How to prevent and control common diseases in the middle and late stages of Pinellia ternata growth
Tuber rot disease
1. Causes and symptoms
Occurs during high temperatures, the rainy season, prolonged excessive soil moisture, and the swelling period of tubers and bulbils. In the early stage of the pathogen infecting Pinellia ternata tubers, irregular black spots appear around the edges of the tubers, and these spots rapidly spread outward. After 3-4 days, numerous pathogen spots merge together and continue to infect the interior of the tuber. At this point, the root system of Pinellia ternata begins to shrink, and the above-ground leaves gradually turn from green to yellow and wither. After 1 week, the Pinellia ternata tubers become round and blister-like, resembling ripe grapes, and the interior of the tubers is entirely black liquid. The entire plant dies, and finally only a thin outer skin remains. The spreading pathogen rapidly infects other Pinellia ternata tubers, causing the entire Pinellia ternata plot to become infected and rot within a short period. Large tubers rot first, then the rot spreads to small tubers, and finally only bulbils smaller than 1 cm remain. This disease is also currently the most common, difficult to treat, most harmful, and widest-ranging disease in artificial cultivation of Pinellia ternata.
2. Prevention and control methods
(1) Pay attention to selecting good varieties. For artificial cultivation of Pinellia ternata, choose varieties with strong disease resistance and vigorous growth, such as excellent varieties with leaf shapes like "narrow three-leaf" and "willow-leaf shape."
(2) Disinfect seed tubers before sowing. Soak seeds with 50% carbendazim for 12 hours; soak seeds with 5% plant ash solution for 2 hours; soak seeds with a solution of 1 part 50% carbendazim + 1 part 40% phosethyl-Al at 300 times dilution for half an hour; soak seeds separately with 300 times vinegar and 50 ml/L potassium permanganate to prevent rot disease and increase yield.
(3) Strictly select soil and terrain. The soil must be medium loam or loam, ensuring good water filtration and air permeability; the terrain should preferably have a slope of 10-25 degrees. If the terrain is flat, deeper and densely distributed drainage ditches must be dug.
(4) During continuous rainy weather and when the soil is relatively moist, as long as it is possible to enter the field for cultivation, carry out multiple forms and multiple rounds of intertillage and soil loosening to break the compacted soil layer, allow harmful gases in the soil to escape, allow fresh oxygen from the air to enter, and increase gas exchange between the soil and the air. This measure can effectively prevent and reduce the occurrence of rot disease. Also promptly spray fungicides or broadcast 5 kg/mu of quicklime powder.
(5) Promptly control underground pests such as white grubs and cutworms. Use new-type pyrethroid pesticides containing 50 g/L cyfluthrin EC, which has an activating effect, can drive pests out of their burrows to come into contact with the pesticide, and rapidly acts on the pest's nervous system, causing poisoning and death. After large-scale field use in the last 2 years, the control effect was 100%.
(6) Emergency harvest when stems rot. In the middle and late stages of Pinellia ternata growth, if continuous rainy weather and relatively high soil moisture occur, frequently check the growth of Pinellia ternata. If some Pinellia ternata plants are found to have rot disease, under such circumstances, regardless of whether it is the harvesting season, promptly and decisively carry out an emergency harvest without delay. Otherwise, the tubers will rot very quickly, with large ones rotting first and small ones afterward, causing reduced yield or even total loss. While carrying out the emergency harvest, the Pinellia ternata tubers dug out from the wet mud should immediately be peeled and processed, because at this time the fresh tubers are still rotting internally. If not processed, most tubers will still rot away after 1-2 days. Do not be careless.
Viral disease (leaf curl disease)
1. Causes and symptoms
This disease is taro mosaic virus of the potato virus Y group.
It is mainly caused by virus carried in Pinellia ternata seed tubers or by transmission by insects such as aphids. It mostly occurs and spreads in early summer, under high temperature and rainy conditions, and when aphids and other insects appear. After Pinellia ternata plants become diseased, irregular yellow spots appear on normally growing leaves, causing the leaves to become mosaic-patterned, shrunken and distorted, curling upward, with the plant becoming dwarfed and deformed and growing poorly. This disease can also cause large amounts of rot in Pinellia ternata during storage.
2. Prevention and control methods
(1) Choose disease-free plots and regions for planting; strictly screen improved Pinellia ternata varieties.
(2) Apply fermented and thoroughly decomposed organic fertilizer, and appropriately apply additional phosphorus and potassium fertilizer.
(3) Promptly and thoroughly eliminate or prevent the occurrence and spread of pests such as aphids.
(4) After Pinellia ternata emerges, continuously spray 40% dimethoate or 80% dichlorvos at 1500 times dilution, once every 7 days, for 3 consecutive sprays.
(5) In the early stage of disease onset, treat with new-type low-toxicity and low-residue agents such as Bingduqing, Keduwei, and Duba, once every 3 days, for 3 consecutive treatments.
Damping-off disease (leaf scald disease)
1. Causes and symptoms
This disease is one of the most common major diseases in artificial cultivation of Pinellia ternata, and its causes are still being studied and observed. It is most likely to occur under high-temperature rainy seasons and high-humidity environmental conditions, especially when ventilation and light penetration are poor, and the disease is severe. In the early stage of onset, green irregular lesions appear on leaves and petioles, and the color of the lesions then deepens, the affected parts soften, and the leaves droop in a semi-transparent state as if scalded by boiling water, sticking to each other. This disease has an acute onset and spreads quickly. Once discovered, it rapidly spreads, and treatment is troublesome. The soil and air of the entire plot give off a very strong fishy, foul odor.
2. Prevention and control methods
(1) When selecting a plot, choose old vegetable land where tomatoes, eggplants, cucumbers, or Chinese cabbage have not been previously planted, or plots where the previous crop has not had damping-off disease, for planting Pinellia ternata.
(2) During the rainy season and high-temperature season, attention should be paid to reducing soil moisture.
(3) After the soil is selected, carry out winter plowing and sun-drying of soil clods in winter. Do not apply undecomposed fertilizer, and appropriately apply or do not apply nitrogen fertilizer among chemical fertilizers.
(4) Prevention first. After high temperature and rain before disease onset, use 75% chlorothalonil at 800 times dilution; 50% thiophanate-methyl at 1000 times dilution; agricultural 200 ppm streptomycin, new phytomycin; 300 ppm chloramphenicol; once every 7 days, alternating sprays for 3 times. Note that the pesticide must be sprayed evenly, ensuring no repeated spraying and no missed spraying.
(5) Recently, trials using 66.5% propamocarb at 800 times dilution and 72% DuPont Curzate at 500 times dilution for spray control have also shown relatively good results.