Control Methods for the Three Common Diseases of Pinellia
The three common diseases of Pinellia are: tuber rot, viral disease (leaf-curling disease), and damping-off (leaf-scald disease). These three diseases severely affect the planting returns of Pinellia, so how do these three diseases form? How should they be controlled? Let us introduce them below.
Pinellia tuber rot
Cause and symptoms: It occurs during high temperatures, the rainy season, prolonged excessive soil moisture, and the swelling period of tubers and bulbils. In the early stage when the pathogen infects the Pinellia tuber, irregular black spots appear around the edge of the tuber. These spots spread rapidly in all directions, and after 3-4 days, numerous pathogen spots join together and continue to infect the interior of the tuber. At this point, the Pinellia root system begins to shrink, and the aboveground leaves gradually turn from green to yellow and wither. After 1 week, the Pinellia tuber becomes round and blister-like, resembling overripe grapes, and the inside of the tuber is entirely black liquid; the whole plant dies, and finally only a thin outer skin remains. The spreading pathogen will rapidly infect other Pinellia tubers, causing the entire Pinellia plot to become infected and rot within a short period. Large tubers rot first, then it spreads to small tubers, and finally only bulbils smaller than 1cm remain. This disease is also currently the most common, difficult to treat, highly damaging, and widespread disease in cultivated Pinellia.
Control methods
1) Pay attention to selecting good varieties. For artificial cultivation of Pinellia, choose Pinellia 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 the seed stems before sowing. Soak the seeds in 50% carbendazim for 12 hours; soak the seeds in 5% plant ash solution for 2 hours; soak the seeds in 300-fold solution of 1 part 50% carbendazim + 1 part 40% phosethyl-Al for half an hour; soak the seeds separately in 300-fold vinegar and 50ml/liter potassium permanganate to prevent rot and increase yield.
3) Strictly select soil and terrain. The soil must be medium loam or loam to ensure good water filtration and aeration; the terrain should preferably have a slope of 10-25 degrees. If the terrain is flat, deeper and densely distributed seepage ditches must be dug.
4) During continuous rainy weather and when the soil is relatively moist, as long as you can enter the field for cultivation, carry out multiple forms and multiple rounds of intertillage and soil loosening to break the compacted layer of the soil, 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. Also promptly spray fungicides or broadcast 5kg/mu quicklime powder.
5) Promptly control the underground pests white grubs and cutworms. Use new pyrethroid pesticides containing 50g/l cyfluthrin EC, which has an activating effect, can drive pests out of their burrows to contact the pesticide, and quickly acts on the pest nervous system, causing poisoning and death. After large-scale field use in the last 2 years, the control effect has been 100%.
6) Emergency harvest of rotten stems. In the middle and late stages of Pinellia growth, if continuous rainy weather and relatively high soil moisture occur, frequently inspect the Pinellia growth conditions. If some Pinellia plants are found to have rot, regardless of whether it is the digging and harvest season, promptly and decisively harvest in time without delay; otherwise, the tubers will rot quickly, with the large ones rotting first and then the small ones, causing reduced yield or even total loss. While carrying out the emergency harvest, the Pinellia tubers dug 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 after 1-2 days, so do not be careless.
Pinellia viral disease (leaf-curling disease)
Cause and symptoms: This disease is caused by taro mosaic virus of the potato virus Y group. It is mainly due to virus carried in Pinellia seed stems or virus transmitted 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 occur. After the Pinellia plant becomes diseased, irregular yellow spots appear on normally growing leaves, causing the leaves to become mosaic, shriveled and distorted, curled upward, and the plant to become stunted and deformed with poor growth. This disease can also cause large amounts of rot in Pinellia during storage.
Control methods
1) Choose disease-free plots and regions for planting; strictly screen excellent Pinellia varieties.
2) Apply fermented and 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 emerges, continuously spray 1500-fold 40% dimethoate or 80% dichlorvos, once every 7 days, for 3 consecutive sprays.
5) In the early stage of disease, treat with new low-toxicity, low-residue agents such as Bingduqing, Keduwei, and Duba, once every 3 days, for 3 consecutive treatments.
Pinellia damping-off (leaf-scald disease)
Cause and symptoms: Among artificially cultivated Pinellia, this disease is one of the most common major diseases, and its cause is 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 transmission are poor, and the disease is severe. In the early stage of disease, green irregular lesions appear on the leaves and petioles, then the color of the lesions 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 develops rapidly and spreads quickly; once discovered, it spreads very fast, and treatment is troublesome. The soil and air of the entire plot give off a strong fishy odor.
Control methods
1) When selecting a plot, choose old vegetable land where the previous crop was not tomato, eggplant, cucumber, or Chinese cabbage, or a plot where the previous crop did not have damping-off, for planting Pinellia.
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 sunning 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 800-fold 75% chlorothalonil solution; 1000-fold 50% thiophanate-methyl solution; agricultural 200ppm streptomycin, Xinzhi streptomycin; 300ppm chloramphenicol; once every 7 days, alternately spray 3 times. Be sure to spray evenly, with no repeated spraying and no missed spraying.
5) Recently, trial spraying of 800-fold 66.5% Propamocarb and 500-fold 72% DuPont Curzate for control has also shown relatively good results.