Corn earworms are a destructive pest that’s extremely common in the garden.
They love the warmer winters. These insects are the larvae of armyworm moths. They’re extremely hard to see once they burrow into the crop.
While infested crops need to be thrown out, there are some things you can do to save the remaining ones.
There are some simple DIY remedies you can practice to help reduce the population of earworms.
In this guide, you’ll learn about:
Why earworms are in your garden
Natural ways to get rid of them
Preventing corn earworm infestations
If you have questions about your infestation, you can post them at the end of this page. I’ll try to get back to you ASAP (as usual).
Let’s learn about how to control, manage, and get rid of corn earworms.
Sections
What’s a corn earworm?
Corn earworms, also known as H. zea or Boddies, are caterpillars that can grow up to 2 inches in length.
They can be brown, orange, red, green, or even yellow. They’re marked with stripes that go down their back and are masters of camouflage. They can even be maroon or pink. Some are almost black.
As you can tell by their name, they’re a common garden insect that feeds on corn. This is why their colors match that of corn kernels so they can feast while in hiding.
They’re similar to their cousins the tobacco budworm, so many pest management techniques can be used between the two species.
They’re commonly confused with the fall armyworm, corn borer, bean cutworm, and tobacco budworm, so it’s important that you distinguish between the species so you know what insect you’re darling with.
The larvae feed on foliage but will feed on the nutritious tips of corn ears, beans, or tomatoes. They usually infest the crop from the tip, rather than the sides like the European corn borer.
What do they turn into?
The corn earworm is simply the larval form of the adult earworm moth. The adults are brown with patterned wings.
The earworms do what you need to worry about as they do the majority of the damage to your crop.
The moth doesn’t do significant harm, so don’t waste your time on them. The moths are about 1” in length from wing to wing. The front wings have a comma-shaped spot.
How to tell the difference between these caterpillars
The body of the corn earworm is covered by bumps that have black hairs coming out. The heads are also tan or dark brown.
Compared to tobacco budworms, you can distinguish them by checking out the shape of the mandible and the presence of micro spines.
Only the budworm has spikes on the bumps of the body with black hairs. The sorghum webworm is also a common insect that may be found with earworms.
Identification
These bugs are easy to identify if you know what to focus on. There are several species, but the most common are H. zea, H. armigera, H. assulta, H. punctigera, and other subspecies in the Helicoverpa genus.
For adults, look for the “comma” markings on the wings.
For larvae, look for caterpillars that have stripes going down the back. Segments are visible with a darker, tan head.
The worm looks very similar to a cutworm or budworm. See this video for more info:
Lifecycle
Corn earworms possess a similar lifecycle to any other caterpillar. The adult moths will look a place to oviposit their eggs in the springtime after they mate.
Eggs
Hornworm eggs are small, yellow, and deposited individually. They lay eggs in fresh corn silk.
Each egg is about the size of half a pinhead with no pattern in laying. The larvae will begin following the silk channel to the corn ear tip where they’ll eat the kernels.
Once they get inside the ear, the cone is destroyed. The eggs are tiny white and laid singly in the foliage on the corn silk. Eggs will get a brown ring on the top when they’re about to hatch, which takes about 2-5 days. Eggs are deposited in a row.
This is where they start seeking a host plant to infest.
Larvae
The larvae will hatch from the eggs. They’re green with black heads and tiny caterpillar hairs on the body. They’ll begin to feed on the corn ear tips. As they eat, they’ll burrow into the crop over time.
They get bigger until they reach about 1.5″ in length. Once they’re full size, they can be green, brown, or even pink.
Pupation
In the winter, the larvae are fully grown. They’ll drop to the soil line to pupate for the winter. If the temperature doesn’t dip below 25F, the larvae will turn into moths when temperatures warm up in the spring. Then they mate.
Signs of earworm damage
Corn earworms are voracious. They’re one of the most expensive and costly pests in the US.
For farms in areas where they can overwinter, they can do some real damage. The caterpillars will eat valuable crops and also stop plants from blooming as they feed on blossoms, buds, and fruit.
Earworms generally hide in grassy, woody, or agricultural farms.
On corn, the larvae will feed on the silks, which can stop pollination. When they get to the kernels, they’ll eat at the tip downward. This can also introduce pathogens into the ears. If the ears have not produced silk, the caterpillars will burrow into the ear.
While the larvae don’t generally move from one ear to another, they can cause extensive damage to a single ear. Larvae can also damage whorl corn by feeding on the leaves.
Caterpillars will burrow into fruits, feed for a short period, then continue on to other fruits if the fruit does not supply enough food.
Tomato is easily damaged by earworms when corn isn’t present or silking. Lettuce will be infested at the head.
These caterpillars will cause major damage to crops. This is why they’re such a nuisance in the garden, but a disaster in the farmlands.
Do they bite?
Yes, corn earworms do bite. Their bite can be very painful, so you don’t want to just dive in there with your bare hands.
They also produce toxins that can cause adverse reactions in humans and pets.
So always use PPE to protect yourself (gloves, jeans, closed-toed shoes, etc.) before venturing into the foliage that may contain corn earworms.
Never try to handle them directly. Consult an extent micro before you attempt any DIY pest control program on your own.
Did you know they like to bite so much that they even eat each other? Yes, they’re cannibals.
Once they get inside, it’s hard to see them. Sometimes you can see the adults foraging for nectar. Freshly silking corn is highly inhabitable for larvae to hide inside. The moths lay eggs on the silks of the corn. However, adult moths have been seen in the daytime foraging for food.
Did you know earworms have been seen to migrate over 400 miles? That’s crazy.
Both the larvae and the moths will hide during the day. Moths come out at dusk. When sampling for pests, scout in the early morning or early evening. This is the time to catch them while feeding.
What do they eat?
Younger caterpillars will eat their own eggshell for nutrients, then venture on to feed on younger, tender leaves. As they get older, they’ll move on to fruit. Corn earworms don’t only eat corn.
They love to munch on a variety of foods, such as:
Beans, corn, cotton, peanuts, sorghum, tomato, and ornamental (bedding and flowering).
Caterpillars will produce silk threads as they eat, so if you see a bunch of silk in a small area, it’s likely a feeding site for them.
You’ll also find their poop under their feeding sites, which look like small black pebbles.
They have chewing mouthparts so they can eat larger, stiffer foliage.
Adult moths have siphoning mouths to suck up juices for the plants.
What else do they eat?
This list is lengthy, but if you really want to know everything they’ve been spotted eating…
Corn earworms also eat artichoke, asparagus, cabbage, cantaloupe, collard, cowpea, cucumber, eggplant, lettuce, lima bean, melon, okra, pea, pepper, potato, pumpkin, snap bean, spinach, squash, sweet potato, and watermelon alfalfa, clover, cotton, flax, oat, millet, rice, sorghum, soybean, sugarcane, sunflower, tobacco, vetch, wheat, common mallow, crown vetch, fall panicum, hemp, horsenettle, lambs quarters, lupine, morning glory, pigweed, prickly sida, purslane, ragweed, Spanish needles, sunflower, toadflax, and velvetleaf, have been reported to serve as larval bait, ripening avocado, grape, peaches, pear, plum, raspberry, strawberry, carnation, geranium, gladiolus, nasturtium, rose, snapdragon, milkweed, Joe Pye weed, and zinnia.
Corn earworms have been seen on over 200 types of plants.
But their preferred plants are sorghum and corn. As you can see, they have a wide variety of plants they can eat. This makes them an extremely adaptable nuisance.
Damaged crops should never be used as compost because they’re infected. They need to be properly disposed of using insecticides.
Where do they come from?
Corn earworms are found all throughout North America. They can be found in other countries as well, so they’re not limited to just our geography.
In the US, earworms don’t like the colder temperatures, so they shy away from the northern states. They’re commonly found in Kansas, Virginia, New Jersey, Ohio, Texas, etc.
If the state is warmer, they’re likely going to be able to infest it. The worm overwinters depending on the location and the weather. In the Pacific Northwest, the earworm can winterize as far as southern Washington!
How to get rid of corn earworms naturally
Corn earworm in all its glory.
This section covers some common ways to get rid of corn earworms at home without sprays or synthetics.
Note that some of these may not be applicable to your situation, so exercise common sense. Start with the easiest method then scale up if it works. If not, then try something else.
If you have any questions about your earworm situation, please leave your question at the end of this bug guide.
Sampling for corn earworms – Do you have an infestation?
You can sample the corn earner population if you’re not sure what kind of bug is eating your crops.
If you suspect that it’s earworms, there are a few ways you can catch them. Use a blacklight or pheromone trap. Both sexes will be drawn toward light traps, but only males will go to pheromone traps.
If you see more than 5 moths caught overnight, it’s generally a good signal that earthworms are present.
Manual removal
You can manually remove them using a pair of gloves with other PPE. These worms will bite and are toxic. Pick them off gently.
Then dunk them into a bucket of soapy water. This will kill them instantly. If you have a lot of them, use a sweep net or drop cloth to loosen them.
You can also shake the plant to get them off. Then let them fall onto a tarp or bucket of soapy water.
Make sure you use protective gloves and other gear. Corn earworms are poisonous and will emit a toxin that can harm humans and pets.
They can bite almost invisibly. NEVER handle corn armyworms if you don’t know what you’re doing or don’t have adequate equipment to protect yourself.
Consult a licensed professional exterminator before you attempt to manually remove them.
Blacklight traps
Adult earworms can be baited into black lights to kill them. This will stop their breeding cycle so you reduce the number of insects in the next progeny.
You can find black light lamps at hardware stores.
These are basically those zapper lights. They work because the adult moths will be drawn to the black light just like flies.
Prune infested crops
Homeowners can prevent most damage from earworms by removing the damaged parts. Cut the tips of damaged sweet corn ears.
This will completely eliminate the need for further action.
Utilize pheromones
Pheromones can be used to lure adult moths into traps that they can’t get out of.
You can find these moth traps at your local hardware store. They’re easy to use.
You just hang them near the infestation sites. The males will go in and then get stuck on some kind of adhesive. It’s that simple. Replace when necessary. Use as directed.
This is a passive way to get rid of the moths without needing to spend a lot of time or energy.
Commercial growers will use pheromone traps to monitor the presence of these moths.
Dispatch traps right before the first crop of corn begins to tassel. One trap is enough for a field, since moths will head in the direction of the prevailing winds.
This should be the southeast corner of the farm or garden.
Bacillus thuringiensis
Bt is a bacteria that can provide some relief to your crops. These nematodes are available commercially and you can easily apply them to your home garden.
They work by infesting the larvae as they land on the surface to pupate. The larvae will then be killed upon nematode infestation.
Of course, the caterpillar only drops after it’s done eating.
So the damage will be done. But it can stop them from pupating into the moths in the spring, which can instantly put a halt to their breeding.
Some of the newer Bt varieties differ in that they contain multiple genes for earworms, so they provide excellent levels of control.
Consider planting Bt varieties with multiple traits in later plantings since moth counts in the pheromone traps are often high later in the season.
Plant resistant varieties
Some varieties of corn have been created for warm resistance.
If you’re able to find them for sale, opt for these strains instead.
Row covers
Row covers can be excellent for protecting smaller crops from infestation.
You’ll need to find a cover that has a netting small enough so that moths and earworm caterpillars can’t get in.
The netting will let your crops receive sunlight, water, fertilizer, etc.
But they keep the bugs out. When you shop for one, make sure it’s the right size. And you’ll want to secure it well at the soil level so the bugs can’t get in.
Plant early
Some corn can be planted early because sweet corn that’s harvested before August will often have little damage.
Later planted corn will have major damage. Consider planting early varieties, a specialty in states prone to earworms like Indiana.
Trap cropping
This is an effective measure to get rid of these insects. The way it works is you plant other crops nearby that’ll bait the moths away.
Moths that are depositing eggs will seek out other crops like lima beans or tomatoes.
Weed-eating larvae will then migrate to crops. Try mowing the weeds first so they don’t have anywhere to hide.
In northern areas, you can plant or harvest early enough so that the moths don’t have time to deposit eggs.
But note that it’ll vary widely depending on the insect’s behavior and population density. They do the most damage late in the growing season.
Tilling the soil in the fall can reduce overwintering success in southern states.
Predators that eat corn earworms
Even though they do have some nice patterning and colors to camouflage themselves into the fruit, there are some that’ll gladly eat them up.
General predators will feed on their eggs and larvae, with over 100 identified species.
You should be able to utilize some of these predators to help control their population. The most accessible one is the ladybird beetle.
You can buy them online in bulk, then release them into the infested area over time.
Others include pirate bugs, green lacewings, damsel bugs, flower beetles, and birds. Some nematodes are also good at getting rid of them, such as S. riobravis or H. heliothidis.
Plant a surplus
You can plant more crops to offset the damaged crop if you need to meet a certain quota for harvest. Each season, you can estimate the amount of earworms that’ll infest your plants. Plant more to balance in out.
Corn earworms will eat flowers, foliage, or crops. So plant more if you rely on them!
Preventing corn earworms
If you’re growing host plants, corn earworms will infest them. You can help prevent corn earworms by doing the following:
Prune any damaged of infested fruit/veggies
Dispose of infested crop properly (don’t use it as compost!)
Use insecticides (pyrethroids, carbamates, or organophosphates)
Utilize natural enemies of corn earworms
Implement a pest management program
Use row covers or netting
Set up moth lamps or blacklights
Commercial solutions
There are many insecticides that are suitable for gardens.
But you must read and follow the label instructions. Always use as directed and read the hazards. Use organic insecticides when possible.
If you have people or pets that’ll be in the garden, you need to pay extra attention to what you use.
If you’re lost and don’t know what to buy, look for insecticides that have the following ingredients:
Carbaryl
Bifenthrin
Cyhalothrin
Esfenvalerate
Cyfluthrin
Spinosad
Look for the active ingredient and make sure it matches at least one of the ingredients. These will kill earworms effectively.
They may be sold under different trade names, but just check the ingredients.
Currently an active researcher in the pest control industry for the past 8 years- with a focus on using natural and organic methods to eliminate pest problems.
I share handy DIY pest techniques I come across here to help out others (and possibly save them from a mental breakdown).
