How to prevent and control maize rough dwarf disease? Detailed guide to symptom identification and medication methods

Maize rough dwarf disease is a viral disease of maize caused by Maize rough dwarf virus, commonly known as “dwarf maize” and “stunted maize,” and also called “maize cancer.” It is mainly transmitted in a persistent manner by viruliferous small brown planthoppers. So what are the symptoms of maize rough dwarf disease? How to prevent and control it? What medication should be sprayed?

Maize rough dwarf disease is a major disease during the maize seedling stage, severely affecting maize growth and reducing maize yield. It generally causes a 20%-30% yield reduction, and in severe cases up to more than 60%, or even total crop failure.

It is expected that maize rough dwarf disease will strike this year. Have you made prevention and control preparations in advance?

What symptoms do maize plants with rough dwarf disease show?

1. The growth of diseased plants is inhibited, with an average height of only a few dozen centimeters, shortened and thickened internodes, and severe dwarfing.

2. The root system of diseased plants is few and short, less than half that of healthy plants, and the plants are easily pulled out of the soil.

3. Diseased plants only grow leaves without jointing, and the leaves are densely clustered, short, and pointed.

4. The originally clear and smooth leaf veins also become intermittent and disorderly. As the disease progresses, obvious strip-like protrusions appear on the leaf veins on the underside of leaves and on leaf sheaths.

5. In mildly diseased plants, the tassel develops poorly and sheds little pollen, while the ear is short, with few silks and few kernels. In severely diseased plants, the tassel cannot emerge, or if it does emerge, it has very few branches and no pollen, and the ear is deformed and unfilled or has very few kernels.

Occurrence pattern of maize rough dwarf disease

Maize rough dwarf disease is a viral disease of maize caused by Maize rough dwarf virus (MRDV), transmitted in a persistent manner by small brown planthoppers. The nymphs or adults of the small brown planthopper overwinter under weeds at field edges and under wheat seedlings in fields, serving as the primary infection source for the following year.

The occurrence of maize rough dwarf disease depends largely on the field population of small brown planthoppers and the number of viruliferous individuals. Early-sown maize is more severely affected than late-sown maize. Maize near field edges, canal banks, and roadsides with abundant weeds is more severely affected, and maize near vegetable fields and other moist areas with abundant weeds is also more severely affected. There are certain differences in the degree of occurrence among different varieties.

Prevention and control measures for maize rough dwarf disease

Agricultural control

1. Depending on the situation, do not plant spring maize

In recent years, during years when maize rough dwarf disease is prevalent, if the cropping system is reformed, spring maize is not planted, and other crops are planted instead, the transmission route of the virus source can be cut off, which can promote the early disappearance of the disease.

2. Select disease-resistant varieties

This is the most economical and effective way to address the harm of maize rough dwarf disease. Different maize varieties have certain differences in resistance to rough dwarf disease.

3. Adjust the maize sowing date

Avoid the peak period of virus transmission by small brown planthoppers. Maize sown in early to mid-May, after emergence, coincides with the peak period of virus transmission by small brown planthoppers. In addition, maize is susceptible to the disease at the 3-5 leaf stage, so the incidence rate is highest.

Therefore, adjusting the sowing date can allow the seedling stage to avoid the peak period of virus transmission and reduce the degree of disease occurrence. Measures should be adapted to local conditions, implementing timely early sowing and early film-mulching for spring maize and timely late sowing for summer maize, and minimizing the planting area in severely affected areas.

4. Clear weeds

Gramineous weeds in fields, at field edges, and along ditches are intermediate hosts for virus transmission by small brown planthoppers. Before maize emergence, clear weeds at field edges, roadsides, and in ditches to reduce intermediate hosts, which can prevent small brown planthoppers from migrating to maize after emergence and causing damage, thereby reducing the virus source.

5. Strengthen field management

Strengthen field management during the maize seedling stage to promote early seedling growth, and pull out infected plants as soon as they are found. At the same time, water promptly to prevent drought from worsening the occurrence of the viral disease.

Chemical control

Chemical control should grasp 4 key periods and choose low-toxicity, high-efficiency pesticides for unified prevention and control to achieve good results.

(1) At the maize sowing stage, use seed coatings or maize seed dressings containing systemic insecticides to treat maize seeds, so as to repel small brown planthoppers and also achieve a relatively good control effect on seed-borne virus.

(2) In the early stage of wheat grain filling, which is the key period for controlling the young nymphs of the first generation of small brown planthoppers, timely grasp the development trend of small brown planthoppers at this time, and apply pesticides in a concentrated and unified manner during the peak period of young nymphs, using systemic pesticides such as imidacloprid (10 grams/mu) or buprofezin (50 grams/mu), and spray wheat fields and uncleared weeds at roadsides and in ditches. When spraying, pay attention to using sufficient water and spraying evenly and thoroughly to ensure insect control effectiveness.

(3) During the wheat maturity stage, because small brown planthoppers are attracted to tender green plants, at the end of May and beginning of June, after wheat matures, adults of the first generation of small brown planthoppers migrate in large numbers from wheat fields to surrounding spring maize fields, transferring to damage spring maize seedlings. At this time, maize seedlings at the 3-5 leaf stage are exactly at the susceptible sensitive stage. Therefore, the timing must be grasped well. In the early stage of small brown planthopper migration, apply pesticides in maize fields, using 50 grams of buprofezin per mu, or a mixture of imidacloprid (20-30 grams) and Virus A (50 grams) diluted with water for spraying, once every 3-5 days, spraying 3-4 times consecutively, which has a very good preventive effect on the disease.

(4) In the early stage of infection, 20 milliliters of 4.5% beta-cypermethrin can also be used, mixed with maize-specific liquid fertilizer and sprayed, which can effectively control the disease. The use of antiviral preparations must emphasize the word “early.” After the maize 5-leaf stage, its control and treatment effects become poor.