What are the common diseases and insect pests of cotton? Control techniques of Diseases and insect pests in Cotton

Cotton is one of the most important crops in the world, with large output and low production cost, so that the price of cotton products is relatively low. The fiber can be made into a variety of fabrics, from light and transparent Bari yarn to thick canvas and velveteen. It is suitable for making all kinds of clothes, furniture cloth and industrial cloth. The countries with the highest output are China, the United States and India. Let's take a look at cotton pest control technology.

APHIS gossypii

[damage characteristics] the seedling aphid occurred after emergence to budding, and the control began when the leaf curling rate reached more than 30%. The cotton aphid was at its peak from mid-June to late July.

[control method] 10% imidacloprid wettable powder + 800-fold solution of new high-fat film or 15% EC + 800-fold solution of new high-fat film can be selected for uniform spraying of stems and leaves. When the aphid occurs in the bud and boll stage, due to the high temperature, we can choose 3% acetamiprid EC 2000 times liquid plus 40% chlorpyrifos 1200 times solution + new high fat film 1200 times solution to control aphids and other pests. After the cotton plant is closed, 80% dichlorvos EC + 800 times of new high fat film can be sprayed on cotton ridges in sunny and windless evening, which has a good effect on aphids and can also control cotton red spiders.

Cotton spider mite

[hazard characteristics] it began to appear in cotton fields in early May, when the temperature was lower, the reproduction rate was slow, the number of single-leaf mites was less, and the damage of cotton seedlings was less. From early June to late July, the temperature rose rapidly, cotton spider mites began to multiply in large numbers, concentrated damage, and the damage was rampant in dry years.

[control method] you can choose 15% trimethoprim EC + 800-fold solution of new high-fat membrane, or 1.8% adriamycin + 800-fold solution of new high-fat membrane for spray control.

Cotton bug bug

[damage characteristics] the damage of cotton bug to cotton is increasing year by year, and the chemical control period is in the middle and late June, during which the cotton plant is relatively young. In case of heavy rain and high relative humidity in cotton field, it is beneficial to the harm of cotton bug bug. This period is the key period of control.

[control method] in cotton bud stage and boll stage, 5% acetamiprid EC + 800-fold solution of new high-fat film or 4.5% cypermethrin EC + 800-fold solution of new high-fat film can be used to control cotton bollworm at the same time.

Cotton bollworm

[damage characteristics] Helicoverpa armigera is the main pest in cotton bud and boll stage, which generally occurs 4 generations a year. The cotton is mainly damaged by the second and third generations, and the larvae eat buds, flowers and bolls, and the eaten cotton bolls are easy to rot and fall off or become stiff petals.

[control method] physical control of ①: install Jiaduo frequency vibrating insecticidal lamp in cotton concentrated planting area, equipped with one set per 60 mu, the effect of continuous use is better. ② chemical control: you can choose 90% Wanling wettable powder + new high-fat film 800x liquid, 4.5% cypermethrin EC + new high-fat film 800x liquid or 1.8% avermectin + new high-fat film 800x solution for stem and leaf spray, spray once every 7 days for 3 times in a row, and evenly spray 20% cypermethrin EC + new high-fat film 800x solution or 20% cyanma EC 1500 times when cleaning up the residue in the later stage.

Fusarium wilt

[hazard characteristics] Fusarium wilt is a disease that harms the vascular tissue of cotton, causing discoloration, dryness, shedding and wilting of cotton leaves, and sometimes successively withered, affecting the yield.

[control method] in the cotton bud stage, Huanghuangweiling can be sprayed with 40 grams per mu of water (preferably with continuous irrigation) for 3 or 4 times.

Verticillium wilt

[hazard characteristics] generally, the disease began to appear at the stage of 3-5 true leaves, and a large number of diseases occurred in the field after budding in the middle and later stage of growth, which could easily lead to the death or wilting of the whole plant.

[prevention and control methods] the general medicaments include carbendazim, methyl topiramate, Kehuangku, withered yellow base factor, cotton Sanqing, etc., and add nutrition regulators such as potassium dihydrogen phosphate, boron fertilizer, boron plus selenium, zinc fertilizer, zinc plus selenium, Tianfengsu, fish protein, etc., every 5-7 days, spray 2 times for 3 times.

Spodoptera exigua

[hazard characteristics] Spodoptera exigua is an omnivorous pest, which occurs for 4 to 5 generations a year, with serious generation overlap and irregular age. High temperature and drought climate factors and mixed cultivation conditions of many kinds of crops are beneficial to the occurrence of beet armyworm. Cotton fields with extensive management and weeds are more serious.

[control method] 0.2% methylvitamin salt + 800-fold solution of new high-fat membrane or 25% diflubenzuron suspension + 800-fold solution of new high-fat film can be selected and sprayed evenly on cotton plants and field weeds for 2 times for 3 times.

Cotton pest control technical expert, Hello! Many buds and leaves of cotton in our village have been eaten by worms, which are eaten by worms. We can't see what insects should use during the day. Please reply as soon as possible! Thank you name: Yao many unit: contact telephone number: 2008-06-26 expert answer Comrade Yao many: Hello, according to the situation described, it is impossible to judge what insect pests caused. Because there are more than 300 species of cotton pests in China, more than 30 species are common, cotton aphids and cotton bollworms are in the northern precocious cotton areas, and cotton aphids, yellow tigers, blind Toona sinensis and cotton bollworm in the inland areas of northwest China. Cotton aphids, cotton bollworm, ground tiger, blind Toona sinensis, leaf mites, corn borer, small bridge worm and red bollworm in the Yellow River basin. The cotton areas in the Yangtze River basin are red bollworm, leaf mite, blind Toona sinensis, cotton aphid, cotton bollworm, ground tiger, cotton leafhopper and snail, while in South China, there are diamond diamond, red bollworm, cotton bollworm, cotton leafhopper and red Toona. The above is for reference only. Control techniques of Common Diseases and insect pests in planting Maize

Corn is often harmed by all kinds of diseases and insects in the process of production, and its yield is seriously reduced. For example, in the epidemic years of leaf spot disease, the yield can be reduced by 15Mu30% due to the disease, and by more than 50% in seriously diseased fields; the harm of corn borer usually reduces corn production by about 10%, and by about 30% in serious years. There are many kinds of diseases and insect pests that harm corn, including large leaf spot, small leaf spot, head smut, bacterial wilt, ear rot and virus disease. in local areas, there are serious damage to sheath blight, brown spot, rust, round spot, gray spot and so on; the main pests are corn borer, ground tiger, armyworm, red spider and so on.

Maize leaf spot and small leaf spot

[symptom identification] the typical symptom of corn leaf spot is that the small spot rapidly expands into a long prismatic spot, the serious one is more than 10 mi 30 cm long, and sometimes several spots are linked together to form irregular spots. The disease spot is immersed in water at first, and soon becomes green, and finally becomes black mildew, that is, the conidiophores and conidia of the pathogen.

[symptom characteristic] the symptom characteristic of corn leaf spot is that the disease spot is small, generally no more than 1 cm long, the width is only between two leaf veins, nearly oval, the color of the spot edge is dark, it is Auburn. In addition, the number of disease spots is generally more.

[pathogenic factors] the germination and invasion of spores and the formation and spread of spores all need certain climatic conditions, of which temperature and humidity are the main. The optimum temperature for spore formation, germination and invasion of Xanthomonas oryzae was 20 ℃ 25 ℃, while that of Xanthomonas oryzae was slightly higher than that of Xanthomonas oryzae, and the optimum temperature was 20 Mel 32 mol. Therefore, the small spot is more serious in the summer corn planting area, while the big spot is more serious in the spring corn area. Heavy rainfall and high humidity are easy to cause the epidemic of diseases.

[control methods] the prevalence of the disease is determined by three factors: first, planting susceptible varieties in a large area; second, the existence of a large number of bacteria; and third, suitable environmental conditions for the disease. Therefore, the prevention and control of diseases should start from these three aspects.

Selection of disease-resistant varieties for ①: this is the fundamental way to control large and small spot. There are obvious differences in disease resistance among different varieties. At present, the disease-resistant varieties commonly used in production are Baoyu 7, Tunyu 7, Yunrui 7, Haihe 14, Qing3, Huidan 4, Xinghuangdan 892, Denghai 3, Dianfeng 4, Yunrui 1, Yunrui 2, Yunrui 8, Ludan 10, Qichen 3, Haihe 2 and so on.

Deep ploughing of ② rotation can reduce the amount of bacteria, thoroughly remove the disease and residue in the field after corn harvest, and reduce the source of primary infection. In the early stage of the disease, the lower diseased leaves were knocked out before the disease occurred in the bottom 4 leaves, which could reduce the degree of the disease. It is suitable for early sowing and has the effect of avoiding disease. Strengthening the management of fertilizer and water can improve the disease resistance. The poor growth of the plant is easy to be infected, and the resistant varieties can not show their disease resistance potential even when they are short of water.

③ medicament control: 40% Ke Fei San emulsion 500ml 1000 times, 50% Tuichuite wettable powder 800x, 50% Daoxianjing 1000 times, 50% methyl topiramine 500,800 times. It is necessary to spray again every 7 days or so.

Maize head smut

It is mainly harmful to the ear and flowering of corn, and there is usually no harvest of the whole plant once the disease occurs. Therefore, the incidence of the disease is equal to the loss rate of the disease, and the harm is quite serious. Commonly known as "Wumi" or "gray bag".

[symptom identification] the symptoms of systemic diseases invaded from maize coleoptile at seedling stage were mainly after heading. The appearance of the diseased ear is shorter than that of the normal ear, the base is large and the tip is pointed, and there is no filament at the top. Sometimes one side of the bract split, revealing black powder, the diseased ear all turned into a dark brown pile of spores, the spores were not easily scattered, which were mixed with the remains of the vascular bundles of corn plants. The plants with smallpox disease generally have no spike, and the tip of the newly extracted flower axis becomes a small pile of black spores, and sometimes the floret deforms into leaves after smallpox extraction.

[pathogenic factors] chlamydospores fall into the soil, mixed with manure or carried by seeds to survive the winter. In the following year, under suitable conditions, chlamydospores germinated and invaded the host seedlings through the coleoptile. After the invasion, the hyphae entered the plant growth point, spread to the ear and smallpox, formed a pile of spores, and then released spores after maturation, completing the infection cycle once a year, and there was no further infection. When the soil temperature is low and dry, the emergence of maize seedlings is slow, which increases the chance of bacterial infection, and the incidence is high, which is conducive to the epidemic of head smut. Therefore, the occurrence of head smut is serious in cold areas. The pathogen can survive in the soil for about 3 years, and stubble for 3 years can effectively control the disease.

[prevention and control methods]

① selects disease-resistant varieties: at present, the disease-resistant varieties commonly used in production are Dianfeng 4, Ludan 10, Quchen 3, Baoyu 7, Haihe 14, Yunrui 1, Yunrui 2, Yunrui 7, Yunrui 8 and so on.

② implements rotation and deep ploughing: continuous cropping for many years is easy to increase the amount of bacteria in the soil and cause serious disease. The practice of rotation for more than 3 years can basically eliminate the harm of bacteria in the soil. Turning deep into the soil and pressing the spores below the sowing layer can reduce the source of bacteria and reduce the disease.

③ early extraction of diseased plants: when the white membrane of the diseased ear is not ruptured, pull out the diseased plant, and take the diseased plant out of the ground and bury it or burn it, so as to prevent the bacteria from falling into the soil.

④ chemical control: this disease is an one-time infection disease in the seedling stage, the use of chemicals to prevent the invasion of bacteria in the seedling stage will effectively control the occurrence of the disease. First, the control effect can reach about 90% when seeds are mixed with 25% trimethoprim or hydroxyrustine at a dose of 0.3%. Corn stalk can also be used as an adhesive to increase efficacy. Second, the use of seed coating agents to prevent diseases. At present, there are many kinds of coating agents in production, which can effectively control diseases and insect pests.

Corn ear rot

Corn ear rot can be divided into many types due to different pathogens, such as Fusarium rot, Aspergillus ear rot, Penicillium ear rot and dry rot caused by Disporium.

[symptom recognition] the ear begins to develop from the top or base, a large area or the whole ear is rotten, the diseased grain is wrinkled, dull and not full, and sometimes pink or gray mycelia are often produced between grains. Some symptoms are only shown on individual or local grains, which are dense with red powdery matter, and the diseased grains are easy to be broken. Some bacteria (such as Aspergillus flavus and Fusarium) produce toxins in the growth process, and the ear rot caused by it can cause dizziness, nausea and vomiting when made into products or directly for human consumption. When infected seeds are used as feed, it often causes vomiting in pigs, and in serious cases, it will cause the death of livestock and poultry.

[pathogenic factors] infected seeds, disease residues and disease residues of other crops can cause disease in the field, and it is easy to cause disease epidemic in rainy years in the later stage.

[prevention and control methods]

First, select disease-resistant varieties, at present, the more resistant varieties are Baoyu 7, Tunyu 7, Yunrui 7, Haihe 14, Qing3, Huidan 4, Dianfeng 4, Yunrui 1, Yunrui 2, Yunrui 8, Ludan 10, Quchen 3, Haihe 2 and so on.

Second, collect diseased bodies, burn them or bury them deeply, and practice 2-3 years of crop rotation.

Third, choose the kind of coating.

Fourth, strengthen field management to achieve robust plant growth and improve disease resistance. Timely control of corn borer, because corn borer is the infection vector of ear kernel rot pathogen.

Fifth, keep ventilated, dry and low temperature during storage.

Corn bacterial wilt

Maize bacterial wilt, which mainly occurs at the end of grain filling, is an explosive and destructive disease, which is easy to cause serious yield loss.

[symptom identification] at the end of grain filling, corn often showed sudden withering and wilting, the leaves of the whole plant were withered and faded, the ears were drooping, the bracts were withered, and the base of the stem was water-immersed at first, and then gradually changed to light brown, and the hand defender felt hollow, which often led to lodging.

[pathogenic factors] first, caused by Fusarium; second, caused by Pythium; third, caused by the compound infection of Pythium and Fusarium. The heavy rain from grain filling to milk stage has an important influence on the occurrence of the disease, and the high water content in the soil is an important condition for the occurrence of bacterial wilt.

[control methods] resistant varieties Tunyu 7, Ludan 10, Yunrui 1, Yunrui 2, Baoyu 7, Yunrui 7, Haihe 14, Qing 3, Huidan 4, Dianfeng 4, Yunrui 8, Quchen 3 and Haihe 2 were selected. Attention should be paid to drainage in cultivation measures.

Maize virus disease

Maize virus diseases mainly include maize dwarf mosaic disease and maize rough dwarf disease.

[symptom identification] Maize dwarf mosaic disease, also known as mosaic stripe disease, can be susceptible to the disease during the whole growth period of maize. At the seedling stage, the green strips appeared at the base of the heart leaf, and gradually extended to the whole leaf. The leaf vein remained green and the mesophyll tissue lost green and turned yellow, forming obvious yellow-green stripe symptoms. Seriously diseased plants cannot bear ears or die ahead of time.

The typical symptom of maize rough dwarf disease is plant dwarfing, the infected corn is dark green, the mesophyll is thick and stiff, and sometimes the heart leaves are curled together and arched as the base continues to grow. There are short raised stripes on the veins of leaves, leaf sheaths and bracts, which are grayish green at first and grayish brown in the later stage. the height of the diseased plant is often less than half of that of the healthy plant.

[pathogenic factors] Maize dwarf mosaic disease can be inoculated by juice friction. It is mainly transmitted by aphids, but the virus transmitted by aphids is not persistent. The virus of this disease can not only harm corn, but also infect sorghum, millet and many kinds of grasses. In the south, the virus can winter with a variety of crop and weed hosts.

Aphids not only transmit virus, but also do serious harm to corn. Aphids often cluster on the back of the male flowers and leaves of corn to suck the juice from the corn tissue and spit out a kind of saliva to inhibit the growth of corn and affect the pollination of corn, resulting in empty buds and baldness.

Corn rough dwarf virus is mainly transmitted by gray planthopper and is persistent transmission. The virus can survive the winter in nymphs of gray planthopper or in wheat seedlings infected before winter.

[prevention and control methods]

First, select resistant and disease-tolerant varieties.

Second, early insecticides kill aphids and gray planthoppers before migrating to cornfields. Spray with 3000 times of oxidizing dimethoate, or spray with 50% aldicarb wettable powder 15 ml 20 g and water 50 mi 75 kg. To kill insects in the corn field, you can use 40% dimethoate emulsion 1 kg, add water 5Mu6 kg, at the base of the stem of the killed corn, use a brush or cotton ball dipped in medicine, smear around the half of the stem, so that you can kill insects through internal suction.

Third, strengthen cultivation management and improve plant disease resistance.

Corn gray leaf spot

[symptom identification] mainly harms maize leaves, but also infects leaf sheaths and bracts. At the initial stage of the disease, a round, oval reddish-brown rectangular spot was formed between the leaf veins. the spot was mostly limited to the leaf veins and parallel to the leaf veins. when it matured, the spot was gray in the center and brown at the edge, with a size of (4mur20) mm × (2mur5) mm. When the humidity is high, the back of the disease spot produces gray mildew.

[pathogenic factors] the disease is caused by fungi. The pathogen mainly overwinters with the remains of corn disease and produces conidia under suitable conditions. Conidia spread with airflow and raindrop splash. After the disease of corn, conidiophores and conidia are produced on the disease spot, and many times of re-infection occur in one growing season.

Most of the diseases began to occur from the lower leaves at the heading stage. The temperature is low (20 ℃-25 ℃), there are many Rain Water, and the atmospheric relative humidity is more than 90%. Grey spot disease occurs seriously, which is easy to cause epidemic, while high temperature and drought restrain the epidemic of the disease.

[prevention and control methods]

① selected disease-resistant varieties: Haihe 1, Haihe 2, Yunrui 1, Beiyu 2, Yunyou 196, Great Wall 799, Baoyu 12, Yuyu 22, Nongda 108, etc., especially Haihe 1 and Beiyu 2.

After the harvest of ② corn, the remains of diseased plants were removed in time, burned or buried deeply, and a large area of rotation was carried out.

③ medicament control: spray prevention in time at the initial stage of the disease, choose 500x solution of 70% methyl thiophanate wettable powder, 50g of 10% high water dispersible agent, 500x liquid of 70% chlorothalonil wettable powder, 68.7% silver turbidite suspension 100ml per mu or 50% carbendazim wettable powder 500x spray. Spray once every 10 days, spray 2 Mel 3 times in a row. The effect of alternating use of several agents is better.

Corn rust

25% triadimefon wettable powder 1500 000 times or 50% sulfur suspension 300 times can be used in the early stage of the disease.

Ground tiger

The ground tiger is also called the ground silkworm, the soil silkworm and the root cutter. There are many kinds of tigers, among which small tigers and yellow tigers are often endangered.

[living habits] the first generation larvae do serious harm to the ground tiger, and the life and harmful habits of each instar larvae are different. The first and second instar larvae move day and night and eat harvested leaves or tender leaves; after the third instar, they hide in the soil during the day and do harm at night, biting off the tender stems at the base of the seedlings, resulting in lack of seedlings; the drug resistance of the fourth instar larvae is greatly enhanced, therefore, chemical control should eliminate the larvae before the third instar.

[Occurrence factors] Rainy autumn is the occurrence and omen of two kinds of cutworms. It is rainy from February to March in early spring and less rainy in April. At this time, when the larvae are just hatched or in the first or second instar, it is beneficial to the occurrence of cutworm, and the first generation larvae may be seriously damaged. On the contrary, from the middle of April to the first ten days of May, there are many rainy days with moderate rain and heavy rainfall, resulting in a large number of deaths of the first and second instar larvae, and the possibility of harm to the first generation larvae is light.

[Control methods] The control of cutworms must take measures combining moth trapping, weeding, pesticides and artificial control.

1 trapping adults: trapping adults is the best way to control cutworms, which can greatly reduce the number of first-generation larvae. The method is to use black light and sweet and sour liquid to trap.

Weed eradication: Weeds are the main place for adults to lay eggs and an important way for larvae to transfer to corn seedlings. Thoroughly eradicate weeds before corn emergence, and timely remove field outsiders feed or compost, do not throw littering. Weed eradication will effectively lower the insect population base.

(3) Pesticide control: after emergence, the average number of insects per square meter was 0.5, which was the suitable period for pesticide application.

4. Seed coating or seed dressing with pesticide: seed dressing with furadan seed coating agent, seed dressing according to 1% of corn seed weight. 50% phoxim emulsion can also be used 0.5 kg water 30-50 kg mixed seed 350-500 kg.

(5) Poisoning soil: 1.5 kg of 3% carbofuran granules or 0.5 kg of 50% methamidophos emulsion per mu shall be mixed with 40 kg of fine soil and spread evenly.

Poison bait trapping and killing: It is better to trap and kill larvae above 4 instars with poison bait. 0.5 kg of 90% trichlorfon with hot water to open, add about 5 kg of water, spray on the fried oil residue (can also be used instead of cottonseed peel) and stir evenly. 4-5 kg of poison bait per mu, spread in the evening.

corn borer

Corn borer, also known as corn borer, is a worldwide corn pest. Corn borer is a polyphagous pest with many host plants. The main crops damaged are corn, sorghum and millet.

[Symptom Identification] Corn borer larvae are boring pests. The typical symptoms caused by corn borer larvae are neat rows of holes in the unfolded corn leaves after the heart leaves are pierced. After the tassel is pulled out, corn borer larvae drill into the male flower and damage it, often causing the base of the male flower to break. After the female ear appears, the larvae transfer to the female ear to feed on filaments and young bracts, bore into the cob axis or eat young seeds. Some larvae bore into the stem from the stem and leaf sheath, feeding on the pith, making the stem easy to be broken by strong wind. The seeds of damaged plants are not full, withered and premature senescence, and some ears even have no seeds, resulting in serious yield reduction.

[Living habits] Corn borer can produce 1-6 generations a year due to different climatic conditions in different places. It overwinters in corn stalks and corncobs as larvae, and some larvae overwinter in weed stems. The occurrence period is extremely irregular, and there is generation overlap.

[Causes]

① insect population base: insect population base is large, often causing serious harm under suitable environmental conditions.

Temperature and humidity: corn borer is suitable for growth and development under high temperature and humidity conditions. The optimum temperature for the growth and development of each insect is 16-30℃ and the relative humidity is above 60%. Corn borer mainly occurs from June to September.

③ Corn varieties: Different corn varieties have great differences in victimization. There is a kind of anti-moth substance Dingbu in maize tissues. The adults lay eggs on maize varieties with high Dingbu content, and the mortality of hatched larvae is very high. Some varieties of corn tissue morphology, can avoid adult eggs and reduce the stem borer damage, such as long and dense hair on the leaf stalk, the stem borer damage is very light.

④ Natural enemies: There are many kinds of natural enemies of corn borer, and Trichogramma has a greater inhibitory effect on corn borer.

[Control methods]

(1) Control in overwintering period: Most corn borer larvae overwintered in corn stalk and cob, and pupated in them in the next spring. Before the end of April, corn stalks and cobs should be burned up as fuel, or crushed as feed, and weeds such as cocklebur should be eliminated for overwintering hosts, which can reduce the number of overwintering insects.

(2) Control at the heart leaf stage: When the rate of mosaic eaten by corn borer reaches 10% at the end of heart leaf, or when the rate of insect ear reaches 5% at the silking stage of summer and autumn corn, it should be controlled. Prevention and treatment methods can be granules and liquid perfusion. 2kg/mu of 3% phoxim granules and 3% furadan granules were mixed with 5 times fine sand to prepare arsenopyrite, which was scattered on the heart leaves of corn. The liquid medicine perfusion method can use 80% dichlorvos emulsifiable solution, diluted into 2500-3000 times solution, each corn plant irrigation 10-15 ml, the control effect can reach more than 85%, at the same time has a concurrent control effect on corn thrips.

(3) Control at ear stage: 0.5 kg of 50% dichlorvos emulsion, 500-600 liters of water, a small middle opened at the top of female ear, injected with a small amount of liquid medicine, 1 kg of liquid medicine can generally irrigate 360 female ears.

Biological control: Trichogramma has a significant role in eliminating corn borers, and the cost is low. Bees are released at the beginning, peak and end of corn borer oviposition, 10,000 - 30,000 bees are released per mu, and 2-4 bee release points are set up. The egg card is rolled up with corn leaves, and the height of the egg card is 1 meter from the ground. In addition, microbial pesticides such as Bacillus borer, 7216 and Beauveria bassiana were used. There are two ways of application: one is to irrigate the heart leaf, with 1 kg of bacterial powder containing more than 10 billion spores per gram and 1000-2000 kg of water, perfusing the heart leaf. Another way is to prepare into bacteria soil or granules, bacteria soil generally with 1 kg of moth killing bacteria plus fine soil or furnace ash 100-300 kg. Granules are generally prepared into about 20 times (1 kg of Beauveria bassiana powder mixed with 20 kg of slag particles), and about 2 g is applied to each plant.

(5) Insect-resistant varieties should be selected.

armyworm

The armyworm is an explosive and destructive pest. Commonly known as cotton locust, army worm, night thief, razor branch worm.

[Symptom recognition] The larvae of armyworm are naked on the surface of plants to feed on harm. The first and second instar larvae mostly hide in the heart leaves or leaf sheaths of crops and feed day and night, but their food intake is very small, gnawing on the residual epidermis of mesophyll, resulting in translucent small stripes. The fifth and sixth instar larvae are in gluttony stage, nibbling leaves and eating cob axis.

[Living habits] armyworm diapause phenomenon, suitable conditions, can be continuous reproduction. They like to lay eggs on the tip of dried seedling leaves and have the characteristics of migration. Larvae have pseudo-death, and their resistance to pesticides increases with the increase of insect age. Armyworm has strict requirements on temperature and humidity. The optimum temperature for adult oviposition is 15-30℃. If it is higher than 30℃ or lower than 15℃, the number of adult oviposition decreases or cannot lay eggs. Migratory armyworm moth encounter wind and rain, forced to land, then the local armyworm harm on the heavy occurrence. However, natural enemies also have a great inhibitory effect on the occurrence of armyworm. The main natural enemies of armyworm are parasitic flies, parasitic wasps, nematodes, ants, walking beetles, red spiders, flower spiders and some fungi.

[Control methods] To control armyworm, moth catching, egg collection and larva killing should be combined. There are three key links to catch and eliminate adults before laying eggs, collecting eggs before hatching, and killing larvae before the third instar.

① trapping adults (moths): trapping and killing with millet straw and sweet and sour liquid. Sweet and sour liquid ratio: sugar 3 parts, wine 1 part, vinegar 4 parts, water 2 parts, mix well. Night traps.

2. Egg attraction and egg collection: use adult oviposition habits to eliminate egg blocks before hatching. From the early stage to the peak period, small millet straw handles were inserted in the field, and sweet and sour wine was sprinkled on the millet straw handles to induce moths to lay eggs. The effect was very good. Picked eggs in time to destroy them.

(3) Chemical control: There are 20-30 insects in 100 plants of maize in seedling stage and 50-100 insects in 100 plants in middle and late growth stage, that is, chemical control. 2.5% trichlorfon powder can be sprayed 2- 2.5kg per mu, or 2.5% trichlorfon powder about 2kg to fine soil 10- 15kg, evenly mixed and then spread along the ridge to prevent old larvae; or 90% trichlorfon 1000-2000 times solution, 50% 1605, 80% dichlorvos 2000-3000 times solution spray, the effect is very good; 2.5% cymethrin emulsifiable concentrate and 20% Sumimedicine 1500-2000 times solution can be used for control.

red spider

Corn spider belongs to mites, also known as fire dragon, fire spider, red sand and so on.

[Symptom recognition] Red spiders generally begin to harm corn after heading, and in early years, they begin to harm corn when it has 6 leaves. Red spider stings crop leaf tissue nutrients, so that the injured leaves present dense small yellow-white spots, then gradually turn green to yellow, and finally dry and die. The damaged corn grain is thin, resulting in reduced yield.

[Living habits] The adults of corn spider hide in the rhizosphere soil cracks for winter. After the temperature rises in early spring, red spiders emerge and concentrate on some weeds to feed and reproduce. After spring corn emerges, they transfer to nearby corn seedlings through wind blowing and crawling. Red spider in the field was point-sheet damage, from the insect source to spread to the whole field of corn, after a long time. After heavy rain, the number decreases, and drought and little rain, the number increases.

[Control methods]

① Eliminate overwintering adults: Irrigation in early spring and autumn can eliminate a large number of overwintering red spiders.

(2) Chemical control: 40% dimethoate emulsion and 20% dicofol mixture (1:1) 1000-1500 times, the effect is very good.

(3) Natural enemies: The natural enemies of corn spider include ladybug, thrips and lacewing.

aphids

Aphid reproduction and general pests are different, with parthenogenesis and sexual reproduction alternate characteristics, so its life history is more complex, often appear several generations "same hall", one year can occur more than 20 generations, insect density is very large, damage time is long, the loss caused to corn is also serious.

[Control methods]

① Chemical control: spray with 3000 times solution of 40% oxidation happy fruit; or spray with 50% anti-aphirimidine wettable powder 15- 20g mixed with 50- 75kg water. In corn field pest control, can use 40% dimethoate emulsion stock solution 1 kg, add water 5-6 kg, in the injured corn stem base, with a brush or cotton ball dipped in medicine daub, the stem half node around are coated, good through internal absorption pest control.

(2) Use of natural enemies: The natural enemies of corn aphids are mainly aphidids.