In recent years, due to the abnormal climate, various pests and diseases in rice have increased year by year. Therefore, the majority of farmer friends must pay attention to the prevention and control of rice pests and diseases, in particular, they must pay attention to the prevention of this link, and often less investment in prevention can be achieved. To greater benefits. Here are the main pests and diseases that affect the current rice yield:
1. Sheath blight: Rice sheath blight is a kind of paddy field disease caused by the rice sheath blight pathogen. Generally, the damage is lightly reduced by 5-10% and severely reduced by 50-70%. With the increase of rice planting density and the increase of fertilization level, the disease has a tendency to increase.
Rhizoctonia begins at the stage of tillering in rice and mainly damages leaf sheaths and leaves. In severe cases, it can invade the stems and spread to the panicles. The occurrence of leaf sheath first appeared near the water surface with water-stained dark green dots, and gradually expanded into oval or mottled lesions. Leaf lesions are similar to leaf sheath lesions. Severe early onset of leaf disease, can lead to the rice plant can not be normal heading, even if the heading, lesions spread to the panicle, resulting in increased valley, grain weight decreased, and can cause lodging or the whole plant withered. High temperature and high humidity are most conducive to the occurrence, development and harm of rice sheath blight.
There are three main conditions that cause rice sheath blight:
(1) excessive dense planting: excessive or too late topdressing nitrogen fertilizer, rice is long and green; excessive irrigation, poor drainage, resulting in poor ventilation and light, high humidity in the field, are conducive to disease.
(2) In the high-temperature and high-humidity environment, the incidence is most prosperous. When the field microclimate reaches 25 --- 32 degrees, it encounters continuous rain, and the disease develops particularly quickly.
(3) Dwarf and multi-spike varieties have more tillers and dense leaves and are susceptible to disease.
What are the control measures for sheath blight?
The control period of sheath blight was from the end of the tillering period to the heading period, and the best was from the booting to the heading stage. In general, from mid-July to late July, the city will be in a proper period of prevention and control of rice sheath blight. During this period, field investigations should be strengthened and prevention and treatment should be carried out according to the incidence. In general, the incidence of end-stage tiller of the tillers reaches 5—10%, and the booting period reaches 10—15%. High-temperature, high-humidity weather for continuous control of 2 --- 3 times, interval 7 --- 10 days. Specific prevention methods are as follows:
(1) Salvage sclerotia to reduce the source of bacteria. After the depression, large areas of sclerotia floating on the surface of the water should be salvaged and taken out of the field to be buried or burned. The diseased straw cannot return to the field and remove the weeds in the fields.
(2) Strengthen cultivation management. Applying basal fertilizer, applying topdressing as early as possible, applying no nitrogenous fertilizer, increasing phosphorus and potash fertilizers, and using formula fertilization techniques, the rice will not be overleafed in the early stage, and will not grow in the medium term, and will not be greedy in the late stage. Irrigation should grasp the principle of shallow, mid-sun, and post-wetting to achieve shallow water for delivery, sufficient seedlings to expose fields, dry roots to promote roots, fat fields to re-sunshine, thin field light to the sun, long ears of moist, not early water, prevent premature aging.
(3) Drug control. This is the most effective way to control sheath blight. It should be treated early in the early stage of the disease. The main agents are: 5% Jinggangmycin, 25% Triadimefon and so on.
2. Rice blast
Rice blast is a rice disease caused by infestation of rice in different parts of rice by rice blast fungus.
Because the time and place of invading bacteria are different, the symptoms are different. Therefore, there are differences such as seedlings, leafhoppers, knots, panicles, branches and grains.
(1) Miao Miao: Mostly caused by seed bacteria, occurring before the three-leaf stage, generally do not form obvious lesions. The city rarely happens.
(2) Leaf aphids: Seedlings and adult plants can all occur on the leaves. The initial appearance of needle-sized brown spots quickly expands. It usually occurs during the peak period of childbirth. When it is severe, the far-infarction field is like a fire. There are four types of lesions:
Acute type: irregular spots, from the size of the needle to approximately the size of mung bean, large lesions slightly more pointed, water stains, dark green, back of dense gray green mold layer. The appearance of acute lesions is a sign of the prevalence of rice blast.
Chronic type: Acute type lesions can be converted to chronic type when the climate is dry. Spindle-shaped lesions, the outer part of the yellow poisoning department, the internal brown is the necrotic area, the center of the gray is the collapse of the Department, the brown necrotic thread runs through the lesion to the two ends, which is an important feature of rice blast.
Brown spots: lesions are brown dots, partially between veins. When the climate is dry, it mostly appears on the lower leaves of rice plants with strong disease resistance. At moderate and high temperatures, some become chronic lesions.
White point type: This type of lesion is rare, mostly appearing in the near-circular white spots on the susceptible leaves. When the weather is suitable for disease, it can be transformed into acute type lesions.
(3) Frugality: Generally occurs in the first and second sections under the flag leaf, and the first-born dark-brown small spots on the section gradually expand into a ring, finally turning the whole section into black, causing the stem section to bend or break.
(4) Panicles and neck ridges: Occurring on the panicle neck, rachis or branchlets, and having the greatest impact on yield. In the early stage, there was a small light brown spot with chlorosis on the edges. Afterwards, the disease department goes downwards and expands upwards. The length can be up to 2---3 cm, and the color is deepened. Finally, it turns black and dies or breaks, causing the valley or even the white spike.
(5) Grain pods: The early onset lesions are elliptical and gray in the middle, after which the entire grain turns into a dark grey pod. Late onset usually forms irregular dark brown spots.
The occurrence of rice blast disease is the result of a combination of factors. The main cause of the severity of the disease during the year is the climatic conditions; the main conditions that cause varying degrees of disease among the plots are the cultivation and management measures and the disease resistance of the varieties. In general, reasonable fertilizer and water management can increase the disease resistance of rice, even in the years of major occurrence, will reduce the incidence.
From the climate point of view, the most suitable temperature for the invasion of rice blast fungus is 24-28 degrees, and relative humidity is above 92%. If these two conditions exist at the same time, it is conducive to the onset; if the two are missing, the onset is slow or not.
From the perspective of cultivation and management, improper fertilization and excessive nitrogen fertilizer application, especially if used too late, often induce severe panicle blast.
From the aspects of disease resistance of the varieties, the resistance of rice to rice blast varies from variety to variety; even the same variety, at different stages of development, has different resistance to rice blast. Generally in the four-leaf period, tillering period, the end of booting to the ear when the most vulnerable to disease.
How to prevent and cure rice blast disease?
(1) Selection of resistant varieties: Different varieties of rice have different resistance to rice blast. The varieties that are resistant to rice blast are used in production as far as possible. For example, in the case of severe low temperature in 2006, Super Rice No. 1 showed its superiority against rice blast.
(2) Strengthen cultivation and management: Sowing appropriate amounts and cultivate stout old health-free or disease-free seedlings is the key to control seedling leafhoppers. Honda's base fertilizer should be sufficient in the early stage, pay attention to the combination of nitrogen, phosphorus, and potassium to promote rice plant growth balance. Before expiry of the tillering period, exposing the field in time can enhance the plant's resistance to diseases, control the occurrence and development of leafhoppers, and thus reduce the area of ​​chemical control. Heading water during the heading stage meets the needs of the flowering stage and wet irrigation during the grain filling stage, which is beneficial to the late maturity of the green culms and reduces the incidence. Disease areas and areas susceptible to disease should not be applied or prudent panicle fat, so as not to increase the incidence, resulting in reduced production.
(3) Chemical control: The rice in our city is usually headed on August 1st to 10th. Therefore, it is best to control the panicle and neckworm at about the end of July. The panicle pods have a great influence on the yield and quality of rice. If the weather forecast has a low temperature and rainy weather during the break period, it must be treated immediately. If the weather is conducive to the continued disease, spray it again during the grain filling period. The commonly used pharmaceuticals include: 40% Fuji No. 1 (rice indole), 2% kasugamycin, tricyclazole, and the like.
3, bacterial brown spot of rice
Bacterial brown spot of rice mainly damages rice leaves. In the beginning, it was a brown water-soaked spot, which later expanded into a spindle-shaped or irregular-shaped auburn stripe with a yellow halo on the edge. The lesion was gray-brown in the center, and lesions often fused into large strips, causing localized necrosis of the leaves. It usually occurs on both sides of the leaf tip or leaf edge.
Bacterial brown spot of rice is mainly caused by low temperature. The low temperature leads to a decline in rice resistance, which infects bacterial brown spots. Like a rare low temperature in late July 2006, many rice varieties have been infected with bacterial brown spot to varying degrees, and the entire paddy field is seen as "red".
The control of brown spot can be controlled by spraying some fungicides at the early stage of disease. Once sunny, the condition will no longer develop.
4, rice smut
Rice smut is a disease that damages the ear of rice. On a panicle usually one to several grains, severe up to a dozen or dozens of sickness. Rice smut disease not only destroys rice grain, but also consumes the nutrition of the entire diseased ear, causing other grains to become less full. As the number of diseased grains increases, the rate of empty maggots rises significantly, and the 1000-grain weight significantly decreases, resulting in a serious decline in the quality of rice. Toxins produced by rice smut are contaminated with rice, and human and animal consumption can cause poisoning and seriously endanger human and livestock health.
Different varieties have significant differences in disease resistance to rice smut. For example, in recent years, tight-spike varieties such as Pinshao No. 3 have relatively poor resistance to rice smut, and have a high incidence in fields.
One of the prevention and treatment of false smut disease is to use tetrafencarb for seed dressing before sowing; second is to remove the diseased plant early in time; third is chemical control, which can be sprayed with Triadimefon for 7-10 days before heading.
Pay attention to the use of triadimefon seed dressing, sometimes delayed emergence of 1 --- 2 days, but does not affect the emergence rate, late growth and yield.
5. Rice stem borer
The stem borer is a common pest of rice. In general, the output is reduced by 5---10%, and the serious reduction in output is more than 50%. In recent years, the damage of Slugs has been increasing year by year, especially in 2006, the occurrence of rice stem borer is generally heavier.
The borer borer larvae of the rice borer borer, due to the difference in the location of the damage and the growth period of the rice, showed damage in the spikes and panicles, resulting in spikes; infestation of rice stems after the second instar, dry heart during the tillering period, and dryness during the booting period Booting, heading stage causes white panicles, and the culm is caused by the mature period of filling. The different larvae hatched in the same egg larvae or the same strains of larvae infested in the field caused defoliation and white panicle clusters. The larvae often suffer from cluster damage. The boreholes are round and round. There are often a few insects outside the holes. There are often many larvae in a rice stalk, and many of them reach tens or even hundreds of heads. The stalk contains more feces.
Generally speaking, the early spring temperature rise is conducive to the occurrence of II. The spring rain and high summer temperatures are conducive to the occurrence of II.
Rice stem borer control measures
Prevention and treatment of stem borer can be taken by eliminating the source of overwintering insects, spraying pesticides and other methods. The insect source of S. indica is mainly in rice straw or rice straw, and the rice straw is removed or the rice straw is removed in time before transplanting to reduce the population of insects. Drug prevention and treatment of Sicia pupae is generally 5-7 days after the tillering stage of rice or the peak of panicle initiation and heading. When the dry sheath rate of 5 --- 8%, medication control. Generally, it is controlled by adding 18% of insecticidal water-repellent agent 250-300 ml per acre with water spraying, and the harm is serious. After 5-7 days, it is sprayed once more. When spraying, keep 3 - 5 cm of water in the field and keep the water layer for 3 - 5 days to ensure the efficacy.
For land that has been used for many years, it is best to replace the pesticide to improve the efficacy and achieve the desired control effect.
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