What are the control methods for common tulip diseases?

Tulip, also known as "foreign lotus," is a bulbous flower of the lily family. It wins people's affection with its bright and rich flower colors, graceful flower posture, long flowering period, and wide variety of cultivars. However, in tulip production, various diseases often occur, which not only cause yield losses but also seriously affect ornamental value. Here we list several common diseases in tulip production and propose control measures combining cultivation management with chemical control.

1 Gray mold

1.1 Symptom identification

Mainly harms leaves, flowers and bulbs. After the leaves and flowers are affected, brown spots appear, most leaves and flower stalks rot, and the stems also become affected and rot. After the bulb is infected, the outer scales rot and many dark brown sclerotia are produced. In wet weather, a gray mold layer forms on the diseased parts. Plants growing from infected bulbs are dwarfed, yellow-green, and the flowers wither. This disease is a fungal disease, and the pathogen is. The pathogen overwinters as sclerotia in diseased plant residues or in the soil, becoming the infection source for the following year. The pathogen spreads through rain and airflow. Rainy, foggy and dewy high-humidity weather is favorable for the occurrence and spread of the disease. When plants are planted too densely, ventilation is poor, or weeds grow densely around them, the disease is more severe.

7.2 Control methods

① Practice crop rotation, renew the seedbed soil, or disinfect the soil before planting. Steam treatment at 70-80°C for more than 30 minutes can achieve the purpose of disinfection. Chemical agents can also be used for disinfection, that is, drench the soil with 1000-fold dilution of thiophanate-methyl, then seal it with plastic film for 7-10 days. Commonly used disinfectants also include benzimidazoles, benomyl, formaldehyde, etc. ② Carefully inspect the bulbs before planting, remove diseased bulbs, and disinfect the seed bulbs. The disinfection method is to soak the bulbs in 0.3%-0.4% copper sulfate or 2% formalin solution for 30 minutes, then wash with water, dry and plant. ③ During the growing period, promptly remove diseased flowers, diseased leaves and diseased plants, and destroy them centrally. ④ At the early stage of the disease, spray 50% benomyl 1000-fold dilution, 5% vinclozolin wettable powder 800-fold dilution, or 50% iprodione 1000-fold dilution. Spray once every 10 days, continuously 2-3 times.

2 Color-breaking disease

2.1 Symptom identification

Affected leaves show light green or gray-white streaks, sometimes forming a mosaic pattern. On red or purple varieties, color-breaking flowers are produced, and pale spots or streaks of varying sizes form on the petals. On varieties with pale or white flowers, the petal symptoms are not obvious, which is due to the lack of anthocyanins in the petals themselves. In severe cases, plant growth is poor. The pathogen is Tulip Breaking Virus (TulipBreakingVirus.), which overwinters and oversummers as sclerotia in bulbs and soil. During the growing period, it is transmitted by aphids, and the knives and scissors used when cutting flowers can also transmit it.

2.2 Control methods

① Select virus-free plants as propagation material. ② Promptly remove diseased plants. ③ Spray 40% dimethoate emulsifiable concentrate 1000-fold dilution, or 10% imidacloprid wettable powder 1000-fold dilution, or 2.5% derris extract 800-fold dilution to control aphids and cut off the transmission route. ④ When cutting flowers, the knives and scissors should be disinfected by heating or washed with detergent before use.

3 Southern blight

3.1 Symptom identification

The whole plant wilts, and white mycelial strands or rapeseed-like tea-brown small sclerotia wrap around the stem base, and the affected part turns brown and rots. A large number of white mycelial strands and tea-brown fungal bodies can be seen on the soil surface. The pathogen is, belonging to the Deuteromycotina fungi. The pathogen overwinters in the soil with diseased residues as sclerotia or mycelial strands. When conditions are suitable the following year, the sclerotia or mycelial strands produce hyphae for primary infection. The silky hyphae produced by diseased plants extend and contact neighboring plants or sclerotia, and spread through water flow for secondary infection, causing the disease to spread and expand. The disease is severe in continuous cropping, or in clay-heavy soil, low-lying terrain, or in years or seasons with high temperature and high humidity.

3.2 Control methods

① When diseased plants are found, promptly pull them out and burn them, and drench the diseased holes and neighboring plants with 5% validamycin aqueous solution 1000-1600-fold dilution, or 50% tian'an aqueous solution 500-600-fold dilution, or 90% dexon wettable powder 500-fold dilution, drenching 0.4-0.5 L per hole. ② When plowing, mix in 100-150 kg of lime powder per mu to make the soil slightly alkaline and inhibit the reproduction of the southern blight pathogen.

4 Mosaic disease

4.1 Symptom identification

Mosaic-like markings and chlorotic streaks appear on the leaves, sometimes necrotic spots occur, and dark spots form on the petals. Growth and development are inhibited. When symptoms are severe, the bulbs do not grow large, and the damage is great. The pathogen is Cucumber Mosaic Virus (CMV). This virus spreads through the sap of diseased plants, and aphids are the vector for virus transmission.

4.2 Control methods

① Remove diseased plants and burn them promptly. ② Use virus-free healthy bulbs as propagation material. ③ Use 40% dimethoate emulsifiable concentrate 1000-fold dilution, or 10% imidacloprid wettable powder 1000-fold dilution, or 2.5% derris extract 800-fold dilution to control aphids.

5 Brown spot

5.1 Symptom identification

It harms tulip leaves and flowers, causing leaves and flower stalks to rot. The lesions are light gray with brown edges. When affected at the seedling stage, the plants often bend and finally die. Under humid conditions, a gray mold layer, namely conidia, is produced on the diseased parts. When bulbs are affected, the whole plant is dwarfed, the stem base and outer scales of the bulb rot, and many light black or dark brown sclerotia are produced. The pathogen is Botrytis tulipae, commonly found in tulip cultivation areas, and is more severe in the rainy season. High air humidity is the main condition for the occurrence and spread of the disease. It overwinters as mycelium and sclerotia remaining in rotten bulbs and soil.

5.2 Control methods

① Remove diseased bulbs before planting, and soak the seed bulbs in 0.3%-0.4% copper sulfate or 2% formalin solution for 30 minutes. ② During the growing period, promptly remove diseased leaves and diseased flowers and destroy them centrally. ③ Once buds or flower buds showing symptoms of this disease are found, remove them immediately to control the development of the disease. ④ At the early stage of the disease during the growing period, spray 50% iprodione 1000-fold dilution, or 50% procymidone 2000-fold dilution, or 50% duomeiling 1000-fold dilution. Spray once every 10-15 days, continuously 3-4 times.

6 Basal rot

6.1 Symptom identification

It belongs to the genus Fusarium, order Moniliales, class Deuteromycotina, and mainly harms seed bulbs. After seed bulbs are affected during the growing period, the leaves turn yellow and wilt, the root system is sparse, and water-soaked blue-gray wet rot appears at the base of the bulb. The rotten tissue has a pungent distiller's grains smell, and after drying the lesions appear gray-white and lime-like. During bulb storage, the main manifestation is gum exudation, followed by yellow-brown dry rot. The pathogen is Fusarium oxysporum f. sp. tulipae. The pathogen overwinters in infected bulbs and soil. High temperature at the production site and poor ventilation during storage are the main conditions for the occurrence and epidemic of the disease.

6.2 Control methods

① Appropriately delay planting and dig up bulbs early to avoid the high-temperature period as much as possible, so as to prevent damage by the pathogen. ② Healthy bulbs and diseased bulbs should be stored separately in a ventilated and cool place (below 15°C). ③ Do not plant too densely, and promptly remove diseased plants found during the growing period. ④ Within 48 hours after digging out the bulbs, soak them in 50% benomyl wettable powder 2000-fold aqueous solution for 15-30 minutes, dry them, and then store them. ⑤ Select disease-free seed bulbs and implement a 3-year rotation system.