Prevention and treatment of Actinidia root rot caused by soft rot leaves of root and neck cortex

Kiwifruit root rot is destructive, and its pathogen overwinters with the disease and residual tissue in the soil. After the tree sprouts in the spring of the following year, the pathogen spreads with the activities of tillage or underground pests, invading from the root wound or root tip, causing the root cortex tissue to rot and enter the xylem. The peak period of the disease is from July to August, during which the bacteria can be re-infected many times. After the diseased plant is infected, the tree is weak, the yield decreases, the quality becomes worse, and when it is serious, it will cause the whole plant to die.

Actinidia root rot

First, symptoms: kiwifruit can occur from seedling stage to adult stage, and the disease site is in the root. Root rot is caused by a variety of fungi, and the symptoms vary from pathogen to pathogen.

One is caused by Armillaria mellea. Disease symptoms: early kiwifruit root neck cortex appeared yellow brown water stains, cortex gradually blackened and soft rot, phloem and xylem part separated and easy to fall off, xylem also changed brown rot. In the upper part of the diseased plant, the new shoot is thin and weak, the leaf is small, the leaf color is light, and the growth is weak. When the soil moisture is high, the disease spot spreads rapidly, resulting in blackening and decay of the whole root system, rapid yellowing of leaves and wilting and death of the whole plant. In the flourishing period of fruit trees or after setting fruit, especially from July to August, if the rain suddenly clears up for a long time, or days of high temperature, the diseased plant will suddenly wilt and die. In the later stage, white hyphae could be seen in the diseased tissue, and many yellowish umbrella fruiting bodies were produced in the rotting roots.

The other is caused by Phytophthora, and there are two ways of infection: one is invading from the root tip, and then gradually developing to the interior; the other is invading from the root neck or graft, resulting in waterlogged spots, cortical necrosis and decay, and in severe cases, circular rot. The aboveground is weak, the bud is late, the leaf is small, the leaf color is yellow, when serious, the whole plant dies. White mildew is produced in the wet soil or in the peak period of the disease.

2. Conditions of onset:

Kiwifruit root rot is often related to soil porosity and PH value, planting depth and water and fertilizer management. According to the investigation, ① has heavy clay, dry and hard soil, poor permeability and poor root growth, so it is easy to be infected with this disease. ② beaches, such as the banks of Heihe River and Weihe River, have high groundwater level and serious stagnant water in rainy season. ③ white food soil is immature, hard and lack of organic matter, which is disadvantageous to the development of root system and easy to occur. In plots with too high ④ PH value, iron is fixed and cannot be absorbed normally, which leads to root rot. Improper watering and fertilization of ⑤ will damage the roots and easily induce root rot. When ⑥ is planted too deeply, root respiration is blocked, which can easily lead to root rot. The excessive amount of fruit hanging in ⑦ or the use of Daguoling in successive years lead to the weakening of tree potential, the decrease of resistance and easy to induce root rot.

3. Comprehensive control: cultivating disease-free seedlings, strengthening field management, timely removal of disease and residues in the field, elimination of underground pests, combined with chemical control, root rot can be effectively controlled or reduced.

(1) Agricultural prevention and control. Disease-free seedlings were cultured by ①, and kiwifruit seedlings were raised in disease-free areas where Gramineae plants had been planted for many years. Fertilization is mainly based on fully mature barnyard manure or cake fertilizer. In addition to the application of organic fertilizer, heavy clay is mixed with sand when there are conditions. In addition to increasing organic fertilizer, sandy soil is improved with heavy clay. When the PH value is greater than 8, it can not be cultivated, but it must be improved to make the PH value neutral or weakly acidic before cultivation. ② removes all plant remains from the soil when building a new garden. ③ kiwifruit needs water, is afraid of waterlogging and has weak moisture tolerance, so it is necessary to adopt reasonable irrigation methods in high temperature season, and avoid flood irrigation or tree disk irrigation, which can be introduced from canals respectively. If there are conditions, sprinkler irrigation or drip irrigation can be used, irrigation should be uniform, prevent stagnant water for too long, affecting root respiration. 4. For orchards with high groundwater level, low-lying terrain and poor drainage, ditches should be opened in time to drain water after a long period of rainfall or heavy rain, so as to reduce field humidity and increase soil permeability. 5. Reasonable planting depth. Kiwifruit has no main root, but the fibrous root is well developed. if it is planted too deeply, first, the respiration of the root system is blocked, the vitality decreases, and it is easy to be infected by bacteria; second, it is easy to let bacteria invade outside the graft interface. 6. Reasonable load. Some fruit trees are seriously overloaded due to leaving too much fruit or using Daguoling, which leads to the weakening of trees and the decline of resistance.

(2) Pesticide control. For infected adult orchards, 0.8% carbendazim 300 times or 40% carbendazim 400 times can be used to irrigate roots, and 3 kilograms of medicine solution per tree, once every 15 days, 3 times in a row, can inhibit root rot and increase the yield of kiwifruit per plant.