Sichuan citrus foot rot comprehensive control technology

Sichuan citrus foot rot comprehensive control technology

Li Zhengfu and others

In the 1970s and 1980s, various counties in the Nanchong area set up citrus production offices to vigorously develop citrus production. Due to the rapid development, the rootstock of the grafted seedlings has not been selected, the grafting site is too low, the planting is too deep, the soil is not improved, the drainage is not smooth, the humidity of the orchard is too large; neglect management, the tianniu and the gilding insect are seriously harmful, the crops are closer to the tree, and the mechanical injury is caused by man, causing the invasion of the bacteria, resulting in serious foot rot disease. The orchards built in the counties of Nanchong are destroyed in seven or eight years with good results, and it is difficult to exceed 10 years, and the poor results are destroyed in five or six years, almost one piece of construction is destroyed, which seriously affects the development of citrus in Nanchong. At present, nanchong city in the yangtze river citrus belt, to develop late ripening citrus as the goal, late ripening citrus planting area reached 86,700 hm2, output of 680,000 t, has become one of the main economic sources of agricultural income in Nanchong. In order to prevent the impact of citrus foot rot on the citrus industry in Nanchong, the pathogenesis characteristics and prevention techniques are introduced as follows.

1 Influencing factors

High temperature and humidity are the main factors affecting the occurrence of citrus foot rot. From May to September, the temperature in the citrus producing area rises to more than 20 °C and the rain increases, which is the main period for the onset of citrus foot rot. During this period, as the temperature rises, the foot rot bacteria begin to be active, the germs invade the wounds on the neck of the citrus root caused by agricultural activities, tianniu, gidding insects and other pests with rainwater, and the disease spots that have invaded continue to expand until the wound overflows, causing water and nutrient transportation to be blocked, the root system is stopped, the leaves are yellow, deformed, the fruit becomes small, premature, shedding, the taste is sour and light, which seriously affects the commerciality of the fruit, resulting in yield reduction, the overall death of the plant, the destruction of the orchard, and the impact on the production enthusiasm of the fruit farmers.

2 Harmful symptoms

Citrus foot rot is a fungal disease of the root neck of the citrus tree, which can also be harmful to the lower fruit of the canopy. At the beginning of the disease, the bark of the diseased part is water-stained, has a lees smell, and the color turns brown and often oozes brown glue. When the climate is dry, the spots dry and crack. When warm and humid, the diseased part continues to expand vertically and horizontally, down to the root, and generally spreads upwards to no more than 30 cm from the ground, expanding horizontally, causing annular overflow. The midribs and lateral veins of some of the large branches of the diseased tree or the entire canopy leaves are yellow, causing the leaves to fall, the branches to wither, the tree to weaken, the flowering is more, the flowering period is short, the fruit is less fruitful, the fruit is colored early, and the skin is coarse and sour. When the fruit is onset, it first has a round pale brown lesion, and then gradually becomes a brown water stain. The healthy part of the disease is obvious, only infecting the white cortex, not rotting and pulp. When dry, the spots are dry and tough, and the fingers are slightly elastic when pressed; when wet, they are water-stained and soft, growing white hyphae and have a putrid odor. The fruit, which is severely ill, falls off soon.

3 Route of transmission and pathogenesis

Pathogens overwinter in mycelium and thick spores in diseased strains and in diseased remnants in the soil. As temperatures rise the following year and rainfall increases, the hyphae in old plaques continue to harm healthy tissues, while sporangia are constantly forming, releasing zoospores, spreading with water or soil, infecting new plants from wounds. It can also be splashed with raindrops on the fruit near the ground, causing the fruit to become ill. The disease resistance of different citrus varies significantly. Among them, citrus aurantium, citrus aurantium, citrus aurantium, citrus aurantium, lime and grapefruit are highly resistant to diseases; fragrant orange, Yichang orange, red-skinned mountain orange, lime, red lemon, coarse lemon are medium; sweet orange, lime, kumquat, yulik lemon and other more susceptible to diseases. High temperature and rain, waterlogging; low-lying orchards, heavy soil, poor drainage; orange trees planted too deep, too dense or interplanted high-stalk crops; gidding insects, tianniu and other pests and other causes such as mechanical damage during labor, so that the base of the tree has a wound; the fruit hanging under, close to the ground, etc. are conducive to the occurrence of this disease.

4 Integrated control techniques

[Jishan Huayao self-media network debut] the use of disease-resistant rootstock. The selection of citrus aurantium, red orange, goji orange, lime and other disease-resistant rootstocks, improve the grafting site, the general grafting interface should be more than 20 cm from the ground, is the most cost-effective way to prevent and treat foot rot.

Shallow planting, reasonable dense planting, rational orchard drainage system, elimination of intercropping tall crops, and reduction of orchard humidity are effective measures to prevent foot rot.

By replacing the anvil. For fruit trees with excellent varieties and in the full fruit stage, plants that have been infected with foot rot, plant 3 disease-resistant rootstocks, red oranges, etc. at the base of the main trunk, which are distributed in a triangular shape, and the anvils are exchanged, which is the main measure to treat the diseased plants.

Strengthen cultivation management. Doing a good job in draining orchards and reducing the humidity of orchards; timely preventing and controlling tree trunk pests—— — the pests and man-made wounds of tianniu and gidding insects; strengthening fertilizer management, increasing the application of organic fertilizers and phosphorus and potassium fertilizers, improving the soil, strengthening the tree potential, and not causing the opportunity for invasion of germs are the key measures to prevent foot rot.

chemical control. Once it is found that the plants in the orchard have water-stained spots, scrape the spots to 1 to 2 cm of healthy tissue in time, and burn them centrally, and then apply Guoguang production "843" kang fusing agent 10 times liquid, 25% toxin mold 100 times liquid, stone sulfur compound residue and other sterilization at the spot, it is best to apply fresh cow dung to ensure the efficacy.