Kiwifruit root rot is a fungal disease caused by Basidiomycetes, Armillaria spp. and Phytophthora spp. Kiwi root rot is a devastating fungal disease that can cause the root neck and root system to rot, and in severe cases, the entire plant will die.
Occurrence pattern
The fungus has a wide range of hosts. The pathogen overwinters in the soil along with the diseased tissue. After the tree sprouts in the following spring, the pathogen spreads with farming or underground pest activities. It invades from root wounds or root tips, causing the root cortex tissue to rot and die, and can also enter the xylem. .
Characteristics and identification methods
At the initial stage, dark brown water-soaked lesions appear on the root neck, and gradually expand to produce white silk-like hyphae. The cortex and xylem of the diseased part gradually rotted and smelled of wine grains. After a large number of hyphae occurred, it took 8 to 9 days to form sclerotia, which were about the size of rapeseed and light yellow. The affected roots gradually turn black and rot, the above-ground leaves turn yellow and fall off, and the tree wilts and dies.
Use pesticides
(1) Desenzinc
Dosage: 40% WP
Control period: Carry out pesticide application on tree disks in the early stages, once every 15 days, and irrigate 2 to 3 times in a row.
Instructions: Use 37.5 grams of 40% WP, add 15 kilograms of water, dilute it to a 400-fold solution, stir evenly and irrigate the roots, and irrigate 2 kilograms of adult trees.
Precautions: It should be used in the early stage of the disease to achieve preventive effect; it cannot be mixed with copper preparations or alkaline drugs; safety precautions should be paid attention to when using medicine. Place it in a cool, dry and ventilated place. It will decompose when exposed to moisture and rain. Keep it away from food and feed, and out of reach of children.
(2)Carbendazim
Dosage: 50% WP
Control period: Spray twice before the onset of disease or in the early stages of the disease.
Instructions: Use 37.5 grams of 50% WP, add 15 kilograms of water, dilute it to a 400-fold solution, stir evenly and irrigate the roots, and irrigate 2 kilograms of adult trees.
Precautions: Carbendazim can be mixed with general fungicides, but when mixed with insecticides and acaricides, it should be mixed and used. It should not be mixed with alkaline agents. Long-term single use of carbendazim can easily cause bacteria to become resistant to antibiotics, so it should be used in rotation or mixed with other fungicides; when used for soil treatment, it is sometimes decomposed by soil microorganisms and reduces the efficacy of the drug. If the soil treatment effect is not satisfactory, other application methods can be used. The safety interval is 15 days.
(3)Bordeaux liquid
Dosage: 0.5% lime double basic copper sulfate.
Control period: When diseased plants appear in the field, use them alternately with thiophanate methyl and chlorothalonil, spray 3 to 4 times, with an interval of 7 to 10 days.
Instructions: Spray 0.5:1:100 Bordeaux mixture.
Precautions: This agent is a protective fungicide and should be sprayed before the onset of disease. It cannot be mixed with soap liquid, lime sulfur mixture, etc., nor can it be mixed with organophosphorus pesticides and genzine pesticides. This agent cannot be stored in metal containers to avoid corrosion. This agent should not be sprayed when it is damp or wet, otherwise copper ions will penetrate into the plant and cause serious damage. It should not be applied during the flowering period.
(4)Chlorothalonil
Dosage: 70% WP
Control period: When diseased plants appear in the field, use it alternately with thiophanate methyl and Bordeaux mixture, spray 3 to 4 times, with an interval of 7 to 10 days.
Instructions: Use 30 grams of 70% WP, mix with 15 kilograms of water, dilute to a 500-fold solution, stir evenly and spray.
Precautions: When applying pesticides, you should abide by the safe use of pesticides and wear protective clothing to prevent contamination of hands, face and skin. If there is contamination, wash it in time. Do not smoke, drink or eat during operation. Wash hands, face and exposed parts promptly after work; chlorothalonil is toxic to fish, so stay away from ponds, lakes, and streams when applying the pesticide. The remaining liquid medicine and the water used for cleaning medical equipment must not be poured into fish ponds and waters; chlorothalonil cannot be mixed with alkaline pesticides such as lime sulfur mixture and Bordeaux mixture; this product should be protected from moisture and sun, and stored in a cool, dry and ventilated place. It is strictly prohibited to mix with food, seeds and feed. Keep away from children. Waste packaging after use should be properly disposed of.
Dosage: 70% WP
Control period: When diseased plants appear in the field, use it alternately with chlorothalonil and Bordeaux mixture, spray 3 to 4 times, with an interval of 7 to 10 days.
Instructions: Use 15 grams of 70% wettable powder, mix with 15 kilograms of water, dilute to a 1000-fold solution, stir evenly and spray.
Precautions: It can be mixed with a variety of fungicides, acaricides, and insecticides, but it must be mixed and used immediately. It cannot be mixed with copper preparations and alkaline agents; if thiophanate methyl is used alone and continuously for a long time, the bacteria will develop drug resistance and reduce the control effect. It should be used in rotation with other agents. However, carbendazim, benomyl and thiophanate-methyl should not be used in rotation because there is cross-resistance between them; the agent can irritate the skin and eyes, and direct contact with the liquid should be avoided.
