Occurrence and Integrated Control of Tulip Diseases

Tulip is a perennial bulbous herb belonging to the genus tulip of lily family, also known as lotus flower, grass musk, peony lily, etc. It is one of the cut flowers popular in the world. With the adjustment of industrial structure, tulip cut flower bases have been formed in many places in Jiangsu Province. However, in the production process, we found that every link may be damaged by fungi, bacteria, virus diseases, thus affecting the normal growth of plants, reducing the quality and ornamental of cut flowers, and serious damage will be caused. Therefore, preventing the occurrence and development of tulip diseases is the first problem to be considered by cut flower producers. The common diseases and their control methods in tulip production are described as follows.

1 Fungal disease symptoms and occurrence rules

1.1 brown spot

1.1.1 Symptoms mainly harm leaves, flowers and bulbs. The leaf spots were pale yellow at the beginning, round or oblong, slightly depressed, with dark water-stained edges, and enlarged at the later stage, turning gray brown. When the lesion occurs on the leaf margin, it causes the leaf to curl to one side. When the air humidity is high, the diseased part is covered with a large number of gray mold layers. After the perianth is dyed, it produces light brown spots, which gradually expand and turn dark brown, and finally wither. Flower buds cannot bloom when they are seriously infected. The disease spots on the stem are longer and deeper, and when they extend to one week of the stem, the upper part of the stem is lodging and rotten. Infected corms often have discolored, cracked outer skins and many small black-brown grains (sclerotia). Stripped skin, visible dark brown near round spots. The plants grown from the infected bulbs are dwarfed, yellowish green, and the flowers are withered.

1.1.2 Pathogenesis rule: Sclerotia overwinters in the remains of diseased plants or soil, and becomes the infection source in the following year. Germs are spread by rain and air currents. Rainy, foggy and dewy weather is conducive to the occurrence and spread of diseases. Plant planting too dense, poor ventilation or surrounding weeds, the disease is more serious. Plant growth is poor or damaged when also prone to disease.

1.2 Root rot

1.2.1 At the beginning of symptoms, the roots were translucent water-stained spots, which enlarged and caused the vascular bundle tissue to turn brown, causing root rot. Bulbs infected, bulb base around gray spots, brown edges, serious bulb soft rot. After planting bulbs with disease, some can not emerge, some can emerge, but poor growth, resulting in lack of seedlings broken ridge.

1.2.2 Pathogen is Pythium, which can survive in soil and infect host immediately. Water and humidity are favorable for the spread, infection and morbidity of bacteria.

1.3 Fusarium wilt

1.3.1 Symptoms of the disease bulb outside the scales appear dark brown and gray concave spots, and then expand into yellow brown or dark brown spots, such as the disease bulb in warm and humid places, white or pink hyphae and conidia will be born above, so that the infected tissue shrinks and hardens. After the bulb base is damaged, the rapidly developing disease spots can be spread all over the scales. Ethylene produced by the infected scales will cause the healthy bulb to produce glue phenomenon and affect the growth. The leaves on the bulb appear premature senescence, some leaves are erect and gradually become unique purple, the flowers grow thin, deformed, and even withered.

1.3.2 Pathogen overwinters in infected bulbs and soil by mycelium and chlamydospores, and planting infected bulbs often causes disease. In cultivation, the disease was easy to occur when the soil was wet and sticky, and the application of undecomposed organic fertilizer and nitrogen fertilizer was too much. When the occurrence of cutworm, beetle and root mite was more frequent, the disease of bulb damage was serious.

1.4 penicilliosis

1.4.1 Symptoms mainly damage bulbs, but also often show symptoms on the ground. Infected bulb primary dark brown pit spots, internal bulbs gradually rot, the last bulb into rotten wood dry rot. Sprouts and young leaves produce water-like spots, often covered with penicillium, the fruit body of pathogenic bacteria. The plants grown on the infected bulbs are short, chlorotic, do not bloom or have abnormal flowers, and the plants die prematurely.

1.4.2 Pathogen of the disease is Penicillium semi-know bacteria cluster penicillium, mainly saprobic, mostly from mechanical wounds, burns or mites caused by wound infection and the formation of harm. Cool environment is conducive to infection, bad ventilation and muggy storage places when the disease occurs rapidly. Bulbs are vulnerable during storage, bruised bulbs are most vulnerable.

2 Bacterial diseases

2.1 black rot

2.1.1 Symptoms mainly harm bulbs. Stem disk and stem surface, sometimes on the 2nd and 3rd scales, produce irregular black-brown spots at the beginning, and the surface is rough.

2.1.2 The disease is caused by Pseudomonas bacteria. The thallus is rod-shaped and has 1 - 3 flagella. The optimum temperature for the disease is 20~25℃, the lowest temperature is 5℃. The pathogen is in the infected bulb and soil, and the diseased body is the infectious source.

2.2 ulcer disease

2.2.1 Symptoms mainly damage leaves, pedicels and bulbs. After germination, the disease occurs when the first leaf unfolds, initially producing water-like silver-white spots on the leaves, and then the spots continue to expand, resulting in separation of epidermis and internal tissues. Bulb infected tissue cracking, scales brown, white spots appear on the outer scales, diseased scales piece by piece to fall off. At the later stage of storage, the disease spots raised and turned yellow. Pedicel disease produces pale yellow to brown canker spots, diseased plants dwarf.

2.2.2 Pathogenic bacteria overwintering in diseased tissues, and infected by contact with diseased parts in the following year when sprouts sprout. In open field cultivation, bacteria spilled from diseased tissues spread to adjacent plants by rain and rain sputtering. The optimum temperature for occurrence of the disease is 10℃, and the disease is more severe in rainy days in spring.

3 Viral diseases

3.1 color break

3.1.1 Symptoms of the disease leaves or petals can be shown, leaves are light green or gray spots, sometimes produce mosaic and mottled. Petal symptoms often vary slightly depending on the variety. In red or purple flower varieties, petals are pale yellow or white stripes of different sizes, which adds a bright landscape to the original healthy flowers, and the diseased flowers look better. In the past, some people mistakenly thought that this was a new variety, resulting in the widespread spread of the disease. In light or white flower varieties, because the petals themselves pigment less, symptoms are not obvious. At the same time, the species rapidly degenerated.

3.1.2 Tulip color breakage virus can be transmitted by sap, aphids and bulbs. Tulip aphids mainly transmit virus in bulb storage period, but not in growth period. Most varieties of bulbs imported from Holland in Shanghai and other places can only be planted for 2~3 years, and then gradually degenerate and become smaller, even unable to bloom. This virus is the main reason for degeneration.

3.2 necrosis disease

3.2.1 Symptom leaves, stems and petals produce spindle-shaped with purple edges or slightly white necrotic spots, so that leaves and flowers deformed. Infected plants die early and bulbs decrease.

3.2.2 The virus was originally tobacco necrosis virus and can be transmitted by inoculation of sap.

4 Integrated control

4.1 Seed ball and seed ball treatment

Choose disease-free bulbs with large diameter and large proportion, and eliminate diseased bulbs. Seed balls can be disinfected with 800 times solution of carbendazim and 1000 times solution of proparte, soaked for 20~30 minutes, dried, and sown on the second day. If there are conditions, warm soup can also be used to soak seeds, which has a better effect on killing pathogenic organisms, but it is necessary to master the temperature.

4.2 Enhanced soil treatment

Generally, it takes 2~3 years to rotate once. For fields with serious diseases, rotation for more than 3 years is an effective measure to prevent diseases and avoid planting tulips in soil contaminated by germs. The soil was disinfected by irrigating a mixture of 50 times formalin and 1000 times phoxim. After 7 days of film covering, the mixture was lifted and naturally air-dried (to avoid phytotoxicity to the seed balls). After 14 days, the seeds were planted again.

4.3 careful management

Care carefully to make it ventilated and transparent. In the shed, attention should be paid to reducing humidity, avoiding sprinkler irrigation, preventing water droplets from sputtering, and advocating the use of rain shelter cultivation methods. If the climate is dry, it is necessary to replenish water in time to facilitate root germination. Control the use of nitrogen fertilizer to avoid excessive application and promote the occurrence of diseases, and select nitrogen, phosphorus and potassium compound fertilizers. Fertilize in time at leaf opening stage. In bud stage, potassium dihydrogen phosphate can be sprayed on leaves for 1~2 times to ensure flowering quality. Fertilization to avoid fertilizer into the flower heart, resulting in rotten heart. The diseased leaves and flowers found in the growth period shall be cut off in time, and buried or burned in a centralized manner.

4.4 chemical control

Early detection and early prevention of any disease should be achieved. 70% Chlorothalonil WP or 50% Prochloraz WP or 70% Thiophanate-methyl WP 800~1000 times solution, 64% Sandufan WP 500 times solution or 50% Carbendazim WP 500 times solution were sprayed once every 7 days for 2~3 times continuously, and the control effect was good. To prevent fungicide resistance, alternate use of these pesticides. For bacterial diseases, 68% streptomycin powder 3000 times solution, 47% garinone WP 700 times solution and 30% succinone 500~600 times solution were sprayed once every 7~10 days before or at the initial stage of disease onset. For virus diseases, aphids should be controlled early to reduce the chance of virus transmission. 2.5% kungfu emulsifiable concentrate 3000~4000 times solution or 10% imidacloprid wettable powder 1.5g per mu should be used. If necessary, spray 500 times solution of 20% virus A wettable powder or 400 times solution of 5% Junduqing, or spray 1.5% Zhibingling 1000 times solution, spray once every 7 days, spray 3~4 times continuously.