Latest Control Methods for Gastrodia Tuber Rot
Gastrodia tuber rot, also known as Gastrodia soft rot nest disease, is one of the reasons for low and unstable yields in Gastrodia cultivation. Affected Gastrodia tubers have yellowed, withered skin, rotting central tissue, and a foul-smelling white milky fluid oozing from the cut surface of the tuber. In the rotted nest of the Gastrodia planting hole and within the tuber, Armillaria mellea rhizomorphs grow abundantly and densely. Let us take a look together at the control methods for Gastrodia tuber rot!
Symptoms of Gastrodia Tuber Rot
In Gastrodia tuber rot, the skin of the tuber becomes yellowed and withered, the central tissue rots, and the interior of the tuber turns into a foul-smelling, thin slurry. Some upper-layer Gastrodia tubers rot and shrink, while others have partial rotting of the upper portion or necrosis of the cortical layer, whereas lower-layer Gastrodia tubers may or may not be affected.
Causes of Gastrodia Tuber Rot
1. Improper soil selection: Soft rot nest disease is mostly seen in hard gravelly soil and dead yellow mud soil with poor moisture retention and aeration. Armillaria mellea grows poorly in such sites, and Gastrodia withers and rots to death due to lack of nutrients from Armillaria mellea.
2. High temperature and high humidity environment: Under such climatic conditions, miscellaneous fungi grow readily. Grayish-white miscellaneous fungal hyphae quickly appear on the Armillaria mellea-infected wood, and gradually spread into the humus within the nest. Yellowish-white, rapeseed-shaped sclerotia form among the hyphae. Once infected by pathogenic fungi, Gastrodia begins to rot from a localized area and spreads.
3. Excessive rain and poor drainage: Under waterlogged conditions, Gastrodia growth is inhibited and its lytic function is significantly weakened. However, Armillaria mellea, due to its strong stress resistance, can still grow normally. Armillaria mellea breaks through the lytic layer of Gastrodia and rapidly proliferates within the tuber, “counter-attacking” it. This is characterized by rotting tubers filled with Armillaria mellea rhizomorphs beneath the skin, and densely packed Armillaria mellea rhizomorphs on the infected wood in the rotted nest. This rotting nest phenomenon mostly occurs during the rainy season.
4. Cultivation technique errors: This situation is mostly caused by insufficient infected wood, excessive seeding rate, and insufficient humus filler in the hole. Due to inadequate nutrient supply from Armillaria mellea, Gastrodia grows slowly and becomes thin and weak, gradually leading to soft rot.
Control of Gastrodia Tuber Rot
1. Choose sandy loam soil with good granular structure, strong water permeability, and rich humus content, and require forest land with a 15-25° slope. The soil pH should be 5.8-6, and the humidity should be 40%. In high mountain areas, choose sunny slopes; in mid-to-low mountain areas, choose semi-sunny slopes; in low hills and hilly areas, choose understory cultivation.
2. The cultivation season is generally scheduled mainly in winter (October-November). Usually, old infected wood is combined with new infected wood to supplement the nutrients of Armillaria mellea-infected wood and control excessive growth of Armillaria mellea. During cultivation, open the fungal bed cultivated in March-April of that year, take out 5 well-developed pieces of infected wood and add 4 new pieces to plant another nest, then add 4 new pieces to the original fungal bed to plant one more nest (i.e., the “take five, add four method”). Generally, 500-750 grams of seed tubers are planted per 10 pieces of infected wood, with the seed tubers placed close between the infected wood pieces, and more fungal branches added between new wood pieces. Besides laying a layer of oak leaves at the bottom of the hole, each planting layer is filled with an appropriate amount of oak leaf humus soil. After planting, cover with leaves and then cover with soil 10-15 cm.
3. Gastrodia management is simple: no weeding, no fertilizing, mainly preventing drought, waterlogging, and cold, and preserving soil moisture. In low mountain areas, to prevent drought, plant a few corn plants beside the hole as drought indicator plants; when corn leaves curl, spray an appropriate amount of water to prevent drought. During the rainy season, dig ditches on the upper slope of the cultivation area for drainage. In high mountain areas, cover with leaves or straw mats to prevent freezing during the cold winter season. In addition, prevent trampling by people and livestock and contamination by pesticides.
4. Strictly select infected wood and fungal beds. When planting Gastrodia, strictly select infected wood and fungal beds. If any infected wood is contaminated by miscellaneous fungi, it is better to discard it than to use it. Pay attention to cold protection measures at ordinary times. For spring Gastrodia, take cold protection measures during overwintering to ensure safe overwintering. If safe overwintering cannot be achieved, harvest before overwintering.