Corn borer and corn armyworm are the two major pests of corn. The two pests often occur at the same time in corn fields and harm corn. They both belong to the order Lepidoptera, but they harm corn in different ways. Now they will The distinction between corn borer and corn armyworm is introduced as follows:
1. Types of pests
Corn borer: It belongs to the order Lepidoptera, the family Boreridae, and is commonly known as core borer.
Corn armyworm: It belongs to the order Lepidoptera and the family Noctuidae. It is also known as marching bug, razor bug and five-color bug.
2. Morphological characteristics
1. Larvae
Corn borer: Mature larvae are 20-30mm long, cylindrical, with a dark brown head and color on the back. There are many kinds of light brown, dark brown, gray and yellow, etc. There are 4 hair tumors on the back of the middle and posterior chest. There are two rows of hair tumors on the back of abdominal segments 1-8, two on the front and back, and 3 missing rings on the abdominal toe hook. .
The pupa is 15-18 mm long, yellowish brown, long spindle-shaped, with 5-8 stinging hairs on the tail end.
Corn armyworm: The larvae have a figure-eight black stripe on the top of their head, and the head is brown to reddish brown. The 2nd to 3rd instar larvae are yellowish brown to grayish brown, or dark red, and there are many larvae above the 4th instar. Is black or gray-black.
There are five dorsal lines on the body, so it is also called the five-color insect.
There are dark brown lines on the outside of the abdominal legs, and there is an obvious white line on the spiracle.
Pupa is reddish brown.
2. Adult moths
Corn borer: The adult moth is yellowish-brown. The male moth is 10-13 mm long, with a wingspan of 20-30 mm. The back of the body is yellowish-brown, and the end of the abdomen is thin and pointed. , the antennae are filamentous, grey-brown, the forewings are yellowish-brown, with two brown wavy horizontal stripes, and two short yellowish-brown stripes between the two stripes, and the hindwings are greyish-brown; the shape of the female moth is similar to that of the male moth, lighter in color, and the forewings Bright yellow, light brown lines, light yellowish brown hind wings, and fat belly.
Corn borer adult
Corn armyworm: The adult body length is 17-20 mm, light gray brown or yellowish brown, and the male moth is darker.
There are two khaki round spots on the forewing, a small white spot below the outer round spot, a small black spot on both sides of the white spot, and a dark brown diagonal stripe on the top corner of the wing.
Corn armyworm adults
3. Eggs
Corn borer: The eggs are flat and oval, with several to dozens of eggs forming egg masses, arranged in a fish scale shape. It is milky white at first and gradually changes to yellowish white. Before hatching, part of the egg is dark brown (the head of the larvae, called the blackhead stage).
Corn borer eggs are milky white at first
Corn borer eggs
Corn armyworm: eggs are slightly shiny in the shape of a steamed bun, white when first laid, and gradually deepen in color , black when nearly hatching.
Armyworm eggs are about to hatch
4. Pupa
Corn borer: Pupa is 15-18 mm long, yellowish brown, long spindle-shaped, with spines at the tail end 5-8 hairs.
Corn armyworm pupa
Corn armyworm: The pupa is reddish brown and shiny, with a row of tooth-like stipples on the front edge of the back of segments 5-7 of the abdomen.
Armyworm pupae
3. Harm characteristics
Corn borer
Damage caused by mature larvae of corn borer
Corn borer can damage the above-ground parts of corn plants during various growth stages of corn, feeding on leaves, ears, and tassels.
Most of the larvae are in the fifth instar. Before the third instar, they mainly move and feed on the young heart leaves, tassels, bracts and filaments. After the damaged heart leaves expand, many horizontal rows of small holes appear; After the fourth age, most of them are drilled into the stem.
The harm caused by corn borer is mainly because the photosynthetic efficiency of the leaves will be reduced after being eaten by the larvae; the tassels are often easily broken and pollination is affected; the bracts and filaments are eaten, which will cause Missing grains and grains; after the stems, stalks, and cobs are eaten by borers, tunnels are formed, which destroys the transportation of water and nutrients in the plants, increases the rate of stem folding, and decreases grain yield.
Corn armyworm
The larvae of the corn armyworm voraciously eat corn leaves. When severe occurrence occurs, the leaves will be eaten up in a short period of time, resulting in reduced yield or even no harvest.
The main symptom of damage is the larvae biting 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 cause irregular nicks. When they eat too much, they can eat all the leaves.
When it occurs in large quantities, the corn leaves will be eaten away, leaving only the veins, resulting in severe yield reduction or even no harvest.
When the corn in one field is eaten up, the larvae often move to another field in groups and cause damage, so they are also called "marching insects".
Generally, fields with low terrain, uneven height of corn plants, and overgrown weeds are severely affected.
Only by mastering the morphological characteristics and damage characteristics of corn borer and corn armyworm can we take effective measures to prevent and control the occurrence of corn borer and corn armyworm, protect corn from their harm, and improve corn quality and yield. purpose.