrodia elata and in the tuber. Gastrodia elata grows on Armillaria mellea. Why do soft rot nests and tubers fill with Armillaria mellea mycelium? In order to explore this problem, we should start with the nutritional ecology of Gastrodia elata.

Gastrodia elata has no roots and no green leaves, and its autotrophic organs degenerate. It depends on Armillaria mellea to provide nutrition and has a special life relationship with Armillaria mellea. The establishment of this kind of life relationship began when Gastrodia elata was used as host by Armillaria mellea and the hyphae came into contact with Gastrodia elata tuber.

The hyphae of Armillaria mellea generally extend along the tuber of Gastrodia elata. The outer cord sheath is initially brown-red with a white head, gradually black-brown, and the inner sheath is white hyphae. Armillaria mellea has strong adaptability to the environment and can grow and develop under soil temperature 6-32 ℃, but the most suitable soil temperature is 15-25 ℃ and soil moisture is 50%-70%. The developing Armillaria mellea not only gets nutrition from the host, but also constantly looks for new hosts around and extends. After contact with the tuber, the mycelium spreads quickly along the tuber epidermis and produces root hairy hyphae, which penetrates the tuber epidermis of Gastrodia elata and invades the bacteriolytic layer (located in the subcutaneous inner layer of Gastrodia elata tuber and arranged in a columnar line under the microscope). Continuously provide nutrition for the growth of Gastrodia elata. Therefore, in the environment beneficial to the growth of Gastrodia elata, the more Armillaria mellea hyphae invaded, the faster the tuber grew until the inner layer of Gastrodia elata hardened and the bud of the apical flower pavilion formed. However, because the adaptability of Gastrodia elata to the environment is weaker than that of Armillaria mellea, Gastrodia elata begins to grow when the soil temperature is above 10 ℃; it grows fast when the soil temperature is 15: 25 ℃ and the humidity is 40% ~ 50%; when the soil temperature reaches 28 ℃ and the humidity is above 60%, the tuber growth is inhibited, and the humidity above 70% will lead to Gastrodia elata necrotic and rotten nest.

The soft rot nest of Gastrodia elata is a physiological disease, which is mainly caused by poor environmental conditions.

The soil quality of ① is not selected properly. Soft rot nests are mostly found in ballast land and dead yellow mud land where soil moisture conservation and air permeability are poor. Armillaria mellea grows poorly in this site, and Gastrodia elata wilts and dies due to lack of Armillaria mellea nutrition.

② environment with high temperature and high humidity. In this climate, it is beneficial to the growth of miscellaneous bacteria, and the gray-white hyphae on Armillaria mellea quickly appear and gradually spread to the humus branches in the nest. The characteristic of the pathogenic bacteria is that it is better to see the yellow-white, rapeseed-like sclerotia between the harmful hyphae, and Gastrodia elata is infected by the disease bacteria, that is, from local to whole body rot.

③ is rainy and has poor drainage. Under such bad conditions, the growth of Gastrodia elata was inhibited and the bacteriolytic function was significantly weakened. However, Armillaria mellea can still grow normally because of its strong stress resistance. Armillaria mellea breaks through the dissolved layer of Gastrodia elata and propagates rapidly in the tuber. It is characterized by rotting tubers under the skin, full of Armillaria mellea cords that "eat" Gastrodia elata, and dense Armillaria mellea cords on the mushroom in the rotten nest. This kind of rotten nest phenomenon mostly occurs in the rainy season in July, August and September.

The technical error of cultivating Gastrodia elata with ④. This situation is often seen in the lack of fungus, the amount of seed is too large, and there are no oak leaves in the hole and other humus charge. Although there are climatic conditions suitable for the development of Gastrodia elata, due to the lack of nutrition from Armillaria mellea, Gastrodia elata is thin and long, which gradually leads to soft rot.

So how can we avoid the occurrence of soft rot disease of Gastrodia elata?

① selects sandy loam with good aggregate structure, strong water permeability and rich humus, and requires the woodland on the slope of 15 °~ 25 °, the soil pH value is 5.8 ~ 6 and the humidity is 40%. Sunny slopes are selected in high mountain areas, semi-sunny slopes in medium-shallow mountain areas, and cultivation under forest in low mountains and hills.

The cultivation season of ② is generally arranged in winter (October to November). The old fungus material and new fungus material are usually used to supplement the nutrition of Armillaria mellea and to control the overgrowth of Armillaria mellea. During cultivation, the bacterial bed cultivated from March to April of the same year was opened, 5 well-developed bacterial materials were taken out and 4 new materials were planted in another litter, and 4 new materials were added to the original bacterial bed to plant a litter (that is, "take five to add four"). Generally, every 10 fungi are planted under 500g to 750g, flax seed is close to the fungus, and more fungus branches are added between the new materials. except for a layer of oak leaves at the bottom of the hole, each layer is properly filled with oak leaf humus soil, and the soil is covered with 10cm of soil.

③ Gastrodia elata management is simple, no weeding, no fertilization, mainly to prevent drought, waterlogging, cold and soil moisture conservation. In low mountain areas, in order to prevent drought, several corn plants can be planted next to the hole as drought indicator plants, and appropriate amount of water can be sprayed to prevent drought when corn leaves are found. In the overcast and rainy season, trenches are opened up the slope of the cultivation area to drain water. In high mountain areas, it is necessary to cover leaves or grass curtains to prevent freezing in the cold winter. In addition, it is necessary to prevent human and animal trampling and pesticide pollution.