As a valuable medicinal plant, Hou Po has high medicinal and economic value. In addition, the Hou Po tree itself has stronger resistance to diseases compared to other plants, and the occurrence of diseases is not very prominent. Therefore, there are more and more people planting Hou Po trees. Currently, the common diseases of Hou Po trees are wilt disease, leaf blight, and root rot.
1. Wilt Disease
(1) Pathogen
Wilt disease is caused by a fungus belonging to the subphylum Ascomycota, class Sordariomycetes, order Hypocreales, family Hypocreaceae, and genus Fusarium.
(2) Symptoms
Wilt disease of Hou Po often occurs during the seedling stage. When the seedlings emerge from the ground, it is necessary to carefully observe the planting base near the ground, where you can see the shrinkage and rotting, appearing as dark brown or black-brown depressed spots. The seedlings gradually show symptoms of wilting and falling.
(3) Occurrence
The pathogens overwinter as mycelium or sclerotia in the soil and infected tissues. The disease often occurs during summer rainy weather, in low-temperature and high-humidity soil, and when the seedlings are too dense.
(4) Control Measures
① Prevention is the main approach, and attention should be paid to selecting well-drained and well-ventilated neutral sandy soil for seedling cultivation.
⑦ During the rainy season, good drainage and ditch cleaning should be done in the seedbed and seedling area to reduce the moisture and increase the air permeability in the field.
③ In the early stage of disease occurrence, 5% lime solution can be used for irrigation, every 6 days, irrigate once, and repeat 2 to 4 times to prevent further spread. During the disease occurrence period, irrigate the area around the diseased plants with a 5% carbendazim solution diluted 1000 times.
2. Leaf Blight
(1) Pathogen
Leaf blight of Hou Po is caused by a fungus belonging to the subphylum Ascomycota, class Dothideomycetes, order Capnodiales, family Mycosphaerellaceae, and genus Mycosphaerella.
(2) Symptoms
Leaf blight often occurs on the leaves of Hou Po. When the disease occurs, the leaf surface shows circular dark brown spots with a diameter of 2.5 to 5 mm, which gradually expand and become densely distributed on the entire leaf. During humid conditions, the spots have small black dots, which are the conidia of the pathogenic fungus. In the late stage, the diseased leaves become dry and withered.
(3) Occurrence
Leaf blight often occurs during the seedling stage and in plants that are 2 to 3 years old. The pathogen overwinters as conidia in the soil or infected tissues. In the following year, when the conditions are favorable, conidia are produced. The optimal temperature for conidia production is 26 to 28 degrees Celsius. Conidia are mainly spread by wind and rain, so the disease is more severe in summer when there is more rainfall.
(4) Control Measures
① During the rainy season, stagnant water should be promptly removed.
② Attention should be paid to fertilization, and nitrogen, phosphorus, and potassium should be properly balanced to promote the healthy growth of seedlings and enhance their resistance to bacteria.
③ In the early stage of disease occurrence, diseased leaves should be timely removed and burned or deeply buried to eliminate the source of infection.
④ At the same time as eliminating the source of infection, 1:200 Bordeaux mixture can be sprayed every 10 days for 2 to 3 times. Alternatively, 50% carbendazim diluted 500 to 1000 times or 40% chlorothalonil diluted 1000 times can be sprayed every 10 to 15 days for 2 to 3 times. Another option is to spray 70% methyl thiophanate wettable powder diluted 1000 to 1500 times every 7 to 10 days for 3 to 4 times.
3. Root Rot
(1) Pathogen
Root rot of Hou Po is caused by a fungus belonging to the subphylum Ascomycota, class Sordariomycetes, order Xylariales, family Xylariaceae, and genus Hypoxylon. The conidia are crescent-shaped, colorless, septate, and abundant.
(2) Symptoms
Root rot easily occurs in young seedlings and small trees under 4 years old. The roots first turn brown and gradually spread, appearing as water-soaked spots. In the late stage, the diseased roots become black and rotted, and the seedlings wither and die.
(3) Occurrence
The pathogen overwinters as conidia in the soil or infected tissues. In the following year, from June to August, when the weather is suitable with intermittent rain or heavy rainfall, and the plants are waterlogged and the seedlings are not growing well, root rot is likely to occur.
(4) Control Measures
① During the growth period, loosening the soil and fertilizing should be done to promote the vigorous growth of seedlings and enhance the plant's resistance. During the rainy season, ditches should be cleaned frequently, and drainage should be promptly done when there is stagnant water in the seedbed to reduce the humidity.
② In the early stage of disease occurrence, it is recommended to use a 50% carbendazim solution diluted 500 to 1000 times or a 40% thiram solution diluted 1000 times, spraying every 10 to 15 days for 2 to 3 times.
