Occurrence and Control of Stem Base Rot in Schisandra

Stem base rot in Schisandra can cause the stem base of the plant to rot, the root bark to fall off, and eventually the entire plant to die.

With the expansion of cultivated area, the occurrence of stem base rot in Schisandra has shown an upward trend. The general incidence rate is 2%-40%, and in severe cases it exceeds 70%, making it a devastating disease.

1. Disease symptoms Stem base rot occurs on Schisandra of all ages, with 1-3 year old plants being the most severely affected. The disease starts from the stem base or the junction of root and stem. In the early stage of the disease, the leaves wilt and droop as if lacking water, but cannot recover, and the leaves gradually dry up, finally the entire aboveground part dies. In the early stage of the disease, peeling back the cortex at the stem base reveals a small amount of yellowish-brown discoloration; in the later stage, the cortex of the affected part rots and turns dark brown, and easily falls off. When the diseased part is cut longitudinally, the vascular bundles turn dark brown. When conditions are suitable, the lesion expands upward and downward, causing the underground root bark to rot and fall off. When humidity is high, pink or white mold layers can be seen on the diseased part; picking up a small amount for microscopic observation reveals large numbers of Fusarium spores.

2. Disease pattern Through preliminary identification, the disease is caused by 4 species of Fusarium fungi, namely Fusarium equiseti, Fusarium solani, Fusarium oxysporum and Fusarium semitectum. These fungi can all be isolated from diseased plants, with proportions varying among different regions. The pathogen is mainly spread through soil. Schisandra can develop the disease from early May to late August, with disease onset in early May and peak incidence in early June. High temperature and high humidity, and rainy years lead to severe disease, and the disease tends to increase after rain followed by clear weather. Underground pests, soil nematodes, wounds caused during transplanting, and poor root development of plants all favor disease occurrence. Sustained low temperatures in winter causing frost damage easily leads to severe disease occurrence the following year; Schisandra growing in waterlogged low-lying areas is prone to the disease.

In production, false seedlings are mostly used for transplanting. In autumn, Schisandra seedlings are stored underground in bundles for several months, then transplanted to the field the following year. During this period, pathogenic fungi in the soil easily invade the plants, causing them to carry the pathogen. Schisandra sustains wounds during the transplanting process and has a relatively long seedling recovery period, during which the plants grow weakly and pathogens easily infect them. As the plants grow and the phloem thickens, the branches and trunk become thicker and the tree vigor increases, making it difficult for pathogens to invade. In planting areas, perennial Schisandra plants show varying degrees of disease; under the same cultivation conditions, 2-year-old Schisandra is the most severely affected, followed by 3-year-old, and 4-year-old and older Schisandra is the least affected.

3. Control techniques (1) Strengthen field management, pay attention to garden sanitation, promptly pull out diseased plants and burn them in a centralized manner, and drench the soil of the diseased holes with 50% carbendazim 600x solution; apply nitrogen fertilizer appropriately, increase phosphorus and potassium fertilizer to improve plant disease resistance; drain water promptly after rain to avoid waterlogging in the field; avoid planting Schisandra in plots where the previous crop had severe Fusarium disease. (2) Disinfect seedlings, and select healthy disease-free seedlings for planting. Soak seedlings in 50% carbendazim 600x solution or mancozeb 600x solution for 4 hours. (3) Chemical control. This disease should be prevented mainly. Before disease onset or in the early stage of disease, spray with 50% carbendazim wettable powder 600x solution, so that the solution can flow along the branches into the soil; spray once every 7-10 days, for 3-4 consecutive sprays; or use Lyuheng No. 1 (hymexazol) 4000x solution for root drenching.