In recent years, many farmers have been distressed. What about rice dwarf? Will this happen? In fact, rice dwarf disease is a serious disease that threatens the growth of rice. The occurrence of this disease directly leads to a decline in the quality and yield of rice. It also poses a huge threat to China's food security. This article introduces in detail the hazard symptoms, occurrence rules and prevention methods of rice dwarf disease, for farmers to refer to.
1. Pathogens and characteristics of rice dwarf disease
When rice dwarf virus invades rice, it can cause dwarf rice. The virus is a spherical polyhedron with a body length of 75 nm and a double-stranded ribonucleic acid structure. The passivation temperature is between 40 and 45 ° C, 1000 to 100,000 times is the dilution boundary of the virus, and the in vitro survival period is 48 hours. The leaf cells are white and have a hollow X-like body similar to a sphere.
2. Rice dwarf disease infection cycle
After harvesting the late rice, the virus will parasitize the larvae of the leafhoppers for winter. Until April of the following year, when the farmland is ploughed, the leafhoppers will fly to the seedlings of the early rice, and the virus will find an opportunity to spread. After the harvest of pure single-season rice, Ye Hao will continue to hide in the farmland, weeds, ditch, grass and other grasses to continue to survive, and carry out reproduction work until the next year of cultivation, Ye Hao continues a new round The rice dwarf virus spreads work. After two seasons of rice planting, the spider mites will fly to the seedlings of the late rice or the Honda to spread the virus after harvesting the early rice. After harvesting the late rice, the spider mites will spread the virus like pure single-season rice.
3. The occurrence of rice dwarf disease
The occurrence of rice dwarf disease is disturbed by the following factors.
Climatic factor
Spring and winter leafhoppers hide in farmland, weeds and ditch. The temperature changes in these places are mild, rainfall is less, food is sufficient, the survival rate of leafhoppers overwintering is higher, and the number of leafhoppers carrying viruses is high. Rising, spring ploughing can cause a wider spread of the virus. In the summer of June to August, when the temperature is relatively high and dry, it is also conducive to the growth of leaf axils, resulting in the occurrence of dwarf disease in late rice or pure single season.
2. Selection of rice varieties
Ye Wei likes the varieties with deeper leaves, larger leaves and stronger tillering ability. Rice with different varieties has different resistance to dwarf disease. The resistance of high rod is stronger than that of short rod, and the resistance of hybrid rice is stronger than that of indica rice. In the same variety of cultivation, the infection rate of late rice is higher than that of early rice, and it is divided into seedling stage and tillering stage for infection.
3. Planting factors
Farming with single or double seasons or serious flower arrangement, or winter farmland, green fertilizer field or farmland with more weed growth in April will bring great convenience to the growth and reproduction of leafhopper. The planting of farmland is a method of interplanting early, middle and late rice to facilitate the growth and reproduction of black-tailed spider mites. After the harvest of early rice, the Honda and Putian of the mid-season provide temporary habitat for leaf blast, until the planting of late rice. The infection of the virus can be spread in the seedling stage and in the tillering stage.
4, rice dwarf disease symptoms
After dwarf disease in rice infection, rice is half as small as normal plants, with obvious tillering, short and stiff leaves, twisted leaf tips, deeper leaves than normal rice, and newly emerged leaves or sheaths can be seen and veins Parallel yellow-white dotted dots. After suffering from dwarf disease, the roots of rice are dysfunctional, and the supply of nutrients is abnormal, resulting in the gradual yellowing of rice. The growth height of rice after dwarf disease in the seedling stage and tillering stage was 1/3 to 1/2 of that of normal rice plants. The leaves could not be stretched and the harvesting could not proceed normally. Other viral infections in rice occur from jointing to booting, resulting in one or more branches at high nodes and fewer rice grains on the branches. If the rice is infected at the booting stage, the flag leaves will be shortened, resulting in the appearance of a half-necked ear or an all-inclusive ear. The ear of the rice becomes smaller and the growing particles are empty. These factors will affect the harvest of rice.
Among the pathogenic types of rice virus disease, there are black streaked dwarf disease, yellow dwarf disease, common dwarf disease, verticillium wilt, and stripe leaf blight. All are caused by the corresponding virus. In addition to Verticillium wilt, the occurrence of Verticillium wilt is caused by the invasion of rice by the bacteroids. Viruses that interfere with rice have other hosts in addition to parasitic on rice.
5. Rice dwarf disease prevention and treatment method
The occurrence of rice dwarf disease is disturbed by the following factors.
1. Comprehensive prevention and control measures
The comprehensive prevention and control measures proposed in this paper are combined with drugs and agricultural control. The focus is on long-term spray protection of rice. The prevention measures and control effects are shown in Table 1.
2. Agricultural control
The content of prevention and control of agriculture: 1 Isolation of farmland with high incidence of disease during cultivation, centralized supervision of seedlings during seedling period, and reduction of virus infection. 2 When planting, the method of widening and narrowing is adopted. When filling the water, pay attention to the height of the water level, properly dry the field, prevent sealing and greed. Respect the actual growth of rice in the work of base fertilizer and top dressing, according to its needs, to avoid excessive growth of rice. 3 varieties of rice with the same variety were planted in contiguous, blocking the migration of black-tailed spider mites, and effectively carrying out pest control and disease prevention work. 4 If there is any infection, it should take immediate measures to prevent the spread of the virus. 5 The harvesting of rice should be carried out by means of concentrated harvesting of parts, starting from four weeks, so that the leaves can be concentrated in the middle and then applied to kill them. After the end of the harvest, the weeds on the edge of the field and the ditch should be cleaned up to control the infection of the virus. 6 Rice should use varieties with strong disease resistance, and carry out rotation to eliminate the emergence of resistance.
3. Biological control methods and physical control methods
The cultivation of rice can promote the method of rice and duck co-culture or the vibration-frequency trap light to control the spread of the virus. In addition, natural enemies and artificial nets can be used to kill and kill the spider mites, effectively preventing the occurrence of dwarf disease.
4. Chemical control measures
Chemical control measures are carried out against insects carrying pathogens. Control can be carried out in three stages, one stage, 4 to 5 period, when the tillage of early rice is transferred to the seedling or Honda period. In the second stage, the first generation of spider mites in the first half of June was assembled from a single-season ploughing site to a single-season seedling or Honda period. In the third stage, the second and third generations of the leafhoppers in the middle and late July migrated to the time of the paddy field planted in the late rice after the harvest of the early rice.
Commonly used chemical agents are: 50% of chlorpyrifos EC, 50% of Isoprocarb, 25% of insecticidal double agent, 90% of crystalline trichlorfon, content is 50% of the chlorpyrifos should be sprayed according to the actual situation of the rice field virus infection.
4.1 The efficacy of 50% Isoprocarb. Isoprocarb is a chemical insecticide of carbamic acid, which has the effects of contact, stomach poisoning and fumigation. As a nerve poison, it can cause the nerves of insects to paralyze and die. The effect on the pests of spider mites is more significant, but the effective period is shorter, and there is no harm in the natural enemies of spiders or locusts, and humans and animals will show slight poisoning.
Spraying method, spray 20% of Isoprocarb emulsifiable oil 1000-1500 times and then spray it again, and then carry out once every 5-7 days. The spraying should last 2~3 times, and the interval of safety period should be 14 days. Corresponding precautions: The enemy can not be used for 10 days before and after spraying the drug, which can cause poisoning to bees and low toxicity to fish.
4.290% crystal trichlorfon. Organophosphorus insecticides have low toxicity, broad spectrum of insecticides, strong stomach toxicity to pests, and contact toxicity. They are permeable to plants but have no systemic conduction.
In the control period, spray with 90% crystal trichlorfon 800 ~ 1000 times. Spray evenly and thoughtfully, apply once every 5 to 7 days, 2 to 3 times in a row, and the safety interval is 7 days. Should pay attention to the use: 1 generally use concentration of about 0.1% for crops without phytotoxicity, sorghum, beans are particularly sensitive to the drug, easy to produce phytotoxicity, should not be used; 2 drug dilution should not be placed for too long, should be used now ; 3 can not be used with alkaline drugs or at the same time.
4.350% chlorpyrifos EC. Organophosphorus insecticides are highly effective, broad-spectrum, moderately toxic, and have a contact and stomach toxicity to pests. It can penetrate plant tissues to kill drill-bit pests and has a long residual period.
In the control period, spray with 50% thiophene emulsifiable concentrate 1000 times, spray should be uniform and thoughtful, to improve the control effect, apply once every 5 ~ 7d, 2 or 3 times in a row, the safety interval is 21d. Should pay attention to the use: 1 This product has phytotoxicity to sorghum, and it is easy to produce phytotoxicity to cruciferous vegetables such as radish and rapeseed. Pay special attention when using it; 2 It can be mixed with common acaricides and fungicides, but not with Alkaline pesticides should be mixed; should be used now; 3 This medicine is more toxic to fish, do not pollute rivers and fish ponds when used; 4 Store in cold and dry place, and pay attention to fire prevention.
4.450% mixed with emulsifiable concentrate. A carbamate insecticide, the main active ingredient is a mixture of vanizan and vancoside. It has a strong contact and stomach toxicity to pests. It is mainly used to control rice leafhoppers. It is used at the peak of nymphs and has a fast knockdown speed and good efficacy.
In the control period, spray with 50% mixed Weiwei EC 1000 times, apply once every 5 to 7 days, for 2 to 3 times, and the safety interval is 7 to 10 days. Should pay attention to the use: 1 can not be mixed with alkaline pesticides ; 2 can not be used on tobacco, so as not to cause phytotoxicity; 3 the drug has a fruit thinning effect, the best use 2 to 3 weeks after the flowering period.
4.525% insecticidal double water agent. The organic nitrogen phycocide insecticide has a broad spectrum of insecticides, high efficiency, strong stomach toxicity, contact and systemic action, and has certain fumigation and ovicidal effects. The poisoned pests generally die slowly, but they quickly lose their ability to feed and eventually die.
In the control period, spray with 25% insecticidal double-water agent 500 times solution, once every 5 to 7 days, for 2 to 3 times, the safety interval is 15 days. Should pay attention to the use: 1 The drug is highly toxic to the silkworm, and must be used with caution in the silkworm area; 2 in the prevention and control of rice-based pests, avoid dry field medicine; 3 beans, cotton and cabbage, cabbage and other cruciferous vegetables, It is more sensitive to the drug, especially in summer, it is easy to produce phytotoxicity; 4 Do not mix with strong alkaline substances.
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