Occurrence and Control measures of Maize rough Dwarf Disease

Maize rough dwarf disease is a virus disease caused by maize rough dwarf virus, which can greatly reduce yield or even lose harvest when it is serious. It is a destructive disease. It is mainly harmful to a variety of gramineous crops and weeds, of which maize is the most susceptible and has the greatest impact on the growth, development and yield of maize.

1. At the beginning of the onset of the symptoms, transparent dotted spots appeared on both sides of the midrib at the base of the heart leaf, and then gradually extended to the whole leaf. The typical symptom is that there are waxy white strips of different thickness on the back of the leaf, the leaf sheath and the vein of the bract of the diseased plant, and there is an obvious rough and uneven feeling with the touch of the hand. The leaf is wide and short, thick and stiff, the leaf color is dark green, short, hard and brittle and upwelling, and the top leaves are clustered. The Internode was obviously shortened and swollen, the diseased plant was dwarfed, the height of the diseased plant was often less than half of that of the healthy plant, the male ear of the seriously diseased plant did not pull out or had no pollen, the female ear was deformed or the grain decreased, and the root system of the diseased plant was few and short. In addition, the young leaves of some diseased plants were curled in a bow or oxtail shape, the heart leaves were notched, and the trumpet mouth turned red to one side or the leaf edge turned red to the whole leaf.

2. Occurrence characteristics of maize rough dwarf disease was transmitted by gray planthopper in a persistent virus-carrying way. The disease resistance of maize was weak at seedling stage, and it was the most susceptible to disease at 2 leaves and 1 heart, and the sensitive growth period was before 7 leaves. The disease resistance is enhanced after jointing. In the fields where wheat rosette dwarf disease and green dwarf disease are serious, the incidence of maize rough dwarf disease in the following crop is often more serious. The practice shows that in the northern corn area, the disease of spring corn sown after the middle of April is more serious, and the later the sowing time is, the more susceptible the disease is. Summer corn is seriously affected by wheat interplanting, and the disease is light in direct seeding, and the disease is heavy in early sowing and light in late sowing.

3. The primary infection source of maize rough dwarf disease is mainly green dwarf plant in wheat field and gray planthopper overwintering with virus, which spreads in a persistent way. The host range of the virus and its vector gray planthopper is very wide, mainly Monocotyledon gramineae, such as wheat, rice, corn, sorghum, millet, barley and other crops, as well as weeds such as Niangmai, dogtail grass, horse grass, barnyard grass, thrush and so on. Corn is not a favorite host of gray planthopper, only when there is no suitable host in the field, gray planthopper takes corn as a transitional host and propagates parasitically. The gray planthopper occurs about 5 generations a year in the northern region, and the 2nd, 3rd and 4th generations of gray planthopper spend the summer on cereal crops and field weeds. After the emergence of autumn wheat, the fourth generation adults were transferred to the wheat field, and the maize rough dwarf virus was also transmitted to wheat, and overwintered in the wheat seedlings and the fifth generation (overwintering generation) gray planthopper, forming an annual infection cycle.

In the corn producing areas of northern China, the wheat area is large, and most of them are wheat-maize continuous cropping mode, coupled with the existence of a large number of Gramineae weeds, which provide a rich source of toxin and a good parasitic environment for the occurrence of maize rough dwarf disease. At the same time, summer corn is mainly planted in northern China, with wheat ridge interplanting and no-tillage and on-demand sowing after wheat. The susceptible stage of maize seedling often meets and overlaps with the migration peak of the first generation of gray planthopper, which provides a favorable opportunity for the infection of the disease. If the winter is warm and the spring is dry, Rain Water is suitable for the overwintering and reproduction of gray planthopper, and the first generation of gray planthopper occurs greatly, which leads to the outbreak of maize rough dwarf disease.

Fourth, the prevention and control strategy of maize rough dwarf disease should emphasize the principle of prevention and early prevention, and agricultural control should be emphasized, supplemented by chemical control measures in the critical period. The occurrence of maize rough dwarf disease is completely caused by the transmission of poisonous gray planthopper, so eliminating or avoiding the transmission and infection of gray planthopper is an important way to prevent the occurrence of rough dwarf disease.

(1) Agricultural control measures

1. Clear weeds in the field. Kill stubble in time after autumn harvest and remove weeds in the field to reduce the overwintering and summer hosts of gray planthopper and virus, so as to reduce the harm of maize rough dwarf disease.

2. Control gray planthopper in wheat field and reduce virus transmission vector. Herbicide was used to control weeds in wheat field before winter, early spring wheat jointing stage combined with red spider spraying to control overwintering adults; after wheat heading, combined with disease control and pest control, three control was carried out, and the first generation of gray planthopper was also controlled.

3. Adjust the sowing date of corn. Avoid the migration peak of gray planthopper and facilitate chemical control, avoid the peak of adults in overwintering generation.

4. Combine the seedlings to fix the seedlings, pull out the diseased plants in the field in time, and reduce the chance of virus transmission. Strengthen field management, reasonable fertilization and watering, enhance the resistance and tolerance of maize plants, and reduce the occurrence of diseases.

(2) Pesticide control measures

1. Seed dressing with chemicals. At the same time, continuous planting is advocated so that the sowing date is basically the same.

2. Spraying insecticides to control gray planthopper in corn field and nearby weeds before and after sowing and seedling stage.

3. When the disease occurs at the seedling stage, the diseased plants should be pulled out in time, the seedling setting time should be postponed appropriately, and antiviral agents should be sprayed to inhibit the proliferation of the virus and accelerate the synthesis of chlorophyll, so as to reduce the occurrence and harm of the disease and increase the yield.