Cotton bollworm

Scientific name Helicoverpa armigera (Hubner) Synonyms Heliothis armigera Hubner is Lepidoptera, Noctuidae. Alias ​​cotton bollworm. Widely distributed in China and around the world, China's cotton and vegetable growing areas have occurred. The cotton area suffers heavy losses in the Yellow River Basin and the Yangtze River Valley. The worm is a dominant species in the budding period pests in China's cotton planting area and has been extremely destructive in recent years.

In addition to harming cotton, the host also harmed corn, sorghum, wheat, rice, tomatoes, kidney beans, peas, sorghum, halva, sesame, sunflower, tobacco, and peanuts.

When damage is caused by cotton, the larvae damage the young leaves into nicks or holes; after damaging the cotton buds, the pods turn yellow, the lower part of the buds are boring holes, and the diameter is about 5mm. They are not round, there is no feces in the buds, and the buds are granular outside. Faeces, buds and lobes opened into yellow-brown, 2-3 days after shedding. When Qingling suffers, the base of the bell is bored, the hole is thick, and it is nearly round. The excrement piles out of the borehole. The auburn is brown. The bell is fed with one or more compartments of cottonseeds and fibers, uneaten fibers and seeds. Water stains, into a rotten bell. One larvae often harmed more than a dozen bells, and severe bells shed more than half.

Morphological characteristics Adult body length 14-18mm, wings 30-38mm, gray-brown. The front wing has brown ring pattern and kidney pattern. There are two brown lines on the front vein in front of the kidney pattern. The outer side of the kidney pattern is a brown wide band with black spots on each side of the vein. The hind wings are yellow-white or light brown and the end areas are brown or black. Eggs about 0.5mm, hemispherical, milky white, with a vertical and horizontal grid. The cooked larvae have a body length of 30 to 42 mm, and their body color changes greatly from light green, reddish to reddish brown and even to dark purple, common types are green and red brown. The head is tan, with dark vertical lines on the top, backline, and valve lines. The valve is white, and the metatarsal hooks are the middle and double bands. The connection of the two anterior thoracic hairs (Ll, lz) is tangent or intersects with the lower end of the thoracic valve. The body surface is covered with small thorns and its base is larger. Long 17-21mm, brown. There are 7-8 rows of semicircular engraved points on the abdomen of the abdominal section 5-7, and 2 hooks of the hip spines.

Life style Liaoning special early mature cotton area and Northwest inland cotton area 3 generations per year, North China and Yellow River basin 4 generations, Yangtze River valley 4-5 generations, South China 6-8 generations, with diapause eels in the soil Wintering. The overwintering adults of the Yellow River Basin have been seen in late April. The first generation of larvae mainly damaged wheat, peas, flax and vegetables. The wheat fields accounted for 70-80% of the total. The second generation of adults began to appear in the middle and early July and the middle of July. In the late days, the main damage to cotton was very concentrated, accounting for 95% of the total. In the third and fourth generations, besides harming cotton, they also harmed corn, sorghum, peanuts, beans, and tomatoes. The amount of insects was relatively dispersed, accounting for 50-60% of the cotton fields. The three generations of adults began to appear in the middle and early August, and they took a long time. Four generations of adults in the Yangtze River Valley have been seen in the middle and early September. Cotton entered the bud stage in June. The eggs of the first generation of cotton bollworm were mainly produced in the heads of cotton plants and the young leaves. The buds in the early growing fields had more eggs, and the eggs were heavy and the victims were heavy. The second-generation adults prospered in July and early August. The eggs were laid on the top leaves of the cotton plants, on the tender leaves of the marginal heart, and on the tender bud leaves. There were many buds, more vigorously growing eggs in the cotton fields, and three generations of adults in August. In the middle and late of the year, the eggs were sparsely distributed on tender buds and tender bells. The three generations took a long period of time, occurred in large quantities, and later prospered and later became heavy in cotton fields. Adults lay their eggs at night for mating. Each female lays an average of 1,000 eggs. The egg development period is 15°C for 6-14 days; 20°C for 5-9 days; 25°C for 4 days; 30°C for 2 days. The newly hatched larvae hatched the eggshells and began to infest the growing point and feed on the young leaves the next day. On the fourth day, they were transferred to young larvae and bored. After the 2nd instar larvae entered the tender buds to take in the flower buds. 3-4 instar larvae mainly damage buds and flowers, causing budding, 5-6 years into the gluttony period, mostly harming bells, big buds or flowers, injuring the bells from the base foraging, large pods, and insects outside the hole. Large and numerous grains, larvae have the habit of turning the bell, when the damage to Lei Ling bell, the latter part of the body stays outside, the entire larvae period can damage more than 10 buds, flowers, bells. Cloudy old larvae often suck their flowers in flowers, and young larvae often kill each other. Most of the larvae were 6 instar, 5 instar or 7 instar, and the larvae developed at different temperatures: 31 days at 20°C, 22.7 days at 25°C, and 17.4 days at 30°C. The mature larvae in the 3-9cm topsoil in the soil-building room, the soil chamber has a protective effect, when the emergence of adults along the original road after climbing out of the soil surface after the wings, winter plowing winter irrigation damage the soil, affecting the emergence rate.

The developmental duration of earthworms: 28 days at 20°C, 18 days at 25°C, 13.6 days at 28°C, and 9.6 days at 30°C. H. armigera is a thermophilic and wet-fighting insect. The optimum temperature for adult oviposition is above 23°C, and spawning is rarely performed below 20°C. The development of larvae is most suitable at 25-28°C and relative humidity 75-90%. In the north, the influence of humidity is more significant. The monthly drop is more than 100mm, and the relative humidity is more than 70%. However, excessive soil formation caused by excessive rainfall is not conducive to the larvae's invading earthworms while increasing their mortality. In addition, heavy rain can wash out the eggs of H. armigera and also have inhibitory effects. Adults need to eat on honey plants for nutritional supplements. In recent years, cotton bollworms have become increasingly harmful to cotton. Main reasons: First, the changes in planting structure and the continuous improvement of water and fertilizer conditions in cotton fields have provided a suitable environment and suitable food for each generation of bollworms. Second, the reduction of spring corn area, increase in tomato cultivation, adequate water and fertilizer in wheat, improved the habitat of a generation of cotton bollworm, accelerated the growth rate, and provided a large number of insect sources for the second generation in cotton fields. Thirdly, the increase in cotton intercropping area is very favorable for the occurrence of the fourth-generation cotton bollworm, which provides more insect sources for the occurrence of bollworm in the following year. Fourth, the comprehensive prevention and control measures based on chemical defense have long been unable to keep up, resulting in a rapid increase in drug resistance, and natural enemies were killed and wounded, reducing the natural control effect. In addition, weather conditions that are suitable for the occurrence of cotton bollworm can cause damage to the bollworm. The optimum temperature for breeding H. armigera is 25-28°C and relative humidity is 75-90%. The number of rains during cotton damage is large and the rainfall is evenly distributed. The cotton fields in the arid area where the irrigation is timely or where the water and fertilizer conditions are good and the growth is strong, the cotton field where the former is wheat or green manure and the cotton and cotton adjacent to the cotton field are favorable for the occurrence of the cotton bollworm. Natural enemies include more than 60 species such as Trichogramma, T. urticae, T. arborea, I. japonicus, fly, spiders, grasshoppers, ladybugs, cockroaches, and florets.

Prevention and control methods (1) Mid-term and short-term predictions in the south From the middle of May, in the middle and late May of the year, random selection surveys or sweeping methods were used to investigate the number of native bollworms and the age of larvae, compared with previous years. The second generation of cotton bollworms in cotton fields. In the short-term report, according to the time and quantity of black eggs and poplar branches attracted to previous generations of adults and fields to find contemporary eggs, the occurrence period and amount of contemporary larvae are forecasted to guide the prevention and control of production. (2) Appropriate planting of medium-planted 372, national anti-95-1 and other gene-resistant insect-resistant cotton, proper late-planting of short-season cotton, try to avoid second-generation cotton bollworm, use of poplar branches to attract moths, planting 300-500 strains in cotton fields Crop moths such as corn or sorghum come to lay eggs, concentrate on killing, and do everything possible to reduce the amount of eggs deposited by the cotton plants. After the wheat is harvested, the cultivars are promptly cultivated to eradicate some generations of earthworms, and the number of insects is reduced. Combine pruning in the field in time to top, remove the side of the heart and ineffective buds, and bring it to the field to focus on processing. July-August combined with cotton top dressing, spraying 1%-2% superphosphate calcium leaching solution on the cotton plant, can reduce the amount of eggs. (3) Wheat intercropping areas should pay attention to the selection of early maturing varieties of wheat and cotton. The requirements for wheat should be advanced by 10 days. Cotton varieties should be selected to suit the planting pattern in order to worsen the food sources of the first and fourth generation bollworms. When cutting cotton, attention should be paid to oming eggs and larvae, which can effectively reduce the source of insects. (4) Biological control In the first hatching period of the second-generation cotton bollworm, 1.5 to 20,000 Trichogramma per 667m2 were released, the egg parasitism rate was over 70%, and Bt containing more than 10 billion spores per gram could also be sprayed. Emulsion 400ml, once every 3 days. It can also release 5000-6000 heads of grasshoppers, and can also spray biological insecticides such as cotton bollworm virus and 7216 to control newly hatched larvae, and at the same time pay attention to the protection and utilization of other natural enemies. Do everything possible to reduce the second generation of cotton bollworm base. (5) Large-area high-pressure mercury lamps are to be installed. One 300W high-pressure mercury lamp per 667m2 is installed. The lamp is filled with water in a large container and the surface of the water is filled with diesel oil. The effect is several times higher than that of a black light lamp. (6) When the cotton bollworms of the second and third generation reach the prevention and control index, the yield of cotton is 90kg per 667m2, the accumulated eggs of the second generation of cotton bollworm are 250 eggs, or the accumulated eggs of the second cotton bollworm is 75kg per animal in the cotton field of 667m2. 150 grain, 667m2 production lint 50kg low-yield cotton fields and the above three generations of high, medium and low yield cotton fields, when the accumulated egg quantity of 80 grains, should be immediately prevented. The key is to catch the hatching period of eggs until the 2nd instar age. The larvae will be sprayed with 10.8% Caesar EC before each bell, 80ml for every 667m210-15ml or 32.8% for cotton, and 80ml for 42% Triak EC. %Saidan EC 100-130ml, 40% Huifeng No. 1 EC50kg per 667m 250ml water, 2.5% Uranus EC 3000 times. As far as possible without or with pyrethroid pesticides, to prevent the vulva up. The control of the fourth generation of cotton bollworm can also be used 1.8% of farmhouse music (avermectin B1) 4000-5000 times or 30% of linghuawei EC 1500 times, 40% of the anti-ringbellose oil 1000 times, 10% imidacloprid Wettable powder 1500 times, 20% methomyl EC 1500 times, 35% SF No. 2 EC 1000 times, 2.5% Cyanocyanine EC 1500 times, 20% Agriculture Lubricant EC 1500 times, 20 % of insecticide net WP 2000 times, 45% propionicin EC 1500 times, 43% chlorinated chlorinated EC (New Braun) 1500 times (Beijing Shunyi Pesticide Factory), 44% of Speed ​​Cay's 1500 times, 50% Caiming No. 2 EC 1000x is effective against resistant bollworms. Pay attention to alternate rotation of drugs, in the high temperature season continuous dose of methomyl, phoxim is prone to injury when the amount of liquid spray per 667μm is 100L. (7) Key technologies for the control of cotton bollworm application 1 Older pesticides such as methomyl, methyl parathion, isocarbophos, methamidophos, cypermethrin have better protection against bollworm eggs and young larvae. Effective, but because of the longer time spent on production, some have developed resistance, but they can still be used interchangeably or mixed. Do not use it continuously. However, methamidophos is highly toxic and has been banned in Shanghai. Other areas should be phased out. Methomyl has an outstanding effect of killing eggs, but high concentrations are not safe for cotton, and can be used in combination with aqueous amifenphos, cypermethrin, endosulfan, etc., and use its good killing effect. Insecticides have been used to control the cotton bollworm, but have been banned. At present, the promotion of the use of 40% water phosphathiophosphate, 50% parathion EC 2000x, and 43% Chlorocyanine 1500x liquid has higher virulence to eggs and larvae of Helicoverpa armigera and can completely replace the insecticide. 244% Profenofos EC, 75% Lavein EC, and 35% SAID (Endosulfan) EC have good control effect against Helicoverpa armigera and have a long residual effect period, but their cost is high and should be used according to their characteristics. For example, Ravelin and endosulfan are safer for natural enemies, and the use of large quantities of natural enemies in the field can kill fewer natural enemies and exert biological control. 44% proropochlor EC has good control effect on cotton bollworm, cotton leaf aphid and cotton aphid. It can be used to prevent and control three generations of cotton bollworm, cotton aphid and cotton leaf aphid, and can receive multiple effects with one drug. 2 The effect of monocrotophos control of cotton bollworm is very poor, but 40% of monocrotophos EC can be used 150 to 200 times the heart of the droplet to prevent and treat the second-generation bollworm. Phoxim and its blends are mainly based on contact toxicity and have a short residual period. They should not be used during the egg period. They are suitable for later eradication and can be mixed with other pharmaceuticals if necessary. As the older larvae are hidden, the prevention and control are more difficult. Therefore, the prevention and control of the larvae should focus on ovicidal and cotton instars before the 2nd instar, swept 1-2 times, if necessary with 5% fluvoluril, 150ml/water per 667m2. 75kg, better than cypermethrin. It is also possible to use a 30% solution of dioxin EC (Mordovir 10 phoxim) 1000 times. There are many agents for the control of cotton bollworm, such as linglingling, killingweiwei, yudodan, insecticidal king, and fruit cotton, etc., which are effective agents for controlling resistant bollworm. In addition, cotton boll treasure, Xincyan EC, North agricultural 931, etc. also have a high control effect on the cotton bollworm, all localities can be selected according to local conditions. The key is to grasp the best medication time and the correct application site and rational application methods. The worms infested the growth site on the second day after hatching. On the fourth day, they were transferred to young larvae and damaged. They were very sensitive to pesticides and were the key period for drug control. The production of a pair of cotton bollworms, such as egg volume Large, aggressive, should start medication from the beginning of the egg, such as the best effect when the 50% of the eggs began to darken. For the second generation of cotton bollworm, when the accumulated egg quantity of 100 cotton plants reaches 100 grains, the medicine can be used for prevention and treatment. The third and fourth generations of cotton bollworms can be used when the number of accumulated eggs in one hundred plants reaches 25 or 5 larvae. The eggs of the second generation of Helicoverpa armigera are most prolific on the top leaves of cotton plants. The top of the cotton should be protected during spraying, and the medicine should be sprayed on the top leaves. The third and fourth generations of cotton bollworms often produce eggs on the side of the leaves. Should be sprayed on the tip of the group to protect the young buds from harm or less victimization.