There are 13 kinds of rice pests, such as large borer, dihua borer, three chemical borer, Taiwan rice borer, rice longitudinal leaf borer, straight-striped rice butterfly, rice borer, rice planthopper, leafhopper, rice thrips, etc., but the pests that directly cause rice yield reduction are mainly rice drill heartworms (the general name of rice drill borer type pests), which are large borer, dihua borer and three chemical borer. From an entomological point of view, the great borer belongs to the nocturnal moth family, and the dichotic borer and the tricolor borer belong to the moth family; In terms of the size of its adult insects, the size of the big borer is "thicker" than that of the dihua borer and the tri-chemical borer, while the body size of the dihua borer and the tricolor borer is relatively "slender". Now let's briefly introduce the harmful symptoms, living habits, occurrence rules and prevention methods of the two and three borers.
Dihua borer is a genus of Lepidoptera, a fully metamorphosed insect, which undergoes 4 developmental morphologies of egg-larvae-pupae-adult insects throughout their lives.
1.1 Harmful characteristics
Rice can be affected by dicarbonate borer from the seedling stage to the mature stage. In the early stage of pest, the hatching larvae cluster on the inner side of the leaf sheath to eat, the leaf sheath appears water-stained macula, the later leaf sheath withers yellow, the leaves gradually die, manifested as a dry sheath; after 2 years of age, the larvae begin to moth into the rice stem to feed as a pest, the tip of the sword leaf of the moth stem becomes yellow, the severe heart leaf withers and dies (dry heart seedlings), there are circular borer holes on the affected stem, and there are often a large amount of insect feces outside the hole; After the larvae drill the moth rice plant, they behave differently depending on the site of the victim and the growth period of the rice: the tillering stage causes a dead sheath and a dry heart; The gestational panicle stage causes withered gestational and white spikes; During the maturity stage of grouting, the plant is injured, the grains are increased, and it is easy to collapse in case of strong winds; The incubating of different larvae or the same larvae in the same egg block often causes dry heart clusters and white panicles in the field. Larvae are often clustered, and there are often multiple larvae in a rice stalk, up to 10 heads, and there is more insect feces in the stalk.
1.2 Habits of life
Adults lurk at the base of rice bushes and weeds during the day, are nocturnal, and are phototropic. Eggs can be spawned on the evening or 2nd day after feathering. Female moths prefer to lay eggs on tall rice plants with thick green leaves, wide leaves, and thick stems. Eggs are mostly laid at a leaf surface 3 to 7 cm from the tip of the leaf, but can also be laid on the leaf sheath. More spawning occurs at the tillering stage and the gestational panicle stage of rice;
Spawning is less during the rejuvenation, jointing and ear filling phases. After hatching, the ant borer (hatching larvae) generally crawls down the rice leaf or spits silk down, enters from the heart leaf, leaf sheath gap or leaf sheath outside the leaf sheath, and first gathers in the leaf sheath to feed on the inner wall tissue, and after 2 years of age, the larvae begin to moth into the rice stem to feed as a pest. The larvae have the habit of changing plants to become pests, and when there is insufficient food or rice growth is blocked, they frequently change plants and aggravate the damage. After the larva matures, it mostly pupates in thin cocoons within the stem of the affected crop (inside some dead leaves). Dimorph is an oligotrophic pest, and the host plants include rice and russet.
1.3 Occurrence
Dihua borer occurs in 2 to 3 generations in 1 year in our county, with 4 to 6 instar larvae overwintering in rice piles, straw, russet white and weed stalks around the rice field and on the field, but due to the complex overwintering environment of the erhua borer, the pupae and feathering time of the overwintering larvae are not neat. Therefore, the feathering time often lasts for about 2 months, forming multiple moth peaks, resulting in generational overlap, which makes it difficult to predict and control work.
Tricoloma borer is a lepidoptera, a fully metamorphosed insect that undergoes 4 developmental morphologies of egg-larvae-pupae-adults throughout their lives.
2.1 Harmful characteristics
The pest symptoms of the three borers are basically the same as those of the dimorph borer and the big borer, and the larval borers can also cause dry heart seedlings, dry pregnant ears, white spikes, insect injury plants and the corresponding dry heart groups and white panicle groups, but will not cause dry sheaths. The larvae of the three borers have 2 pest characteristics that are different from other borers: First, the larvae only feed on the inner wall of the stem, the white and tender tissue of the leaf sheath, the pollen and stigma in the ear buds, and basically do not eat the part containing chlorophyll; Second, the larvae like to be single-headed pests, generally each larvae alone 1 plant of rice tillers, after mothing in, first in the leaf sheath and stem nodes of the appropriate part to do "ring cutting", most of the vascular bundle bite off, incision neatly, called "broken ring". Larval pests occur at the seedling stage and tillering stage, causing rice heart leaf damage, water loss longitudinal roll, slightly faded green or bluish white, shaped like an onion tube, called false dry heart. The curly heart leaves are withdrawn, and the section is neatly seen, and the false dry heart turns yellow and dies to become a dry heart seedling, but the other leaves are still blue-green. Mothing in the late stage of the pregnant ear and the beginning of the panicle extraction, biting off the neck of the panicle, resulting in a white panicle. This kind of white spike is easy to pull up, but the sword leaf sheath is not yellow, peel off the dead sheath, there are ring-like neat break marks on the spike stem, peel off the spike stem, there are insect chips in the stem, less insect dung, green and white dry. The damaged rice plant has small borer holes, no insect feces at the holes, and white fine-grained insect droppings in the stem, which are easy to distinguish from the dry heart seedlings caused by the damage of large borers and dimorph borers.
2.2 Habits of life
Adults lurk at the base of rice bushes during the day, are nocturnal, and have strong phototropism. Adults mostly feather in the evening, and feathered female moths can lay eggs on the same day. Egg masses are mostly produced on the surface of leaves or leaf sheaths, and adult insects have a similar selection habit to spawning sites as dimorphs. After the larvae hatch, most of them climb to the tip of the leaf, and the sagging silk drifts with the wind to disperse the moths on the nearby rice plants. The larvae hatched from the same egg block are infested with nearby rice plants, forming "dry heart clusters" or "white panicle clusters" in the field. Larvae have the habit of turning plants into pests, they can be transferred 1 to 3 times in a lifetime, it is more common to transfer plants with 3 to 4-year-old larvae, and the transfer method varies according to the age of the insects, and the 2- to 3-year-old larvae mostly move outside the plant with "nakedness"; The 3rd to 4th instar larvae are mostly carrying leaf sacs or stem sacs, in which the larvae hide, or crawl or float on the surface of the water with their heads outstretched, find new plants, fix the leaf sacs on the leaf sheath, and then moth into the rice stem. Most of the rice plants that were killed were 1 plant and 1 larvae. After the larvae mature, they move down to the base of the rice stem for pupae. The borer is a monogamous pest that only harms rice and wild rice.
2.3 Occurrence
The borer occurs in 2 to 3 generations in 1 year, with old mature larvae overwintering in rice piles. Overwintering larvae pupate and feather when the temperature rises above 16 °C in the following spring.
3 Prevention and control methods
The occurrence and harm characteristics of the two borers and the three borers are basically the same, so the prevention and control methods are also similar, mainly based on agricultural prevention and control, and the prevention and control strategy of combining prevention, avoidance and treatment is adopted. On the basis of grasping the occurrence period, amount and degree of occurrence of pests, rational application of chemical pesticides, and rice varieties with strong insect and disease resistance can also be selected if conditions permit.
3.1 Agricultural control
3.1.1 Eradication of the source of overwintering insects
Machine-cut rice stubble is ploughed and planted before winter or shallow rotary tillage is burned to burn rice stubble, and the broken stalks are returned to the field. Before spring, the field straw is cleaned up, the field edge and ditch edge are uprooted and the weeds are destroyed in a concentrated manner, and the unstructed straw is sealed with a medicated agent to reduce the source of insects, destroy the wintering sites of borers, and reduce the survival rate of borers overwintering.
3.1.2 Update rice varieties
Reduce and phase out the varieties of susceptible pests and susceptible rice blast planted all year round, and adopt varieties with strong disease and insect resistance to reduce chemical control pressure.
3.1.3 Fertility bed dry breeding
Compared with water seedlings, the amount of eggs dropped by the fertile bed drought seedling borer is low, and the field is less affected.
3.1.4 Flooding to extinguish pupae
Hatching larvae of the dimorphate borer endanger the leaf sheath of rice, so the late-maturing winter cropping field and the grass seed seeding field are flooded at the pupal stage 3. 5 ～6． 5 cm deep, which can drown most pupae; Or in the first and second generation of larvae in the old maturity stage to dry the field water, let the larvae drill into the roots to pupate, the pupal stage flooded in deep water for 3d, most of the pupae can be drowned, the insecticidal effect can reach more than 90%.
3.1.5 Late sowing at the right time, cultivation to avoid borers
The comprehensive promotion of rice light cultivation technology can appropriately postpone the sowing period of rice, so that the seedling stage of rice that is prone to egg fall avoids the peak period of egg laying of a generation of borers, reduces the amount of eggs fallen in the rice field, reduces the incidence and occurrence base of a generation of borers, and achieves the purpose of cultivating borer avoidance.
3.2 Chemical control
3.2.1 Principles of pharmaceutical prevention and control
(1) Adhere to the prevention and control strategy of "ruthlessly curing the first generation and popularizing the second generation". A generation aims to lower the base number, and the prevention and control of rice fields is concentrated, and the prevention effect is obvious; The second generation aims to control the harm and ensure a bumper harvest. (2) Grasp the insect situation and ensure that the drug is applied at the peak of egg hatching. (3) Select the right agent to ensure the effectiveness. Pharmaceutical prevention and control should be based on different regions, different generations of local conditions to select agents, minimize the number of drugs and dosage, so as to rotate drugs, slow down drug resistance, choose low toxicity and biological pesticides. (4) Correct application of the drug, exert the effect of the drug.
3.2.2 Borer hatching rules
According to the local agricultural department's insect situation monitoring and reporting, master the pesticide application period, in the second 2 to 3 days before the peak hatching of the two borer eggs (after years of prediction, the first peak period of rice borer in our county is generally between July 17 and 20), and then every 7 days to enter the peak period of incubation, and 3 generations occur continuously. Or when the sheath is first seen, it is in the early larval stage (1 to 2 years old) for control.
3.2.3 Specific prevention and control methods
According to the peak period of borer hatching, effective control measures are formulated, combined with the drug of rice blast, before the first incubation peak of borer hatching, a one-time control of borers is carried out at 667m2 with 75% tricycloxole 40g + 30% Avi insecticidal single 40g (or DuPont Kangkuan 5ml) of water; Interval 5 to 7 days (i.e., before the second peak) the second dose of the second dose, the second dose according to 667m2 with 40% rice blast 80ml + 25% avitrizole phosphorus 100ml + propiconazole 300g / l water 30kg, the ear neck plague, borers, rice aspergillosis for integrated control; Before the peak of the 3rd occurrence: 367 m2 with 20% tricyclicazole 100 g or (2% priscin 80 ml) +30% aviracidic single 40 g + propylene ring 300 g / l +70% imidacloprid 20 g + potassium dihydrogen phosphate 100 g 30 kg of water for integrated control of borers, panicle neck blast, planthopper oryzae, aspergillosis.
3.2.4 Control techniques of rice dimorphs
Correctly select pesticides, pay attention to the rational compounding of agents, spray the rice base, and maintain a water layer of 3 to 5cm in the field after the drug. Water consumption should be sufficient: not less than 30kg /667m2. Morning and evening administration: before 9 a.m., after 5 p.m. Pay attention to the weather forecast, the drug needs to be re-administered in case of rain within 4h of the drug. Pay attention to the timely use of drugs before the pest drills the heart.
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