Pest and disease control:
1.猝倒 disease: Also known as lodging disease, it primarily occurs within two months after seedlings emerge or within half a month after seedlings are transplanted. The pathogen invades from the roots, causing brown spots, expanding lesions that appear water-soaked, and tissue necrosis. The affected area can cause the seedlings to fall over rapidly. The disease is more likely to occur when the seedbed is waterlogged, the soil covering is too thick, the topsoil is compacted, and the ground temperature is too high.
Control Methods: Spray 0.5% Bordeaux mixture on the stems and leaves of seedlings, then rinse the seedlings with clean water after spraying.
2. The pest primarily affects caterpillars or grasshopper larvae, which hide in the soil during the day and emerge at night to feed on unemerged seedlings or chew off the base of seedlings at ground level. They may also climb up to the top of seedlings and eat tender stems and buds, affecting their growth.
Control Methods: Remove weeds, destroy eggs, and prevent larvae on the weeds from transferring to seedlings for harm. In the morning, around areas with missing or broken seedlings in the nursery, dig up the soil to capture larvae; spray with a 90_0010_00 solution or a 300-fold spray of 20% emulsion oil to kill insects.
3. Anthrax disease: Primarily harmful to leaves, the early stages show faint brown-green spots on the leaf surface. As the spots expand, they form circular or irregular lesions with a diameter of 0.6-1 cm. The edges are purplish-brown, the center is yellow-brown to grayish-white, with occasional concentric rings and scattered small black dots. The lesions can also merge into larger ones. The peak period for occurrence is from June to September when the weather is humid, rainy, and warm.
Control Methods: In winter, clear away withered branches and leaves, and burn them to greatly reduce the source of primary infection in the coming spring; promptly remove and destroy any small number of diseased leaves; during the early stage of the disease, spray the plants alternately with a concentrated solution of 0.125% of 75% chlorothalonil wettable powder or a 0.1% concentration solution of 70% metiram wettable powder.
4. Sunscald: During seedling cultivation, intense sun exposure after prolonged rainy weather can easily cause sunscald in seedlings. Symptoms include the entire plant and upper leaves losing their green color, with the leaf surface turning grayish-white to gray-brown, and some areas may exhibit fading. Mild cases show circular brown spots with brown edges, light in color, while severe cases result in the entire leaf turning brown, withering, and eventually dropping off.
Control Methods: After entering the high-temperature season, promptly set up a canopy over the seedling bed with sugarcane leaves; maintain the seedling bed moist, and frequently spray water on the plant leaves; applying a 0.1% solution of 96% copper can enhance the plant's heat resistance.
Early spring planted Luchang smile trees, during the seedling stage from April to May, enjoy favorable climatic conditions, making it suitable for seedling transplantation. The seedlings sown on seedling beds are now quite dense, necessitating sales or bed transplantation during this period. For seedlings sown in large field nurseries, it is also essential to take advantage of the favorable climate to promptly carry out thinning and final planting, utilizing some thinned seedlings for transplantation and supplementation, eliminating inferior seedlings, adjusting seedling density, ensuring a certain yield per unit area, and creating conditions for seedling cultivation. Irrigation should be conducted after thinning or later to ensure the loosened root systems of the seedlings are closely combined with the soil.
The growth condition of Leshan Ham笑 seedlings during their peak growing period largely determines the seedling quality. At this stage, seedlings grow rapidly with significant increases in height, ground diameter, and root system, with height growth being particularly prominent and forming lateral branches. The main external factors affecting seedling growth and development are temperature, soil moisture, and nutrients. It is necessary to set up shade houses to prevent leaves from being severely sunburned. Timely irrigation is required during dry and hot periods, and timely drainage should be done during the rainy season of the plum blossoming period. Leshan Ham笑 dislikes waterlogged soil; if waterlogging persists for more than a day, it can lead to high seedling mortality rates. Additionally, proper aeration, weed control, and pest and disease prevention should be conducted. Fertilization should be applied during the two rapid growth periods, excluding the slow growth period from July to August, to meet the needs of vigorous seedling growth.
Cultivation Techniques:
1. Seed Collection: Select seeds from robust female trees between 20-40 years old. From mid-October to early November, when the aggregate fruits change from green to reddish-brown, harvest them using a seed knife or pruning shears. Spread them thinly in a cool, well-ventilated area for ripening. Once the fruit shells crack, remove the seeds, or place the fruits outdoors to dry for several days before bringing them indoors, then remove the seeds after cracking. Remove the false seed coats and plant the seeds immediately after collection. The thousand-grain weight is 260-300 grams, with a germination rate of 80%.
2. Sowing: Seed can be sown indoors on seedling beds or outdoors in nurseries with good irrigation conditions, ideally on deep, fertile sandy loam soil. Thorough soil preparation is required before sowing, including loosening the topsoil, removing weeds, and leveling the ground. Organic fertilizers such as compost, stable manure, and green manure can be added as base fertilizers, as well as a small amount of nitrogen and some phosphorus and potassium to improve soil quality and ensure a continuous supply of nutrients for seedling growth. In indoor or warmer regions, sowing can be done in early February. In outdoor or colder areas, it is generally done after the soil thaws in March. Before sowing, seeds can be soaked in water below 40℃ for 12-24 hours to absorb sufficient moisture, accelerate germination, and ensure uniform emergence.
Based on the different purposes of seedling cultivation by growers, various sowing methods can be employed. If the grower plans to sell seedlings or transplant beds during the seedling stage, the broadcast sowing method can be used, which involves evenly sowing seeds across the entire seedling bed. Broadcast sowing maximizes land use, results in high seedling density, and evenly distributed seedlings with a high yield per unit area. However, the drawback is that seedlings remain in the bed for a short period, and growers must be prepared for transplantation. If the grower does not plan to sell seedlings or transplant in the same year, the row sowing method can be adopted, where seeds are evenly scattered in trenches created at a certain distance on the seedling bed. Typically, rows are 5 cm wide, spaced 25 cm apart, with trenches 1.5-2 cm deep. After sowing, cover the seeds with 1-2 cm of soil and water thoroughly. Cover the seedling bed with straw to maintain humidity, and then uncover the straw in stages as the seeds germinate.
3. Seedling Raising: The period from the emergence of seedlings after sowing to the time they can stand independently is known as the seedling emergence stage. The Leshan Amomum can germinate within 20-30 days after sowing, and the seedling emergence stage lasts for about 15-20 days. During this period, the seedlings are very tender and weak, with shallow root distribution and low resistance. The key to seedling raising is to provide a favorable environment for seed germination and seedling emergence, ensuring the necessary moisture and aeration for seed germination. However, the seedbed should not be overly wet or waterlogged, as excessive moisture can lead to poor aeration, affecting seed development and causing seed rot. At this stage, the tender seedlings cannot produce nutrients on their own, and their nutrient source is primarily the stored nutrients from the seeds, so fertilization is not required.
4. Seedling Stage: The period from when the Leshan Osmanthus seedlings emerge from the soil to the start of their vigorous growth is known as the seedling stage, lasting approximately 20 days. During this period, the seedlings begin to develop true leaves, start photosynthesis to produce organic matter, and the number of leaves gradually increases. The root system grows rapidly, producing lateral roots. At this stage, the seedlings are still very tender, with low resistance to adverse external conditions and a high mortality rate. Measures should be taken to prevent phenomena such as drought, waterlogging, high temperatures, and low temperatures. Provide adequate shading, remove weeds and loosen the soil early, and pay attention to pest and disease control. The seedling stage has a low demand for nutrients, but if a moderate amount of thin nitrogen and phosphorus fertilizer is applied, it can improve the quality of the seedlings.
5. Growth Peak: The growth peak of seedlings is from the time when the height growth increases significantly to when it decreases significantly. The growth peak of Leshan Osmanthus starts from mid-May to mid-October, with a growth peak from early May to early July, during which the seedling height can reach 20-25 cm. From July to August, it is the hot and dry summer period, with slow growth. Another growth peak appears from September to October, with an average height growth of about 30 cm.
