Integrated Control Methods for Taro Blight

Taro is one of the most common vegetables in our daily lives. It grows in the ground, wrapped in a fuzzy outer skin, and tastes very delicious. Moreover, the leaves of taro are rather distinctive, somewhat similar in appearance to lotus leaves.

What Is Taro

Taro is also called yu, yunai, or the underground corm of plants in the Araceae family. Its shape and flesh vary by variety, and the small taro is the type usually eaten. It is a perennial tuberous plant, often cultivated as an annual crop. The leaves are shield-shaped, and the petioles are long and thick, green or purplish-red; the base of the plant forms a shortened stem that gradually accumulates nutrients and enlarges into a fleshy corm, called "taro" or "mother taro," which may be spherical, oval, elliptical, or block-shaped.

Taro blight is a fungal disease. This disease generally occurs during the annual plum rain season and midsummer. Taro blight severely reduces taro yields, so when growing taro, special attention must be paid to controlling taro blight.

Symptoms of taro blight: it first occurs on the leaves, gradually spreads to the petioles and corms, and then rapidly expands and spreads, forming large concentric-ringed spots. If it occurs on the leaves, the concentric-ringed spots on the underside of the leaves are the most obvious, and the outer edge of the spots has conidia, appearing as white mold-like material. In severe cases, the diseased spots gradually rot and rupture, until only the main vein remains on the leaf, like a broken umbrella. If it occurs on the petiole, it often forms dark brown oblong diseased spots, causing the leaves and petioles to turn yellow and then wither. If it occurs on the corm, it causes the entire taro to rot and even be destroyed.

Integrated Control Methods for Taro Blight

When symptoms of taro blight appear, growers should go deep into the taro field for careful inspection. Once diseased spots are found, measures should be taken immediately to eliminate the disease in its initial stage and prevent the disease from expanding and spreading.

1. Agricultural control measures

① When planting, select disease-free taro seed corms;

② Implement crop rotation and strictly prohibit continuous cropping. The rotation period should be more than three years. Rotate with crops such as rice, corn, peanuts, and sugarcane;

③ Apply more phosphorus and potassium fertilizers and farmyard organic matter fertilizers to promote thicker and firmer tissue cells in the leaves and petioles and enhance the disease resistance of the plants. ④ Strengthen field management. During the rainy season, clear ditches and drain water in time to prevent waterlogging in the taro field.

2. Chemical control

Taro blight generally occurs mostly during the plum rain season and midsummer, especially during sun showers (also called "sun water"), and plants are most susceptible during midsummer with alternating sunny and rainy weather and high temperature and humidity. Once an infection center (plant) is found, apply chemicals immediately for control. The main chemicals are:

① Spray Bordeaux mixture. Its preparation method is: 0.5 kg each of copper sulfate, lime, and rosin, dissolve them with a small amount of clean water, mix them together, then add 75 kg of water and spray the whole field. Spray once every 7-8 days, for 2-3 consecutive sprays. The control effect can be above 90%;

② Drench plants with a 1000-fold dilution of Dexon, using 110 kg of liquid per mu, drenching once every 10-12 days, for 3-4 consecutive drenchings, which can effectively control the occurrence of the disease;

③ Mix 80 mL of Zhizhuangsu with 100 g of Topsin and dilute with 55 kg of water for spray control, with especially good results.

Taro Growing Conditions  

1. Temperature: Taro requires high-temperature and humid environmental conditions. A relatively large temperature difference between day and night is beneficial to corm formation. During the corm formation period, 28-30°C during the day and 18-20°C at night are most suitable.  

2. Water: Whether it is wetland taro or dryland taro, taro likes moist natural environmental conditions. Dryland taro requires moist soil during the growing period, while wetland taro requires a certain water layer during the growing period.  

3. Light: Taro is relatively tolerant of weak light and is not very strict about light intensity. It grows well under scattered light, and corm formation and expansion require short-day conditions.  

4. Soil: Wetland taro needs to be cultivated in paddy fields, low-lying land, or ditches. Although dryland taro can grow on dry land, it still retains the ecological type of a swamp plant, so moist areas should be chosen for planting.

Taro Cultivation Techniques  

1. Land preparation and fertilization: Taro has wide adaptability to soil, and fertile, deep, clayey soil with strong water retention is suitable. After the land is prepared, open furrows at a row spacing of 80-100 cm, with a furrow width of 50 cm and a depth of 35 cm, then fertilize inside the furrows. Taro has a high fertilizer requirement and a long growing period. First, apply sufficient base fertilizer: 2000 kg of high-quality organic fertilizer and 60 kg of 48% potassium sulfate compound fertilizer per mu, applied in furrows according to row spacing.  

2. Sowing method: Select seed taros free of pests, diseases, and wounds, spread them in the sun for 3-4 days, then arrange them closely indoors and cover them with 8-10 cm thick wet sand to promote sprouting, keeping the room temperature at 20-25°C. After 20-30 days, when the sprouts are 3-4 cm long and the 5 cm soil temperature is stable at 10°C, plant them. Open two seed rows on the bed, with a row spacing of 30 cm and a depth of 7 cm. After watering the furrows thoroughly, place the seed taros, with a plant spacing of 33-40 cm and 4500-5000 plants per mu.  

3. Watering management: Do not water before taro emerges. Keep the soil moist in the middle and later stages, and pay attention to drainage during the rainy season. Eighty days after emergence, combine watering with hole fertilization beside the plants. Taro is averse to dry soil; in drought, the leaves turn yellow and wither, but overly wet soil with standing water is also unfavorable for root growth. At the seedling stage, the soil should have sufficient bottom moisture, and watering should be strictly avoided. During the seedling stage, keep the soil alternately dry and moist, and pay attention to drainage when it rains.  

4. Intertillage and hilling: During the taro seedling stage, combine topdressing with intertillage to remove weeds and warm the soil. At the end of the seedling stage, carry out intertillage and level the cultivation furrows into flat ground. After that, hill up soil once about every 20 days, 7 cm thick, for a total of two times. The purpose of hilling is to inhibit the sprouting and growth of the apical buds of daughter taros and granddaughter taros, reduce nutrient consumption, allow the taro to fully expand and produce a large number of adventitious roots, and increase the drought resistance of the plants.  

5. Timely harvest: After taro matures, harvest it in time. In the Yangtze River basin, early-maturing varieties sown early are mostly harvested from early September to early October, while those sown late are mostly harvested from late September to late October, and mid-late maturing varieties are mostly harvested from the end of September to early November. According to market demand, harvest may be appropriately advanced or delayed, but generally it should be completed before heavy frost to prevent taro from freezing damage.  

6. Seed preservation method: For taro, choose a high-yield field with uniform growth for seed preservation, and select plants with the characteristics of that variety as seed plants. The seed corms should be harvested on a sunny day when the aboveground part has withered and yellowed and the daughter taros have fully grown. The size of seed taros is related to type. For the multi-daughter-taro type, 25-50 g is suitable, and at minimum it should be above 15 g. For the kui taro type, it should be above 25 g.

In rural areas, many pondsides are planted with taro, which shows that taro likes to grow in moist environments. In the process of growing taro, disease prevention is very important, because disease directly affects taro yield.