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Comprehensive prevention of corn rough dwarf
Maize rough dwarf disease is a viral infection caused by the Maize rough dwarf virus (MRDV). In recent years, this disease has shown a noticeable upward trend in certain regions of our province, becoming a significant threat to corn production and seriously affecting yield and quality. As the disease spreads, it poses a growing challenge for farmers and agricultural authorities alike.
The symptoms of the disease typically appear after infection. Infected plants show distorted leaves that are dark green, thick, and brittle, often forming dense clusters. On the back of the leaves, waxy white stripes may develop along the veins. In severe cases, seedlings may die or grow weakly, leading to significant crop losses. During the 3–5 leaf stage, the upper part of the plant becomes stunted, with clustered, bluish-green leaves. Most of these plants fail to tassel or produce ears, resulting in a major reduction in yield. When infected at the 5–7 leaf stage, the plants are also stunted, but some may still tassel. However, their economic yield remains low. In rare cases, late infections can result in short tassels that fail to cover the ears, or female ears that do not develop properly—this is a less common manifestation of the disease.
The occurrence of maize rough dwarf disease depends on three key factors: the presence of the virus, the presence of insect vectors, and the susceptibility of the corn variety. When the virus accumulates, there are sufficient vectors, and susceptible varieties are planted, an outbreak is likely. The population dynamics of the vectors, such as the small brown planthopper (Laodelphax striatellus), are influenced by climate, field management, and the growth stage of the crop. Similarly, the resistance of different corn varieties to the virus varies, and environmental conditions play a crucial role in determining the severity of the disease.
The amount of virus present in the environment is a critical factor. Grasses and weeds serve as alternative hosts for MRDV, so fields with poor weed control tend to have higher infection rates. Fields with heavy infestations of wheat dwarf virus, which is transmitted by the same vector, are particularly vulnerable. This highlights the importance of managing both crops and surrounding vegetation to reduce the risk of disease spread.
Sowing date also plays a key role. Early sown corn fields, especially those adjacent to weedy areas or located near orchards, tend to experience more severe outbreaks. The early growth stages of corn, particularly from emergence to the 7-leaf stage, are the most vulnerable. Delaying planting or adjusting sowing times to avoid peak vector activity can significantly reduce the risk of infection.
Weather conditions, especially during autumn and winter, influence the survival and population of the vector insects. Warmer winters lead to lower mortality rates among planthoppers, increasing their numbers and, consequently, the likelihood of disease transmission. This makes climate change a growing concern for the spread of the disease.
Currently, most commercial maize varieties are highly susceptible to the virus, with few resistant or highly resistant options available. This lack of genetic resistance makes the crop more vulnerable to outbreaks when vector populations increase.
To effectively manage the disease, a comprehensive approach combining cultural, biological, and chemical controls is essential. The main goal is to reduce the virus source and suppress the vector population, ensuring that corn avoids the most vulnerable growth stages.
First, selecting resistant varieties is important. While no fully resistant varieties are widely available, some cultivars, such as Zhengdan 958 and Qidan 20, show better resistance and should be used where possible. It is also advisable to avoid large-scale planting of a single variety to prevent widespread vulnerability.
Adjusting sowing times is another effective strategy. By avoiding planting during periods when the vector is active, farmers can reduce the chance of infection. Promoting the timely removal of wheat stubble and other weeds helps eliminate breeding grounds for the planthopper.
Weed control is crucial. Removing weeds from the field and destroying habitats suitable for the vector reduces the chances of virus transmission. Diseased plants should be removed and destroyed to prevent further spread.
Field management practices, such as proper fertilization and irrigation, help strengthen the crop’s health and resilience. A well-managed field promotes faster growth, reducing the time the plant is vulnerable to infection.
Chemical control measures include using insecticides to target the planthopper population. Seed treatments with insecticides like imidacloprid can protect young plants during the critical early stages. Spraying insecticides around the field and in nearby weeds can also reduce the risk of disease spread.
In the early stages of infection, applying antiviral agents such as 20% Virus A WP or 1.5% Dianzhi EC can help control the disease and improve outcomes. Consistent and thorough spraying is essential for maximum effectiveness.
By combining these strategies, farmers can significantly reduce the impact of maize rough dwarf disease and ensure more stable and productive corn yields.