Symptoms of corn rough dwarf
The crude corn virions are spherical and have a passivation temperature of 800C. They can survive for up to 37 days at 20°C. The virus is transmitted by insects. The main insect is Laodelphax striatellus, which is a persistent virus. The incubation period is 15-20 days. It can also infect wheat (disease caused by orchid dwarf), oats, millet, sorghum, valerian and so on.
1. Symptoms: The corn can be infected during the entire growth period, with the most severe disease at the seedling stage, with symptoms ranging from 5 to 6 leaves. The transparent, oil-immersed, whitish dotted lines appear on both sides of the base of the heart and midrib. Gradually expand the entire blade. The diseased seedlings were dark green, and the leaves were stiff, short and thick, and the heart was unable to expand properly. The growth of the diseased plants was stunted, and waxy white uplifted stripes were found on the veins on the back of the dwarfing leaves. Dark green leaves, short internodes, top leaves clustered like Clivia. Leaf veins, leaf sheaths, and temporal lobes have waxy white sticks on the veins of the leaves, showing a noticeable roughness. From the 9th to the 10th leaf stage, the dwarfing phenomenon of the diseased plants was even more pronounced. The upper internodes were short and swollen, and the top leaves were clustered. The diseased plants were less than half the height of the healthy plants, and most of them were not able to produce heading and fruiting. Although some tassels could be extracted, Very few branches, no pollen. Ears are misshapen, with few filaments, severe dwarfing of plants, degeneration of tassels, and abnormal ear formation.
2. Hazard: Since 1993, the incidence of corn rough dwarf disease has increased significantly, causing great losses to the city's corn production. When the disease occurred in 1996, the average diseased field strain rate reached 40%, and the average yield was reduced by 10% to 30%. 2007-2009 occurred in the Huanghuai region for three consecutive years. How to control corn virus disease, especially the damage of maize rough dwarf disease (MRDV), has become a very practical issue. Therefore, we have conducted a systematic survey of maize rough dwarf disease in recent years. The study found that: 85.16% of the maize plants in the diseased plant sample were almost always or never produced, the plant height was only 1/2 of that of the healthy plant, and there was no grain in the ear or ear; 98.44% of the plants had a loss rate of grain weight. above 50.
3. Characteristics: In northern China, the dwindling virus winters in winter wheat and other weeds. It can also live in the body of poisonous insects. After the corn was unearthed in the second year, the virus was transmitted to corn seedlings or sorghum, millet, and weeds through transmission of poisonous insects, and was transferred to harm. The corn is susceptible to disease before the 5th leaf stage, and the resistance increases after the 10th leaf stage, and it is light even if it is affected. The emergence of corn to five ten-phase if the encounter with the transfer of poisonous insect migration peak, the incidence is serious, so the sowing date and the severity of the disease closely related to corn, such as Hebei Province in mid-May sowing corn, seedling stage is met with the first generation, gray The adult fleas of locusts have a severe onset. Extensive field management, more weeds, more fly plover and heavy disease.
Control method of corn rough dwarf
1. Agricultural control methods
In the prevention and control of corn rough dwarf diseases, we must adhere to the principle of comprehensive prevention and control based on agricultural control and supplemented by chemical control. Its core is to control the source of poison, reduce the source of insects, and avoid hazards:
1 Strengthen monitoring and forecasting: Focusing on regularly locating and regularly surveying the disease severity and disease severity of wheat, field weeds, and corn in disease-prone areas, we also investigated the occurrence density and the rate of poisoning of Laodelphax striatellus. Before and after the end of autumn and late spring and corn planting, based on the wintering base and the rate of disease, the diseased planting rate of wheat and weeds, combined with the corn planting model, timely and accurate prediction and forecast of the occurrence trend of maize rough dwarf disease was conducted. Prevention.
2 Select the appropriate species: According to local conditions, select relatively resistant varieties, at the same time pay attention to a reasonable layout, to avoid the large-scale cultivation of a single resistance source varieties. In the 1970s, Yunong 704 had a certain resistance to the disease, 50, Ludan 053, Nongda 108, etc., which can replace Shendan 7, Dandan 53, and Dandan 22 and other susceptible varieties in production. In areas where disease-causing varieties have been planted for many years and are seriously endangered, it is particularly important to plant these varieties of resistant (resistant) disease. In Qufu City, the maize hybrids Ludan 50 and Lu Yuandan 14 have good resistance to rough dwarf diseases.
3 Adjust the sowing date of corn: According to the law of occurrence of corn rough dwarf disease, in the disease recurrence area, the sowing date should be adjusted so that the corn will avoid the occurrence period of the adult Spodoptera reticulata during the most sensitive period of the disease and reduce the incidence rate. Spring sowing maize should be appropriately sowed early, generally in late April in early May, wheat interplanting corn appropriately delayed, generally in the first five days of wheat harvest, try to shorten the commensal period of wheat and corn, so that appropriate late sowing. The corn planting models in Qufu mainly include wheat, corn grabbing and late sowing. Among them, the worst incidence of wheat is wheat, followed by grab corn and once again sowing corn. Spring sowing of corn should be planted before mid-April; summer sowing of corn should be appropriate in early June.
4 timely removal of weeds: roadside, field weeds is not only the provenance of weeds in the following year, but also the host of the winter wheat planthoppers. For weeds that remain in wheat fields, they can be sprayed after artificial weeding. The effect of weeding can reach 95%. The advantage of selecting soil treatment is that seedling corn does not coexist with weeds and reduces the activity space of SBPH, which is not conducive to the transmission of SBPH.
5 Strengthen field management: Combine Dingmiao, remove diseased plants in the field, concentrate deeply buried or burned, and reduce the sources of invasive disease. Rational fertilization and watering, strengthening of field management, promotion of corn growth, shortening the period of disease, reducing the chance of transmission, and enhancing the resistance of corn to disease resistance.
6 Virus source elimination: The maize rough dwarf virus is mainly wintered in wheat, grass weeds and sloughs. Therefore, wheat bush dwarf disease must be prevented and eliminated, and weeds in the fields, grounds, and ditches must be destroyed. To reduce the number of populations of Syrphidae, the specific method is to use 25% fluocinol at 50 g/mu after wheat returns to green. When spraying, the weeds around the wheat field must also be sprayed, which can significantly reduce the density of the insect population. If necessary, 20% of traceless water can be used or 45% of Roundup water can be used for 550 ml/mu, and the water is 30 kg. Spraying on the edge of the field to kill the weeds on the field and destroy the living environment of the plant.
2. Chemical control methods
1 Medicinal seed dressing: Corn seed coating and seed dressing with insecticides can effectively control the seedling stage of planthoppers and reduce the spread of rough shrinkage. When seeding, seed dressing with seed amount of 2% can effectively prevent the harm of Laodelphax striatellus, at the same time, it is beneficial for cultivating strong seedlings and improving corn disease resistance. After sowing, the pre-emergent soil treatment agent, such as 40% Bactohydraulic suspension, 50% Dua mixture, etc., is used to seal the soil with 30 kg of water per acre of 550-575 ml/mu.
2 Insecticide spraying: The crops with rough dwarf disease appear at the seedling stage of maize, and the diseased plants should be removed in time. According to the forecast of the insect status of the planthopper, 25% fluazifop 50 g/mu should be used in a timely manner. Sprayed once every 5 days, even sprayed 2 or 3 times, and sprayed with 40% virus A500 times or 5.5% plant disease spirit 800 times to prevent virus disease. For individual plots, the plots with poor soil treatment herbicides can be sprayed with 20% gram of herbicides at the corn line, 550 ml/mu, 30 kg water, and care must be taken not to spray corn plants. At the same time, Gramoxon has a rapid killing effect on weeds. Weeds can all die after 52 hours of spraying, which can reduce the space for the activity of the plant, and 45% of Roundup Water can be sprayed on the top of the field, but between corn rows. Try not to use, so as not to cause corn damage.
Corn rough dwarf disease is devastating, and it is difficult to cure once it has occurred. It is not realistic to spray some pesticide on the diseased plants so that it can return to normal. However, as long as agricultural control and chemical control are combined, the ring is tight. Buckle will certainly be able to control its spread.
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