Corn armyworm damage Corn armyworm control technology points

Today I will introduce to you the symptoms and prevention methods of corn armyworm:

Corn Armyworm Introduction

Corn armyworm: (Mythimnaseparata walker) belongs to the Lepidoptera, Noctuidae, also known as armyworm, shaving insect, and five-color insect.

Larvae: There are black stripes on the top of the larvae's head, and the head is brown, yellowish brown or reddish brown. The 2nd to 3rd instar larvae are yellowish brown to grayish brown, or dark red, and the 4th instar and above are mostly black or grayish black. There are five dorsal lines on the body, so it is also called the five-color insect. There are black-brown stripes on the outside of the abdominal foot, and there are obvious white lines on the spiracles. The pupa is reddish brown.

Adult: 17-20 mm long, light gray-brown or yellow-brown, with the male moth being darker. There are two khaki round spots on the forewings, with a small white spot below the outer round spot, and a small black spot on each side of the white spot[1]. There is a dark brown diagonal stripe at the top corner of the wing.

Eggs: Bun-shaped and slightly shiny, white when first laid, gradually darkening in color, and turning black when about to hatch.

Key points of corn armyworm control technology

Larvae control requires universal control in areas with high incidence, and general occurrence areas require timely selection and treatment.

Corn armyworm is a long-distance migratory pest that migrates from southern provinces to our province every spring to harm wheat in the jointing and heading stage. In late May, the armyworms that occurred in our province migrated to northern my country and caused damage. In autumn, as the temperature drops, the corn armyworms that occurred in northern regions migrate back to the south with high-altitude air currents, and some of them may migrate to the corn-producing areas of our province, posing a certain threat to our autumn corn production. Since mid-to-late July this year, corn armyworms have occurred in large areas of corn fields in Northeast my country and North China. It is expected that some of the third-generation armyworms that occurred in northern corn-producing areas from late August to early September may migrate to corn-producing areas in our province, forming the insect source base for the occurrence of the fourth-generation armyworms in our province. This year, the sowing period of summer corn in our province is long, the growth period is uneven, the food conditions of medium-to-late-maturing summer corn and the autumn climate conditions are conducive to the occurrence of the fourth-generation armyworms. It is expected that there will be a moderate possibility of the occurrence of medium-to-late-maturing summer corn armyworms in our province, and the peak period of young larvae is expected to occur in early to mid-September.

The technical opinions suggest that for adult control, we should take advantage of the phototaxis and chemotaxis of adult sticky insects, and use pollution-free control technologies such as sweet and sour liquid, sex traps, and insecticidal lamps to lure and kill adult insects, so as to reduce the amount of eggs laid by adults and reduce the insect population density in the field. The control time for larvae is early to mid-September in most parts of the province, and the control target fields are medium-to-late summer corn fields. The control target is a corn field insect population density of 30 heads per 100 plants. For control, use 75-100 grams of 50% zinc sulfide emulsifiable concentrate, or 75-100 grams of 40% chlorpyrifos (chlorpyrifos) emulsifiable concentrate, or 500-1000 times diluted 20% chlorpyrifos suspension No. 3 per mu, and spray evenly with 40 kg of water. [2]

Corn armyworm damage

Corn borer larvae feed voraciously on corn leaves. In severe cases, they will eat up all the leaves in a short period of time, causing a reduction in yield or even a total crop failure. The main symptom of damage is that the larvae bite the leaves. The 1st to 2nd instar larvae feed on the leaves and cause holes. The 3rd instar and above larvae damage the leaves and leave irregular notches. When they are voracious, they can eat up all the leaves. In severe cases, they will eat up all the corn leaves, leaving only the veins, causing a serious reduction in yield or even a total crop failure. When all the corn in one field is eaten up, the larvae often move in groups to another field to cause damage, so they are also called "marching insects." Generally, fields with low terrain, uneven corn plants, and overgrown weeds are severely affected.

Corn Armyworm Causes

There are many precipitation processes, and the soil and air humidity is high. The meteorological conditions are very conducive to the occurrence of cornworms in summer corn fields. The recent survey results of the Shaanxi Meteorological and Agricultural Remote Sensing Center show that cornworms mainly occur in Linwei District, Pucheng County, Fuping County, the five northern counties of Xianyang, and parts of Shangluo. According to the latest monitoring results of the Provincial Plant Protection Station, the area of ​​cornworms in the province is 3.75 million mu, of which 670,000 mu are severely affected, and the rate of damaged plants is about 80%. For this reason, the meteorological department has issued a forecast of suitable conditions for spraying. Most areas of the province are more suitable for spraying operations in the short term in the future, and the eastern part of Guanzhong is suitable for spraying operations. Cornworms are migratory pests that migrate from the Yangtze and Huaihe River basins and cannot overwinter in Shaanxi. Therefore, they are characterized by sporadic and explosive occurrences.

Corn armyworm growth

Corn armyworm is an omnivorous and voracious pest. It is the most serious harm. It occurs and harms to varying degrees in all parts of my country. 1 Symptom identification Borers and cutworms belong to the same family of pests, Noctuidae. Their life cycle is divided into four stages: adults, eggs, larvae and pupae. The larvae of cutworms are exposed on the surface of plants to feed and cause harm. The 1st and 2nd instar larvae are mostly hidden in the heart leaves or leaf sheaths of crops, feeding day and night, but the food intake is very small, and they gnaw on the remaining epidermis of the leaf flesh, causing small translucent stripes. The 5th and 6th instar larvae are the voracious stage, eating leaves and cobs. 2 Morphological characteristics Adults are light gray or light yellow-brown, female adults are 18-20 mm long, and male adults are 16-18 mm long. The eggs are hemispherical and shiny, and are laid in the wrinkles at the end of dead leaves or young leaves of plants. The newly hatched larvae are gray-brown, and when the 2nd and 3rd instar larvae feed on young leaves, the front or most of the body is green or gray-green. The mature larvae are 38 mm long, with reddish brown heads, reticulated skulls, thick brown longitudinal stripes on both sides, slightly in the shape of a figure eight, and brown reticulated outer sides. The body color varies greatly from light green to dark black. In large outbreaks, the back is often black, the ventral surface is lightly dirty, the midline of the back is white, and there is a slight bluish tint between the subdorsal line and the upper line of the spiracles. The pupa is about 20 mm long, reddish brown, and shiny. 3 Occurrence rules There is no diapause in the insects, and they can reproduce continuously as long as the conditions are suitable. The number of generations and the period of occurrence vary depending on the region and climate. From north to south in my country, 2 to 8 generations can occur in a year.

Morphological characteristics of armyworms

The adult body length is 15-17mm, with a wingspan of 36-40mm. The head and chest are gray-brown, and the abdomen is dark brown. The forewings are gray-yellow-brown, yellow or orange, with many variations; the inner horizontal line often has only a few black spots, the ring and kidney pattern are brown-yellow, with no obvious boundaries, and the kidney pattern is

There is a white spot at the rear end, with a black spot on each side; the outer horizontal line is a row of black spots; the submarginal line is inclined from the top corner to Mz; the marginal line is a row of black spots. The hind wings are dark brown, gradually fading towards the base. The eggs are about 0.5mm long, hemispherical, white at first, gradually turning yellow, and shiny. The eggs are arranged in a single layer in rows and blocks. The mature larvae are 38mm long. The head is reddish brown, the skull has a reticulate pattern, the forehead is flat, there are brown coarse longitudinal stripes on both sides, slightly in the shape of an eight, and there are brown reticulate patterns on the outside. The body color varies greatly from light green to dark black (often due to different food and environment); when it is in full bloom, the back is often black, the ventral surface is light and dirty, the dorsal midline is white, the subdorsal line and the upper valve line are slightly blue, and the valve line and the lower valve line are pink to grayish white. There is a dark brown wide longitudinal band on the outside of the abdominal foot, and there is a semi-circular dark brown toe hook at the tip of the foot. The pupa is about 19 mm long and reddish brown. The front edge of the back of the 5th to 7th abdominal segments is marked with a row of serrated dots. There are four spines on the anal spine, the two in the middle are thick, and the thin and short spines on both sides are slightly curved. [5]

The natural enemies of sticky insects disappear.......

Liaoning Province has suffered a serious third-generation armyworm disaster, with a density and distribution range rarely seen in the past 20 years. As of the 12th, the affected area of ​​crops in the province exceeded 2 million mu.

In view of the severe prevention and control situation, the Liaoning Provincial Party Committee and the Provincial Government attached great importance to it and required the province to organize in a unified manner and take scientific pest control measures in a timely manner to minimize the losses caused by pests and resolutely prevent the spread of pests. They also decided to allocate RMB 10 million in special pest control funds. Large-scale prevention and control actions have been carried out in various parts of the province, and a large number of personnel have been organized to carry out dragnet surveys, issue early warnings in a timely manner, and dispatch more than 14,000 people and nearly 8,000 pieces of machinery and equipment to the front line for prevention and control, with a daily prevention and control operation area of ​​more than 700,000 mu.