Detailed Explanation of Symptom Identification and Control Methods for Fusarium Wilt in Silk Trees

The silk tree, also known as the velvet flower tree or the Persian silk tree, is a plant that blooms in summer, with flowers mostly in pink and a rather unusual shape, like a feather fan. The wood of the silk tree is very suitable for making furniture, railway sleepers and so on, because its structure is relatively fine, its grain is very straight, and its color is reddish brown. Silk trees are planted in many places in our country, and Fusarium wilt very easily occurs during the growing process. So what are the symptoms and control methods of this disease?

I. Symptoms of Fusarium wilt in silk trees

The symptoms of Fusarium wilt in silk trees mostly appear during the rainy season. The leaves on diseased branches wilt, droop, dry out and shrink; the diseased leaves on diseased branches sometimes remain green or turn yellow, and eventually the leaves fall off, generally starting with the leaves at the base of the branches turning yellow. The above symptoms often first appear on one or two branches, then gradually spread to other branches. When diseased branches and trunks are cut crosswise, the sapwood shows brown ring-shaped spots; when branches and trunks are cut lengthwise, brown longitudinal streaks appear in the vessel area of the sapwood. In late summer and early autumn, the symptoms of infection through wounds on diseased branches or trunks mostly spread upward and downward from the wound, the lesions sunken, with the pathogen's conidiomata and large amounts of pink powdery conidia; the symptoms of infection by the pathogen through wounds on branches and trunks mostly spread upward and downward from the wound, the lesions sunken, with the pathogen's conidial masses breaking through the bark cracks, producing clustered pink conidial masses, and the bark swelling and rotting.

This disease is mainly a systemic infection disease. The pathogen overwinters on diseased plants or with diseased residues in the soil. In spring and summer of the following year, when humidity and temperature are suitable, the pathogen can invade from root wounds or directly, and spread along the vessels up the tree to the vessels of the trunk and branches, poisoning and blocking the vessels, cutting off the transport of water, and causing the branches to wilt. Trees planted in patches in low-lying areas with abundant rain suffer severe damage.

II. Control methods for Fusarium wilt in silk trees

Given the characteristics of this disease, including a relatively long infection period, many transmission routes, a wide range of pathogen sources, systemic infection, and the difficulty of detecting it in the early stage of infection, once symptoms appear it is difficult to control. It is very difficult to achieve the goal of control by adopting a single control measure; comprehensive control is necessary to achieve the best control effect.

Choose suitable soil for planting. When planting silk trees, avoid low-lying areas at all costs; choose a place with loose soil and good drainage conditions for planting.

The planting arrangement should be scientific. It is best to plant a single tree or several trees in a green belt, or they can also be used as accents in gardens and courtyards; because street soil is solid and continuous and drainage is poor, it is not suitable to use them as street trees.

Improve the level of management. After planting, silk trees should be loosened regularly, protected from drought and drained of excess water, and fertilized regularly, with organic fertilizer applied once in spring and once in autumn. Mature trees should be given organic fertilizer; mix 4 to 6 kg of organic fertilizer per tree evenly with soil and apply it in pits, so as to enhance the disease resistance of the silk trees.

Chemical control. First, in summer, before the disease is seen, open holes one by one and pour in 50% thiophanate-methyl at 500 times dilution or 40% carbendazim at 600 times dilution. Second, for transplanted trees, the roots can be dipped in a 10% copper sulfate solution. For branch and trunk cut surfaces that have already been cut, apply a protective agent to prevent the pathogen from invading.