Pest and Disease Control Methods for the Chinese Medicinal Herb Alpinia oxyphylla
Diseases
Leaf Rot: Alpinia oxyphylla seedlings are susceptible to this disease, while mature plants rarely develop it. The main causes are high soil moisture or continuous rainy days. When the climate remains humid for a long time, the disease spreads rapidly. The affected parts are mainly the tender leaves; the lesions are light green and appear scalded, later turning brown and withered.
Control methods: (1) Promptly prune diseased leaves in the early stage of the disease; when severe, pull out the plants. (2) Chemical control: spray with 1:1:100 Bordeaux mixture or 0.2-0.5 degrees Baume lime sulfur mixture to control the spread of the disease. Apply once every 7-10 days, for 2-3 consecutive times. (3) Clear debris from ditches, promptly dredge and drain standing water; open the shade shed in the morning and evening on cloudy and sunny days to increase ventilation and light, accelerate water evaporation, and improve disease resistance. (4) Seedlings must not be sown too densely.
Root Rot: This disease mainly harms seedlings, while mature plants rarely develop it. The causes are similar to leaf rot. Under high temperature and high humidity, the damage is severe, and seedlings die in patches. The affected part is the base of the rhizome, which rots.
Control methods: (1) Improve ventilation and light conditions, open ditches to drain water promptly, appropriately increase light, improve plant disease resistance, and reduce disease occurrence. (2) In the early stage of the disease, pull out diseased plants, spread lime to disinfect and sterilize, and control the spread of pathogens. (3) Chemical control: use 1% copper sulfate solution for soil disinfection; spray the leaf surface with 1:1:120 Bordeaux mixture; alternately spray 500 times metalaxyl plus 500 times 25% carbendazim wettable powder for control, once every 7-10 days, for 2-3 consecutive times.
Sunscald: The leaf surface of Alpinia oxyphylla is delicate; any plants with poor shade or excessive nitrogen fertilizer application will develop sunscald once exposed to strong light. Symptoms: leaves dehydrate and wilt, tender heart buds scorch, until the plant dies. According to a survey by Xinglong Overseas Chinese Farm of wild Alpinia oxyphylla in nearby mountainous areas, during the natural regeneration period of tall trees, in places where the shade density does not reach 80%, the incidence of sunscald in wild Alpinia oxyphylla is 0.5%-1%. According to surveys in Wanning County and Lingshui County, for cultivated Alpinia oxyphylla with poor shade, sunscald is extremely common, with an incidence of 20%-30%, and in severe cases up to 70%-90%. The causes of sunscald: first, poor shade, with no shade trees planted before planting in plain areas; second, when planting Alpinia oxyphylla on hillsides, for fear of insufficient sunlight, the original trees were cut down excessively or completely; third, planting on cloudy and rainy days, or not watering enough to settle the roots during drought, or simply not watering at all; after planting, with little rainfall, exposure to scorching sun, and no timely watering, sunscald will occur severely.
Control methods: (1) Plant fast-growing plants around the area, such as pigeon pea (called liudou in Hainan), tephrosia, roselle, wild soybean, cassava, etc., as short-term shade. The specific method is: plant 1-2 plants of pigeon pea etc. 30 cm to the east and west sides of the Alpinia oxyphylla plants. (2) Replant fast-growing trees as shade trees, such as Chinaberry. (3) Plant Chromolaena odorata around the plants to block strong sunlight from the east and west directions; at the same time, Chromolaena odorata can be turned under as green manure, increasing organic matter, improving soil texture, enhancing water storage and retention capacity, promoting the growth of Alpinia oxyphylla, and strengthening resistance to diseases. (4) Establish good drainage and irrigation facilities; during dry seasons, divert or pump water for irrigation to keep the soil moist and reduce disease occurrence.
Damping-off: A disease caused by a fungus, mainly harming leaves; in severely affected areas, the incidence is 90%, and the mortality rate is over 35%. The pathogen spreads through rain, flowing water, transfer by farm tools, and the use of contaminated fertilizer. Sowing too densely, poor light and ventilation, and overly wet seedbed soil favor disease occurrence; climatic conditions with relatively high temperatures (above 28°C) and excessive rain easily cause disease epidemics.
Control methods: The seedbed should be selected in a higher terrain with good drainage; if using an old seedbed, 15-20 days before sowing, loosen the bed soil and drench with 100 times formalin solution, 5 kg per square meter, then cover with plastic film and seal for 4-5 days before uncovering, and sow after about 10-15 days; the fertilizer used must be decomposed, sowing should be uniform, and not too dense; watering the seedbed should not be excessive, avoiding overly wet bed soil; in winter, do a good job of insulation to prevent seedlings from freezing; in the early stage of the disease, drench the soil around diseased plants with 5% lime water or broadcast 1:50 phygon fine soil, or spray diseased plants with 50% carbendazim wettable powder 1000 times solution or 1:1:100 Bordeaux mixture; after pulling out severely diseased plants, spread lime powder around them or spray 50% thiophanate 1000 times solution.
Ring Spot Leaf Blight: Caused by a fungus. From seedling to fruiting stage, plants are susceptible to infection, with old leaves developing the disease first. The pathogen overwinters as mycelium or acervuli on diseased plants and their residual tissues. In the following spring, when environmental conditions are suitable, the pathogen produces conidia, which spread through wind and rain, mainly invading through wounds to cause disease. Hot and rainy seasons favor the expansion and spread of the disease; areas with year-round shade and humidity or poor drainage have particularly severe incidence; plants under extensive management, with severe sun exposure, and poor growth are prone to the disease.
Control methods: Strengthen management, increase fertilizer application, drain standing water, remove fallen leaves, and provide appropriate shading; in the early stage of the disease, spray with 50% amobam wettable powder 800 times solution or 1:1:100 Bordeaux mixture or 75% junqing 1000 times solution or 50% thiophanate wettable powder 800 times solution.
Root-knot nematode disease: Caused by a root-knot nematode. It mainly harms the roots of seedlings.
Control methods: Use disease-free seedlings; practice crop rotation; before sowing, deep plow and sun-bleach the seedling land, clear weeds inside and outside the nursery, and apply decomposed fertilizer to reduce sources of infection; 10 days before sowing, use 80% dichloropropane emulsion 3 kg mixed with 100 kg water per mu, apply in furrows, and cover with soil after application.
Pests
Alpinia oxyphylla skipper (also known as "leaf-rolling worm"): The larvae harm leaves, first making the leaves into roll-shaped leaf bracts, then feeding inside the leaf bracts, causing the leaves to appear notched or holed.
Control methods: Manually remove rolled leaves with insects or pinch the larvae to death by hand; during the larval occurrence period, trial spray with 90% trichlorfon 800-1000 times solution or 80% dichlorvos 1500-2000 times solution, once every 5-7 days, for 2-3 consecutive days.