Analysis of Disease Control of Gladiolus in Protected Cultivation and High-Yield Cultivation Techniques for Edible Fungi
Gladiolus, also known as "shiyangjin," is a perennial bulbous flower of the genus Gladiolus in the family Iridaceae. As one of the world's five major cut flowers, it is commonly used to make decorations such as flower baskets, bouquets and vase arrangements, offering growers high economic returns. In protected cultivation, the occurrence of diseases will affect the normal growth of the plants and reduce the quality and ornamental value of the cut flowers. In severe cases, it can cause devastating damage. Preventing the occurrence and development of gladiolus diseases is the first issue that cut flower producers must consider.
I. Gladiolus Seedling Damping-Off
1. Symptoms
This disease occurs early and can cause seed rot. When it occurs at the seedling stage, water-soaked lesions appear at the base of the plant's stem. The lesions are light brown and slightly constricted, and can expand rapidly, gradually constricting the young stem into a thread-like shape. The disease develops very quickly; while the young leaves are still green, the seedling wilts and falls over, hence the name damping-off. Finally, the diseased seedlings rot or dry up. When the seedbed is moist, white cottony mycelium grows on the diseased parts and the nearby soil surface.
2. Disease Development Pattern
Damping-off is mainly caused by Pythium. The pathogen overwinters as oospores and mycelium in the soil or on diseased plant residues. It can survive in the soil for many years. When conditions are suitable, the pathogen germinates and directly invades from the base of gladiolus seedlings or enters through wounds.
The pathogen spreads through irrigation water, soil, manure and tools. The disease is severe when the soil temperature is 12-23°C. Therefore, low temperatures during the seedling stage will aggravate the severity of the disease. High humidity favors the germination and invasion of the pathogen. Insufficient nutrients, weak seedling growth, insufficient light and a low degree of lignification of the young stem make seedlings susceptible to the disease. In addition, improper sowing time, overly dense sowing, delayed pricking out and thinning, improper ventilation and watering, heavy clay soil, low-lying waterlogged terrain, application of compost containing diseased residues that has not been composted at high temperature, and continuous cropping will all aggravate the occurrence of damping-off.
3. Control Methods
(1) Prepare the seedbed well. Choose a plot with higher terrain, a lower groundwater table, good drainage, non-heavy soil, and no or few pathogens as the seedbed. Do not use old seedbed soil. The seedbed soil should be deeply plowed and finely leveled, and clean fertilizer should be applied.
(2) Disinfect the seedbed soil. Use formalin fumigation, that is, 3 weeks before sowing, rake the surface soil loose, apply 40 ml of the solution per square meter of seedbed, diluted 60-100 times (i.e., add 2400-4000 ml of water), spray it, and then cover tightly with plastic film. Remove the film after 1 week. Rake the soil loose to allow the chemical to fully volatilize. Sow after another 2 weeks. For soil disinfection, Wudai mixture can also be used, that is, quintozene and zineb mixed at 1:1, using 8-10 g of the mixture per square meter, mixed with 15 kg of fine soil to make medicated soil. When sowing, spread 1/3 of the medicated soil onto the seedbed or into the sowing furrow as a base layer, then use 2/3 of the medicated soil to cover the seeds, and finally cover with soil. After covering, sprinkle water on the soil surface and keep the soil moist regularly to avoid phytotoxicity. For disinfecting diseased soil, in addition to Wudai mixture, 50% carbendazim, or 50% thiram, or 50% thiophanate-methyl, or Wufu mixture (quintozene and thiram mixed at a 1:1 ratio) can also be used.
(3) Grow good seedlings. Carry out moderate pregermination. The sowing density should be appropriate. Flowers that prefer high temperatures and those that prefer low temperatures should be raised separately.
(4) Keep the seedling house warm and reduce humidity. Prevent cold wind from entering, and the temperature inside the house should be controlled at 20-30°C. The soil temperature should be maintained above 16°C. Seedbed management should avoid heavy watering. Pay attention to ventilation and air exchange to reduce humidity. Enhance light to promote seedling growth.
(5) Chemical control. In the early stage of the disease, spray 75% chlorothalonil wettable powder 600 times, or 64% oxadixyl-mancozeb wettable powder 300-500 times, or 25% metalaxyl wettable powder 600 times, or 40% fosetyl-aluminum wettable powder 300 times. Spraying should focus on the base of the young stems of the seedlings. Smoke fumigation with 45% chlorothalonil smoke agent can also be used. The dosage is 250 g per mu per treatment; after ignition, seal the seedling house for sterilization.
II. Gladiolus Gray Mold
1. Symptoms
This disease can damage leaves, peduncles, petals, stem bases and corms. In the early stage of leaf infection, rust-brown spots appear, which expand into nearly circular gray-brown or brown lesions. When moist, a gray mold layer forms on the lesions. In the early stage of peduncle infection, light brown water-soaked spots appear, which later expand and produce brown soft rot. Petals are susceptible; under cool and moist conditions, the petals become sticky and rot, with a gray mold layer forming on them. After stem base infection, stem rot occurs. When moist, the stem base becomes brown and soft-rotted, and the plant falls over and dies. Gray mold and sclerotia form on the diseased tissue. When the pathogen infects the corm, round brown spots appear and expand inward. This causes part or all of the center of the corm to rot, leaving only the outer skin. The corm may develop spongy rot, and black sclerotia can be seen after peeling off the outer skin.
2. Disease Development Pattern
It is mainly caused by Botrytis gladiolorum. The pathogen mainly overwinters through sclerotia. Cool climate and high humidity favor disease occurrence, and the disease develops rapidly when there are water droplets on the leaves and flowers.
3. Control Methods
(1) Horticultural management. Practice crop rotation when planting in the ground, and disinfect the potting soil when growing in pots; do not let the potting soil become too wet, and do not allow waterlogging when planting in the ground. Remove diseased plants promptly when found, remove old flower spikes, and burn them in a centralized manner.
Dig out the corms when the weather is dry, treat them at 30°C for 7-10 days, and store them after they are fully dry. During storage, control the temperature at -8°C and the relative humidity at about 70%.
(2) Seed corm treatment. Select disease-free corms as seed corms when planting. Treat seed corms suspected of being diseased with a chemical solution: at 46°C, place them in 50% procymidone wettable powder 1000 times solution for 20-30 minutes.
(3) Chemical control. In the early stage of the disease, spray 50% procymidone wettable powder 1000-1500 times, or 40% dimethachlon wettable powder 600 times, or 80% zineb wettable powder 600-800 times, or 50% dicloran 1000 times, once every 7-10 days, for 3-4 consecutive applications. 30% hydroxyisoxazole aqueous solution can also be used and drenched before and after planting.
III. Gladiolus Fusarium Wilt
1. Symptoms
Also known as dry rot. After infection, the growth of the diseased plant is stunted, and it wilts. Lesions on the corm mostly occur on the lower half. The lesions are light brown, water-soaked, and mostly irregular in shape. The lesions are sunken and shrink in a ring-like manner. During storage, the lesions expand and the corm rots. Based on differences in symptoms, this disease can be divided into the vascular discoloration type, the brown rot type and the basal plate dry rot type.
2. Disease Development Pattern
The main pathogen of Fusarium wilt is Fusarium oxysporum f. sp. gladioli. The pathogen is a soil inhabitant. It can survive in the soil for many years. It spreads through soil and diseased corms, invades from the root crown and expands to the entire plant. When conditions are suitable, the pathogen enters the vascular bundles and causes vascular discoloration. The disease occurs with continuous cropping, planting diseased corms and applying excessive nitrogen fertilizer. When stored in a cellar, if the corms are not fully dried and the storage period has high temperature and high humidity, all of these favor the occurrence of the disease.
3. Control Methods
(1) Strengthen cultivation management. The plot for planting gladiolus should have deep soil, rich organic matter and fertile soil. Apply sufficient organic fertilizer before planting.
Avoid continuous cropping on diseased soil, and it is best to implement a rotation system of more than 6 years; replace the cultivation soil, or disinfect the soil with chemicals or high temperature. For the disinfectant, 95% fenaminosulf soluble powder or 70% chlorothalonil soluble powder can be selected. Strengthen fertilizer and water management, and avoid excessive nitrogen fertilizer and soil waterlogging.
(2) Seed corm treatment. Select disease-free corms as seed corms. Disinfect the seed corms before planting. Soak them in 50% carbendazim wettable powder 500 times, or 64% oxadixyl-mancozeb wettable powder 400-500 times, for 30 minutes, and then dress the seeds with thiram. Alternatively, spray 1000 times solution of the antibiotic 401 on the surface of the seed corms, or soak them in 0.1% mercuric chloride aqueous solution for 3 minutes, then rinse with clean water, dry and plant.
(3) Treatment before storage. Harvest the corms on a sunny day. Avoid causing wounds when digging out the corms. Before storage, remove diseased corms and place the corms under dry conditions at 30°C. Treat for 10-15 days to promote wound healing and allow the corms to fully dry. During storage, control the temperature at 5-11°C and the relative humidity below 70%.
(4) Chemical control. In the early stage of the disease, spray 50% carbendazim wettable powder 500-1000 times, or 75% chlorothalonil wettable powder 800 times, or 70% thiophanate-methyl wettable powder 1000 times on the stem base, the soil near the stem base and the leaves, which can inhibit the spread of the disease.