The main epidemic factors of Lily Diseases and the skills of Integrated Control

First, symptoms: on leaves, stems and bulbs. The leaves are susceptible to disease, causing them to wither. The initial leaf tip turns brown, the length 1-2mm, and then gradually aggravates, the disease spot expands into a nearly triangular, thinning, dry and withered shape, with cloud patterns on it. The length of disease spot is generally 17-28mm, the width is 5-8mm, the maximum length of disease spot is 56mm, the width is 12mm, and finally the leaves die, and some of them occur at the leaf edge, which is semi-oval brown disease spot, which can also lead to leaf death.

The disease spot on the buried part of the aboveground stem is brown dotted or longitudinally spotted, slightly sunken, causing the stem to collapse seriously. After the bulb is infected, there are many brown or black-brown nearly round or short strip-shaped or irregular spots on the outer scale, which are slightly sunken, and cause the scales to yellowing and, in severe cases, the bulbs rot. The above symptoms are often comprehensively manifested on the plant, that is, once the disease occurs, there are disease spots in the leaf withered, bulb and aboveground stem at the same time, and several pathogens can be isolated from the disease part at the same time, rather than one symptom caused by only one pathogen.

2. Pathogens: the diseased plants collected from the field have been identified by the Plant Protection Institute of Gansu Academy of Agricultural Sciences, there are four kinds:

1. Alternaria can be isolated from the stems, leaves and bulbs of lilies. 2. Alternaria, isolated from leaves. 3. Fusarium. 4. Rhizoctonia. 3 and 4 were separated from the stem. These pathogens overwintered on soil and plant residues and planting materials, and were the initial sources of lily diseases in the second year. Re-infection can be caused under suitable environment. It causes continuous disease, which is mainly spread by wind and rain and splashing of running water on the ground. In recent years, the pathogen jointly harmed the lily, causing comprehensive symptoms, resulting in the withering of the lily leaves, the yellowing of the bulb and the death of the whole plant.

Third, the main factors of disease epidemic

3.1, repeated cropping: in the lily planting area, the same piece of land is generally repeated for 5-7 years, and the elderly are more than 10 years, which provides conditions for the accumulation of germs in the soil, and is also an important basis for the epidemic of diseases. According to the investigation in Pingchang, Gan'an, Youhe, Wujiazhuang and other townships in the old producing areas, the rate of heavy stubble was 100%, the rate of diseased land was 10%, and the rate of diseased plants was 15,36%.

3.2. Wet damage: Lilium likes warm and dry climate and is suitable to grow on sandy soil. Now the planting area is an old rice area, and the soil is mainly paddy soil, which is easy to produce waterlogging damage. Waterlogging damage not only affects the normal growth of lily, reduces disease resistance, but also provides conditions for the invasion and development of bacteria, which has become the main factor for the prevalence of lily diseases. Four years' investigation found that the disease was prevalent in all Rain Water years, and the disease was serious in the fields with stagnant water.

3.3. Seed ball carrying bacteria: the lily provenances planted are generally selected from the lily bulbs in the current year. Because the field diseases have not been effectively controlled, most of the harvested bulbs carry bacteria, which provides the pathogen basis for the spread of lily diseases and the disease next year. We investigated in the newly developed lily planting areas, the seed carrying rate was 93%, and the disease rate reached 100% in the same year.

3.4, fertilizer damage: improper or excessive fertilization will cause premature yellowing and drying up of the lower leaves of the plant and reduce the disease resistance of lilies. Farmers are used to using ammonium bicarbonate as base fertilizer. Or use unrotten organic fertilizer such as pig manure and cow manure as base fertilizer, and the amount of fertilizer is about 300 kg / mu. Due to excessive fertilization, it not only affects the normal growth of lily, but also creates conditions for the invasion of bacteria.

3.5. Density: high density causes insufficient light in the lower part of the plant and poor air circulation in the field, which affects the normal growth and is conducive to bacterial infection. The row spacing of lily plants is 10cm × 13cm, with a discount of about 50 000 plants per mu.

3.6, density: the high density makes the lower part of the plant lack of light, which affects the normal growth of lily, the field is clouded, and the kiln circulation is poor, which affects the normal growth and is conducive to bacterial infection. The row spacing of 100 planting plants is 10 × 13cm, with a discount of 50 000 plants per mu.

IV. Prevention and control measures

4.1 Agricultural control: rotation: because some bacteria infecting lilies can survive in the soil for 2-3 years, lilies in seriously affected plots are stopped for 3-4 years, and generally diseased plots are stopped for 2-3 years. It is best to use flood-drought rotation. Do not rotate with crops of the same family.

Scientific fertilization and reasonable close planting: to create a favorable growth environment and improve its disease resistance is an effective way to prevent the occurrence of Baideng. In the aspect of fertilization, the base fertilizer is mainly used as phosphorus and potassium fertilizer and mature organic fertilizer, with little or no inorganic nitrogen fertilizer, 20 kg seed cake per mu for disease prevention, crushed and retted with water (about a week), and then mixed with 50 kg plant ash as base fertilizer. Reasonable close planting is recommended, with row spacing of 16.5 × 20cm or 13.2 × 25cm, that is, 2-25000 plants per mu, no more than 30 000 plants at most.

Get up the three ditches, change the wide box into the narrow box: when preparing the ground, you must start the three trenches well, and change the old habit of shallow trench wide box to deep trench narrow box, in order to facilitate drainage. Three trench standards: box groove width 30cm, deep 25cm, waist groove width 40cm, deep 30cm, perimeter groove width 50cm, deep 45cm, and trench slope, so that the rain stop ditch dry. The side of the box should be flat, changing the original width from 4 meters to 2.5 meters, and the field is too long to open a waist groove every 15 meters every 20 meters.

Removal of diseased body: some bacteria of lily disease can survive on the diseased body for more than 15 months, so it is necessary to remove the lily disease residue and burn it centrally during soil preparation, so as to reduce the initial infection of lily disease pathogen.

4.2 soil treatment: soil-borne fungi are the main miscellaneous bacteria causing lily diseases. Soil treatment can be carried out as follows: 50 quicklime per mu during soil preparation, and then ploughing, this method should be carried out 15 days before planting, or use 4000 times liquid of Luheng No. 1 to add constant Fumishuang, spray the seedlings and soil when the lily seedlings emerge.

4.3 kinds of ball treatment: the seed balls were selected before planting, the diseased scales were peeled off, and then immersed in the prepared solution for sterilization. Specific method: soak the seed ball in 40% formaldehyde 50 times solution for 15 minutes, rinse with clean water, and then sow. Or soak in 80% anthrax Fumei 500 times solution for 10 minutes or 70% methyl topiramate 1000 times solution for 10 minutes, then sow seeds immediately after rinsing with clean water, and the treated seed balls can not be stuffed or stored.

4.4 Field control: in the early stage of the disease in the field, use 80% anthrax Fumei 500x solution or 70% methyl topiramate 1000 fold solution, or 75% chlorothalonil 600x solution, or Luheng No. 1 4000 times liquid plus constant thiram spray, sprayed once every 5ml for 7 days, and sprayed for 3 times in a row, several fungicides can be used alternately, and the effect is better.