Citrus scab disease, also known as citrus scabies, is a common disease in the spring planting management of citrus, is a fungal disease, mainly harmful to citrus new shoots, leaves and young fruits, the surface of the fruit "appearance" is seriously damaged, serious cases will cause fruit fall, if the prevention is not in place, will have a great impact on the yield and quality of citrus this year.
Warm and humid climate, for the occurrence of citrus scab is a very favorable condition, you grow citrus friends must pay attention to, grasp the key prevention and control nodes after the flower to the young fruit stage, reduce damage.
Scab disease on the fruit symptoms
Scab disease leaf symptoms
After the occurrence of citrus scab disease, it will lead to poor growth of citrus new shoots, and serious infestation will cause a large number of young fruits and young leaves to fall off, affecting tree potential and yield. Fruit that has not fallen off due to damage will also affect growth, the fruit is small and deformed, producing a large number of peel fruits and inferior fruits, reducing economic returns. Let's take a look at the scabs.
Leaf damage: At the beginning of the disease, oil-stained yellow dots are produced on the leaves, and then gradually expand, and the color becomes waxy yellow. Finally, the small spots of the disease gradually become tung and raised, and the leaf surface is concave and convex in the back of the leaf, and the dorsal part of the leaf protrudes into a conical scab, resembling a horn or funnel, and the surface is rough.
Young fruit victimization: the disease can occur shortly after the flowering, and the affected young fruit, the first brown spots, and then expand on the peel to form a yellow-brown cone, lignified nodular protrusions. After the victimization, the fruit does not develop normally, the fruit is small, the skin is thick, even deformed, and the taste becomes sour.
The lesions are small and dense, resembling moss; the diseased leaves are curled and deformed
The lesions are more independent, and in the later stage, one side is raised and the other side is concave, resembling a bull horn and a funnel
The petals fall off rapidly, and the young fruit has brown spots on the surface, which will fall off if the disease is more severe
The skin is thick, and the fruit surface is densely lignified with small moss-like spots, mostly striped or banded
The fruit surface is uneven, the lesions are large, and the convexity is often accompanied by lignification
1. Citrus scab disease, the pathogen is Citrus scab fungus, which belongs to the subphylum of semi-known bacteria, which can overwinter on the leaves, diseased shoots and fruits of citrus.
2. When the temperature is above 15 °C in spring and the humidity is suitable, conidia are generated from the original disease spots, and then spread by wind, rain and insects, and directly invade the new shoots, young leaves or young fruits through the epidermis and wounds.
3, pathogen cells can secrete scab cystic cavity mycelin, the compound can make the affected site produce a large number of reactive oxygen species, superoxide compounds, resulting in rapid death of citrus cells, so the incubation period after the occurrence of scabs infection is shorter, generally about 7 days can produce new spots.
4. The conidia produced by the new disease spots can infect citrus tissue again and continue to harm citrus.
1. Variety resistance:
Different citrus varieties have strong and weak resistance to citrus scabs. Generally speaking, oranges are the most susceptible to disease, Nanfeng oranges are more susceptible to disease, followed by citrus and grapefruit, and sweet oranges and citrus are more resistant to disease.
2. Maturity:
Citrus scab disease has the saying of "bullying the young and afraid of the old", can only infect the young tissue, germinating new shoots and young leaves, the fruit of the fruit after the flowering of the just seat is the most susceptible to disease, in the leaves, fruits quickly turn green and ripe, can greatly reduce the chance of disease.
3. Climatic conditions:
Suitable temperature and high humidity (there is a certain period of rainfall), which is an important condition for the outbreak of scabs, the general temperature is 15 ° C --28 ° C, it is easier to feel sick, which is the reason for the easy outbreak of citrus scab in spring.
4. Orchard environment:
Orchards with poor management, such as orchards with high planting density, poor ventilation and light transmission, and imperfect drainage and irrigation systems, are more likely to occur.
1. When building a new orchard, we must choose disease-free seedlings for planting;
2, winter pruning and garden cleaning medicine thoroughly in place, pay attention to pruning out of the diseased branches, diseased leaves, and take out of the garden to destroy, while the medicinal garden, you can use mineral oil, copper hydroxide and other whole garden spraying, clean up the wintering pathogen, reduce the pathogen base.
3. Strengthen water and fertilizer management, promote strong tree strength, and enhance disease resistance;
4. It is necessary to maximize the unity of the end, facilitate management, and reduce the probability of disease occurrence;
5. After the germination of the new shoots, the potassium dihydrogen phosphate + sodium nitrate fresh fat is sprayed in time after the leaf spread, so as to promote the rapid aging of the new shoots;
6. In the spring suitable period for scabs, we should pay attention to pharmacological prevention. In the three periods of spring budding, after flowering, and young fruit, if there is not much rain, it is recommended to use 80% Daisen manganese zinc wettable powder 500-750 times for prevention, if there are more rainy days, it is recommended to use 60% Daisen Lian•Pyrazole Ether Ester Water Dispersible Granules 750 times for prevention.
7. If citrus scab has occurred, it is recommended to use 25% phenylethicazole microemulsion 2000 times + 25% pyrazole ether ester suspension 2000 times control, and then prevent it. This program also protects against fungal diseases such as black star disease, macular disease, resin disease, and soot disease, and is safer for flowers and fruits.
8. For citrus scab disease, it should be cut off in time and treated centrally to prevent repeated infection.
Resources:
"China Plant Protection Pest Atlas and Control Treasure Book", editor-in-chief: Zhang Jianping;
"A new round of rain is coming, and fruit growers should beware of citrus scabs", agricultural assistant.