Kiwi yellow leaf disease is a comprehensive disease caused by various diseases such as deficiency of the disease, root rot and nematode. In recent years, the kiwifruit in Xixia County has caused the whole plant to die due to the damage caused by yellow leaf disease, and the large-scale production reduction or even the harvest has become a major obstacle to the high quality and high yield of kiwifruit.
First, [onset characteristics]
(A) nematodes class Yellows county occurs mainly northern root-knot line coccidiosis and peanut root knot nematode, underground root nodules early birth, normal root bark color appearance, surface roughness greater tuberosity, post-knot The roots and the nearby roots are all rotten, turning dark brown, dissecting rotted nodules, showing milky white pear or lemon-shaped nematodes. After the plant is infected with nematodes, the upper part of the plant is short, the branches and leaves are yellow and weak, and the leaves and fruits are small and easy to fall. The pathogenic nematodes overwinter in the soil roots and insects inside and outside the insects. They can also be mixed with manure for wintering. The temperature rises in the next year, and the 2nd instar larvae invade from the root tip. The eggs are hatched in the soil for reinfection.
(2) Root rot yellow leaf disease root rot is a root-destroying fungal disease, and the pathogen is overwintered in the root and soil of the disease, and the disease occurs in high temperature and high humidity. The germs spread through tools, rain, water, and pests, and are invaded by lenticels and wounds. Mainly damage to the roots, causing the upper part of the plot to appear yellowing off the leaves, the tree body wilted and died.
(3) Deficiency of yellow leaf disease 1. Iron deficiency, light young leaves show pale yellow or yellowish white vein chlorosis, symptoms from the leaf edge to the main vein, the old leaves are normal, the younger leaves the young leaves So that all the leaves on the branches are green and yellow, and even the leaves are degraded or whitened. The leaves become thin and easy to fall off. The fruits are small and hard, and the skin is rough.
2. Magnesium deficiency, the symptoms appear on the old leaves, and the chlorotic spots are arranged along a certain distance along the leaf margin. The healthy green tissue on both sides of the main vein is wider, and the boundary between the green tissue and the healthy tissue is more obvious.
3. Zinc deficiency, the old leaves appear bright yellow veins chlorotic, the leaf margin is heavier, and the yellow veins between the old veins are more obvious. Sometimes the new shoots have small leaflets, and the small leaves show a narrow and long growth, which does not develop toward the width. Zinc deficiency not only affects the growth of the aboveground parts, but also affects the development of lateral roots.
Second, [incidence]
There are five kinds of serious cases: First, the old orchard entering the fruiting period is seriously ill due to the large load; the second is the past immersed land and the arid orchard that cannot be watered; the third is not paying attention to nitrogen, phosphorus, potassium and The orchard balances the supporting orchard; the fourth is to ignore the orchard that is responsible for the prevention of nematode disease and root rot; the fifth is to manage the extensive orchard. All of the above cases have fundamentally caused the tree to weaken, and the roots absorb and transport the ability to decline and yellow leaves occur.
Third, [pathogenesis]
Through the analysis of the onset symptoms and investigation status, there are many reasons for the kiwifruit yellow leaf disease in our county. First, the drought and water shortage in the orchard affects the nutrient absorption, followed by the large amount of fruit trees in the previous year, which makes the tree weak, resulting in yellow leaves caused by deficiency. disease. The deficiency is mainly due to the lack of iron, magnesium and zinc, especially iron deficiency. Once again, it is a hazard of nematode disease and root rot, which leads to a decrease in the ability of roots to absorb nutrients, causing the plants in the shoots to be short and the leaves to yellow and weak. Especially when there are three reasons for coexistence and mixing, it is more difficult to control.
Fourth, pollution-free prevention and control technology (a) nematode disease prevention and control 1. Strengthen seedling quarantine, do not allow the circulation of insects, do not plant with insects.
2. Use the anti-nematode wild kiwi species as the rootstock, such as soft jujube kiwi, and the nursery is not continuous.
3. Promote standardization and construction of the park, adopting (no pollution) standardization and scientific management from planting to unloading. For example, vigorously promote bio-organic fertilizer (0.5 to 1 kg per sapling, 1 to 2 kg per hole in the tree) to enhance the tree potential and improve the disease resistance of the tree.
4. Results The root-knot nematode was found to use 10% gram of phosphorus or ketan, 3% carbofuran granules, 3 ~ 5kg per acre, under the canopy, full shovel or deep turn, depth 5 ~ 50cm, harm Severe every 3 months.
5. Intercropping of low-stalk crops of grasses that are not infected with nematodes, such as green manure and pasture.
(2) Root rot prevention and control 1. Establish a drainage system to eliminate stagnant water.
2. Plant disease-free seedlings and use 100% DT suspension to soak the roots and roots for 3 hours.
3. The roots of the diseased plants were completely destroyed and the soil was fumigated with methyl bromide.
4. Use 90% crystal trichlorfon 150 to 30 times solution, add 5 kg of bran to trap underground pests.
5. Irrigation with 30% DT suspending agent 100 times solution according to 0.3kg/plant or 40% carbendazim fungicide 500 times solution 0.5kg/plant or 50% retort 800 times solution, at intervals of 15 to 20 days 1 time, even 2 to 3 times of irrigation is better.
(3) Prevention and treatment of deficiency syndrome 1. Combine pruning buds, thinning flowers and thinning fruits, cut off diseased vines, erase diseased weak buds, and reasonably leave flowers and fruits, so as to avoid excessive fruit load, causing tree weakness and reducing self-resistance ability.
2. Pay attention to balanced fertilization, combined with watering, in the application of nitrogen, phosphorus (phosphorus fertilizer should not be applied excessively) fertilizer, pay attention to the addition of potassium chloride or potassium sulfate, Shengguoyuan 7kg per acre. In the alkaline soil, ammonium sulfate, ammonium citrate, distiller's grains, vinegar grains and decomposed organic fertilizer, biological potassium, bio-organic fertilizer, etc. are added to enhance the tree potential and improve disease resistance.
3. Apply trace elements in soil, apply 1kg of ferrous sulfate per acre, 2kg of zinc sulfate, 1~2kg of magnesium sulfate or magnesium hydroxide.
4. Foliar application of trace elements of water-soluble fertilizer, spray with 0.2% ~ 0.4% of ferrous sulfate plus 0.3% zinc sulfate plus 0.3% ~ 0.5% magnesium sulfate spray every 7 to 10 days, even spray 2 to 3 times, the foliar spray effect before flowering is better.
In the orchard where the deficiency, nematode disease and root rot are mixed, the above three methods can be used simultaneously or crosswise to effectively control the occurrence of yellow leaf disease.
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