A Detailed Guide to the Latest Control Methods for Corn Stalk Rot
There are many causes of stalk rot in corn production, and the most important category is fungal stalk rot. Fungal stalk and root rot is a type of disease caused by single or complex infection by various pathogens that leads to rotting of the root system and stem base, mainly caused by infection with Pythium, Colletotrichum, and Fusarium, and the symptoms shown on corn plants differ accordingly. Let us take a look below at the control methods for corn stalk rot!
Symptoms of the bacterial wilt type of stalk rot
The root system begins to develop disease at the grain-filling stage of corn, and the late milk stage to dough stage is the peak period of disease occurrence. From the first appearance of bacterial wilt leaves to the wilting of the whole plant generally takes 5 to 7 days; in fast-developing cases it takes only 1 to 3 days, while in long cases it can last more than 15 days. In the late milk stage, plants often suddenly wilt and die in patches, and because the dead plants remain blue-green, it is called bacterial wilt. The roots are affected first; initially the pathogen produces water-soaked light brown lesions on the fibrous roots, which gradually expand to the secondary roots until the entire root system becomes brown and rotted, and finally the thick and thin roots become hollow. The root cortex peels off easily and loosens, the fibrous roots and root hairs decrease, and the entire root system is easy to pull out. The disease gradually spreads to the stem base, and water-soaked spindle-shaped or long oval lesions begin to appear at the 1st to 2nd nodes of the stem base, then quickly soften and sink, becoming hollow and loose inside, collapsing at a pinch with an obvious feel. The internodes turn light brown, the ear husks dry green, the ear stalk is tough, the ear droops and is difficult to break off, the cob is soft, the kernels are shriveled, and threshing is difficult.
Symptoms of the bacterial type of stalk rot
The bacterial type of stalk rot mainly harms the middle leaves, stems, and leaf sheaths. When corn has 10 leaves, water-soaked rot appears on the leaf tips, the diseased tissue begins to soften, and a foul odor is given off. The lesions on the leaf sheaths are irregular in shape, with light reddish-brown edges, and the water-soaked area at the junction of diseased and healthy tissue is especially obvious. When humidity is high, the lesions rapidly expand upward and downward, and in severe cases the plant often breaks and falls above the diseased part 3 to 4 days after onset, exuding a yellow-brown foul-smelling bacterial fluid. The pathogen survives in the soil on diseased residues and invades the plant through stomata or wounds. High temperature and high humidity, and wounds caused by pest damage, lead to severe disease occurrence.
Transmission routes of corn stalk rot
The pathogen may overwinter in the soil on diseased residues, and the following year invades the plant through stomata or wounds. When corn is 60 cm tall, the tissue is tender and susceptible to disease, and wounds caused by pest damage favor pathogen invasion. In addition, pests carrying the pathogen also play a role in transmission and inoculation at the same time; for example, when populations of pests such as the Asian corn borer and cotton bollworm are large, the disease is severe. High temperature and high humidity favor disease occurrence; an average temperature of about 30°C and relative humidity above 70% is enough for disease occurrence, while an average temperature of 34°C and relative humidity of 80% leads to rapid spread. Low-lying areas or poor drainage, excessive density, poor ventilation, excessive application of nitrogen fertilizer, and many wounds lead to severe disease. Rotation, high-ridge cultivation, good drainage, and plots with an appropriate ratio of nitrogen, phosphorus, and potassium fertilizers produce robust plants and a low disease incidence.
Control methods for corn stalk rot
1. Select disease-resistant varieties: Planting disease-resistant varieties is the most economical and effective control measure, such as selecting varieties like Zhengdan 958, Nongda 108, Ludan 50, and Ludan 981.
2. Implement rotation to change crops: Planting corn continuously in the same plot for years can cause pathogens to accumulate in large amounts in the soil, and the disease will worsen year by year. If rotated with non-host crops such as soybean and peanut, the occurrence of the disease can be significantly reduced.
3. Strengthen field sanitation: After the corn harvest, promptly remove diseased plants and fallen leaves from the field and dispose of them in a centralized manner, which can greatly reduce the accumulation of pathogens and reduce sources of infection. Deep plowing of the soil during autumn plowing can also reduce and control sources of infection.
4. Use coated seeds: High-quality seed coatings contain fungicides, insecticides, and trace elements, which can both resist pathogen infection and promote seedling growth, enhancing disease resistance.
5. Strengthen cultivation management: Promptly carry out intertillage, hilling, and weeding to enhance the root system's absorption capacity; low-lying land should be drained to reduce field humidity and improve soil aeration, which helps reduce the occurrence of the disease.
6. Use chemical control: When sporadic diseased plants are found, metalaxyl 400-fold solution or carbendazim 500-fold solution can be sprayed on the roots and stems or used as a root drench, once every 7 to 10 days, for 2 to 3 consecutive treatments, with good therapeutic effect.