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Citrus fruit serving
Citrus dragon disease is a devastating disease that seriously hampers the production and development of citrus. After citrus plants are infected with huanglongbing disease, the tree declines, the yield declines, the quality decreases, and the plant dies within 3 to 5 years, bringing immeasurable losses to the majority of orange farmers.
Citrus huanglong disease was first found in the Chaoshan area of Guangdong Province, China, and has a history of more than 100 years. In Guangdong, citrus yellow dragon disease has destroyed more than a million acres of citrus groves. With the great development of citrus production, the area of huanglongbing disease has been expanding, and the occurrence of huanglongbing disease has been confirmed in Guangxi, Fujian, Jiangxi, Hunan, Yunnan and Hainan.
Under natural conditions, yellow dragon disease harms almost all citrus cultivars. After citrus infection with huanglongbing disease, symptoms can be manifested throughout the year, with the most common occurrences in the field, followed by summer shoots and autumn shoots, followed by spring shoots. The symptom types of huanglongbing disease are complex and diverse, and through the unremitting efforts of many citrus researchers, a series of detection methods for huanglongbing disease have been developed.
First, the diagnostic technology of citrus yellow dragon disease
1. Diagnosis of the initial disease of huanglongbing disease
A few or more branches do not turn green, or stop turning green during the green turn, and the leaves show uniform yellowing. This uniform yellowing type of leaf is limited to the leaves on the new shoot, and the leaves of the basal branch below the new shoot are normal in appearance and do not have any lesions. This is one of the important features of the tree that first occurs from yellow dragon disease, called "yellow dragon".
2. The most typical symptom feature of huanglong disease trees - mottled
The main manifestations are that the leaves start from the base and near the lateral veins, gradually fade into yellow or light yellow, and continue to expand upwards and middle to form irregular macula, and the whole leaf leaves present uneven yellow and green asymmetrical patches.
3. Specific disease symptoms on diseased trees in the middle and late stages- yellow shoots with short, slender, zinc-deficient and manganese-like flowers and leaves are extracted (secondary symptoms)
4. Symptoms of "red nose fruit" appear
Orange fruits often appear dark red in the peduncle and cyan at the bottom when ripe.
Second, the causes of the spread of citrus dragon disease analysis
Citrus xanthosis is mainly transmitted by diseased scion, seedlings, and citrus wood lice. The main reasons for the spread of citrus dragon disease are as follows:
1. The breeding system of fine seedlings is not perfect, and fruit farmers plant seedlings with diseases.
For a long time, citrus seedlings are mainly individuals, most of the seedling bases are in unlicensed production, the base site selection and seedling production have not been in accordance with the "Citrus Seedling Origin Quarantine Regulations" to breed seedlings and apply for quarantine at the place of origin, resulting in a large number of diseased seedlings flowing into the market, the seedling disease rate is high, and the hidden dangers of disease after planting are large.
2. The understanding of the harm of yellow dragon disease is insufficient, and it is difficult to implement prevention and control measures.
Although the local authorities have also done a lot of science popularization and training work, most fruit farmers still lack knowledge of the identification and prevention and control of huanglongbing disease, and the harmful nature of the disease is mainly transmitted through psyllids in the field. Some fertilizer manufacturers even recommend fertilization treatment, resulting in missing the best prevention and control period, resulting in a large number of enrichment of field insect sources and disease sources, resulting in a situation of loss of control due to small losses.
3. Failed to prevent and control pyllids in time, and the disease spreads.
Citrus yellow dragon disease disease insect psychic lice is common, and the population is large (8 to 11 generations), strong reproductive ability (average laying 700 eggs / head), after obtaining the germ can be passed on for life, the prevention and control of citrus yellow dragon disease requires comprehensive control of citrus psyllids. Most of the farmers in China are small in scale and have a low degree of organization, making it difficult to form a conscious and effective joint prevention and control mechanism, and the spread of citrus dragon disease is difficult to control.
4. The bottleneck of scientific research has not yet been broken, and there is no effective treatment for huanglongbing disease.
Due to the in vitro cultivation of citrus huanglong disease bacteria so far, the study of their physical and chemical traits is insufficient, and it has not yet been able to screen out long-acting therapeutic agents and disease-resistant varieties; although there has been some progress in the study of disease-resistant varieties using transgenic technology, it is still far from production and application, and there is an anti-murmur. At present, there is no effective agent to cure the disease, citrus yellow dragon disease can only be prevented, can not be cured, the work is more difficult.
Third, the prevention and control measures of citrus yellow dragon disease
1. Cultivating disease-free seedlings is the basis for the prevention and control of citrus dragon disease
The disease-free nursery is not just a plastic mesh greenhouse, it is a disease-free nursery. Disease-free seedling breeding base, including several major parts of the construction:
(1) Where a rootstock seed garden is established, a garden shall be built in a place with good isolation conditions and excellent rootstock varieties shall be planted;
(2) Construct a library of disease-free good seed materials to preserve materials (seedlings) that have been detoxified and then identified to confirm that they do not have pathogens;
(3) Construct fully enclosed primary and secondary harvesting nurseries and build disease-free seedling breeding net sheds.
2. The prevention and control of citrus psyllids is the key to the prevention and control of citrus yellow dragon disease
Citrus wood lice generally overwinter as adults, and do not lay eggs without young shoots. Spring arrives, and overwintering adults migrate to the buds of the first spring of citrus to suck up sap and lay eggs. Therefore, the winter qingyuan is a key period of the year to control psyllids. The second is the initial stage of new shoots, and each new shoot stage, spraying at least 2 times, the first spray in the first bud about 0.5cm, 7 to 10 days apart spray the second agent.
3. Timely digging up diseased trees is the guarantee for the prevention and control of citrus yellow dragon disease
Principles for digging up diseased trees:
(1) If the young trees that have not borne fruit are sick, they will be dug up, dug up and then made up.
(2) If the newly fruited young trees born more than three years old are dug up in time if they occur in the spring shoot stage; if the disease occurs in the autumn shoot period, they are dug up after fruit picking and replanted with large seedlings;
(3) The old tree is sick, re-prune the diseased branches, and strengthen management; dig up the weak tree, and whether to replant after digging, according to the incidence of the orchard;
(4) Orchards with no disease or less disease should be strictly treated with diseased trees;
(5) Seriously ill orchards dig up diseased trees, generally do not replant;
(6) Planting reserve trees in case of digging up diseased trees and replanting them.
4. Strengthening cultivation management is necessary for the prevention and control of citrus huanglongbing disease
Earnestly implement the key measures for citrus cultivation and management.
It is necessary to control the summer shoots well, so that each new shoot can be neatly withdrawn, so that the unified spraying of drugs to prevent citrus lice. For fruit trees, controlling the summer shoots can not only preserve the fruit, but also destroy the food chain and spawning place of citrus psyllids, and also help prevent and control diseases and insect pests such as canker diseases and aphids.
There are many kinds of controlled shoot products on the market, and the majority of fruit farmers should give priority to the formal registration and high safety of the control products, so that their interests will be more secure.