Scientific Name: (Helicoverpa Zea)
Corn earworm is Lepidopteran of the genus Helicoverpa in the family Noctuidae larval stages are the worst damaging agricultural pest throughout the world except for Alaska and northern Canada. It was placed in the genus Heliothis and owns very diverse names in different areas of the world. The most common are the American bollworm, cotton bollworm, and tomato fruit worm. However, it feeds on the foliage of economically important crops. Most corn earworms remain active throughout the growing season and select their feeding sites according to the crop development stages. They feed on the inflorescences besides corn ears, cotton bolls, tomato fruit, and pods in pulses crops. Corn earworm is very difficult to prevent and needs specialized techniques to control crops once its threshold crosses the economic injury levels. However, Integrated Pest Management (IPM), and several cultural practices may help to reduce its widespread infestation.
Origin and Distribution
The corn earworm is a pest of temperate and tropical areas in North America and originated from the same regions except for Alaska and northern Canada since both don't allow them to overwinter. Moreover, corn earn populations in the eastern US can't overwinter. They are found in Virginia, Ohio, Kansas, and southern New Jersey, where extreme cold hinders their population. The Corn earworm moths often drift to northern areas depending on the weather conditions. Their northward drifting continues in summer while summer rains and storms could inflict their infestation. Their seasonal migration towards northward determines the severity of infestation. However, the migration varies every year, and a sudden infestation could damage early corn. They are also prevalent in South America besides their spread in most cotton and corn growing areas in China, Africa, Asia, and MENA.
Corn Earworm- Identification
The eggs are light green when deposited and become yellowish, and grey around hatching. Eggs shape is also variable from a dome to a flattened sphere, and it could measure about 0.6 mm long. A female can lay up to 3000 eggs till she remains fertile, and these eggs can hatch within four days. Upon hatching, the larvae feed together, but Individual larval feeding is common when seen in corn ears. The larvae have orange heads, black thorax, and black bodies. Their body color also varies and is often found in green, brown, pink, and yellow with microspikes. A mature larva can measure up to 1.5 inches and mid-dorsal with lines. Prolegs hooks form a straight line, and they exclusively feed in the ear tip zone, entering through the silk channel.
Corn Earworm- Lifecycle
The Corn earworms may remain active in tropical and subtropical zones throughout the year. Often the migratory moths arrive in northern states in mid to late summer that host hardly one generation a year. The number of corn earworms generations increases southwards as two to three in Maryland, northern California, and central Great Plains, 4 to 5 in southern California and Louisiana, and 7 in southern Texas and southern Florida. The complete lifecycle is achieved in 30 days. The larvae may have six instars, and each of them takes an average of 2.9 days to complete. The six instars can be completed in about 13 to 32 days at 68 to 93.0°F, respectively. Mature larvae stop feeding and drop to the ground, prepare chambers, and pupate for 10 to 25 days which is also temperature-dependent. Meanwhile, a pupa gains a length of 22 mm. After that, they develop wings and make nocturnal flights, migrate, and lay eggs for 3 to 4 days on the corn silk. A single female can lay up to 35 eggs per day and about 3000 throughout her life.
Symptoms and Types of Damages
The corn earworm larvae feed voraciously on silks initially and disrupt pollination while gaining access to the kernels. Primarily, the larvae feed at the tip and extend their damage to the mid of the ear. If silks are not available, the larvae could bore into the ear deeply. An individual larva often damages a single ear, and sometimes it leaves the first ear for another. The larvae also feed on the whorls in late-planted sweet corn cultivars. If corn plant is not available, they would feed on alternate host plants that include tomatoes, pumpkins, squash, beans, tobacco, and cotton. The damage is primarily inflicted on fruits, bolls, and pods besides buds and blossoms.
Where Does the Corn Earworm Come from?
The larvae of the Corn earworms happily feed on garden plants when the surface temperatures range between 68 to 93.0°F in summer. Do look them on blossoms, silks, buds, bolls, pods, and fruits depending on the types of plants in your garden.
How to Prevent Corn Earworms?
Corn Earworms- Control
Biological Control
Nature's Good Guys, 500-Minute Pirate Bugs
Minute Pirate Bugs are Orius insidiosus which is a species of flower bugs. Minute Pirate bugs feed on plants damaging pests, including their eggs and the larval stages. These are not the corn earworms that the gardeners control with Minute Pirate bugs. But, they provide excellent control over many soft-bodied insects and bollworms larvae. Orius insidiosus females lay eggs inside the plant tissues. They hatch and are ready to prey in about 20 days. It is possible to have their several generations during one cropping season. Both nymphs and adults feed on the eggs and larvae of corn earworms. Orius insidiosus insert their beak into the victim's body and puncture them leaving behind their skeleton only. They are voracious eaters and can easily locate them to prey.
- Great enemies to all stages of thrips!
- Enemies to aphids, thrips, whiteflies, mealybugs, mites, scale and other soft body slow moving insects
- Can be used indoors and outdoors!
One live Minute Pirate bug feeds on about 80 live larvae or eggs of corn earworms per day.
Good Bugs - Ladybugs
Lady Bird Beetles also feed on many soft-bodied and slow-moving pests, especially the larval stages of different caterpillars. They provide excellent control during the first three instars of larvae development which are often more damaging stages than the rest of their lifecycle. When live bugs or eggs are released in the garden, ladybugs lay eggs on the surfaces of the leaves. The eggs hatch and the beetle larvae become ready to feed on corn earworms larvae in 7 to 10 days.
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Release them in the garden after washing the surfaces of the leaves with splashing water. Never apply if some insecticide is sprayed on the foliage of the plants. About 1500 live bugs can effectively control corn earworms in 1000 square feet.
Organic Control
Southern Ag- Thuricide (Bt), 16oz
If the gardeners need a more quick solution for what they’re looking to control Corn Earworms in home gardens, Thuricide is an excellent product that contains 98.35% of Bacillus thuringiensis, which is a soil-dwelling bacterium and exists naturally on many organic surfaces. Bacillus thuringiensis spores produce Cry proteins which are highly toxic and rupture the midgut of corn earworm larvae. The larvae which ingest Basillus thuringiensis spores can't survive and die within 24 hours of application. Thuricide (Bt) remains active for all stages of corn earworms. However, their slow-moving initial instars get more effectively killed. Also, these initial instar larvae are more devastating than the later stages.
- Size: 16 OZ
- Thuricide BT Caterpillar Control concentrate is used by organic gardeners and is made from bacteria that is toxic to listed pests.
- Safe to use on all plants, vegetables and edible crops.
Mix 4-teaspoons of Thuricide (Bt) concentrate per gallon of water and apply thoroughly on the foliage of the plants.
Bonide - Captain Jack's Dead Bug 
Captain Jack's Dead Bug contains Spinosyn A, and Spinosyn D, which are the chief ingredients of Spinosad that derive from a bacteria, Saccharopolyspora Spinosa, that exist naturally in soil. Spinosad contains a unique mode of action for killing many species of caterpillars, including the tomato, tobacco, and cotton bollworms, besides controlling the larvae and moths of corn earworms provided they get the Spinosad on the body. The Spinosad alters the role of GABA and nicotinic channels that speed up rapid muscle contraction in larvae that leads to paralysis and death occurs, ultimately. This product is OMRI listed and recommended for organic production worldwide.
Add 2 ounces of the product per gallon of water and apply to corn silks using a mist sprayer against earworms.
Chemical Control
FMC- Talstar Pro
Talstar- Professional is 7.9% Bifenthrin which is a systemic insecticide and has been in the grower's use against bollworms for the last two decades. That's why many pests and caterpillars have developed resistance against it. Talstar is good to check the preliminary two instars of corn earworm larvae But, possess certain residual effects. Bifenthrin residues can stay up to 90 days in the environment and the soil and are not permitted to spray on foliage of edible plants throughout the US.
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Talstar is a highly concentrated product, and only 5-6 ml is mixed per gallon of water for applying on non-edible plants. Otherwise, add 10 ml per gallon of water for soil drenching. Read the product label carefully and follow the listed instructions.
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authorities should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used lawfully, consistent with the product's label.
Check out our other guides on common garden bugs.