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To identify what is eating your sweetcorn, first note where the damage is: before emergence, on seedlings or stalks, at the ear tip, or through the side of the husk. Then look for larvae, frass, holes, beetles, grubs, tunnels, and wildlife activity; damaged kernels alone are not enough to identify the culprit.
Ear-tip chewing often points to corn earworm, while a hole in the side of the husk with feeding around the middle of the ear makes fall armyworm or European corn borer worth checking. Missing seed, stunted seedlings, and damage below ground suggest different causes, including birds or wireworms.
Sweetcorn damage diagnosis at a glance
| What you see | Likely cause | What to check |
|---|---|---|
| Kernels chewed mainly at the ear tip | Corn earworm | Look for a caterpillar and frass near the tip. Larvae enter through the silks; their color can vary. |
| A hole through the side of the husk and feeding around the middle of the ear | Fall armyworm or European corn borer | Inspect the entry hole, ear, leaves, and stalk for larvae, frass, and other feeding signs. |
| Chewed or hollowed individual kernels; small beetles or pale grubs | Sap beetles | Look for small oval beetles and tiny pale grubs. They may exploit injury from other ear pests, but can also attack directly when populations are high. |
| Stalk holes, brown frass, shot-holes in leaves, or lodging | European corn borer | Check stalk and leaf damage and look for larvae in tunnels. Larvae are pale and regularly spotted. |
| Seed missing before emergence | Birds or other seed predators | Look for disturbed seed and observe the seedbed. Birds seen feeding support this diagnosis, but missing seed alone does not prove it. |
| Poor emergence, wilted or stunted seedlings, dark or purple color, or holes and tunnels in seed, roots, or lower stems | Wireworms | Gently inspect below ground for tunnels or feeding injury. Former sod, pasture, alfalfa, and grassy weeds are risk clues, not proof. |
| Mature ears damaged or missing overnight | Raccoons are one possibility | Observe when damage occurs and look for wildlife evidence; overnight damage alone does not identify a species. |
| Empty kernels at the tip without chewing or other feeding evidence | Incomplete pollination or growing stress | Do not assume an animal or insect ate the missing kernels; inspect the ear and growing conditions. |
Inspect the ear and plant
- Locate the injury. Note whether it is at the tip, along the side of the ear, in the stalk or leaves, or below ground.
- Peel back the husk. Look for an entry hole, frass, a caterpillar, beetles, grubs, and the location of chewed or hollowed kernels.
- Check leaves and stalks. If the ear is damaged alongside holes, frass, or lodging, inspect for stalk-boring larvae and leaf injury.
- Inspect seedlings carefully. For missing or stunted plants, check the seed, roots, and lower stem for tunnels or holes.
- Observe suspected wildlife. Note whether seed disappears before emergence or mature ears are attacked, and use exclusion that matches the suspected animal.
More than one pest can damage an ear, and some pests take advantage of injury caused by another pest. Pennsylvania Extension describes earworm as typically entering through the silks and feeding near the tip, while fall armyworm or European corn borer may enter through the husk. These patterns are useful clues, not a substitute for inspecting the plant.
Recognizing common ear pests
Corn earworm
Corn earworm larvae commonly feed on kernels near the ear tip and enter through the silks. Look for a caterpillar and frass in the damaged area. Mature larvae may vary in color, from pale green to pink or nearly black, and can have prominent stripes. Color alone is not a reliable identification.
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Fall armyworm and European corn borer
A hole through the side of the husk with feeding around the middle of the ear makes fall armyworm or European corn borer possibilities to investigate. European corn borer may also cause small holes in stalks, brown frass, shot-holes in leaves, and lodging. Its larvae are pale or pinkish gray with dark spots; Penn State Extension notes that they generally lack the prominent stripes seen in earworm or fall armyworm.
Feeding can let mold enter damaged ears, so inspect the injury rather than relying on the entry hole alone. Pest prevalence and management recommendations from Pennsylvania sources may not apply in other regions.
Sap beetles
Chewed or hollowed individual kernels together with small oval beetles and tiny pale grubs can indicate sap beetles. They may feed from silking through ear maturity. Penn State Extension describes them as often exploiting damage from primary ear pests, but notes that they can attack ears directly when surrounding populations are high.
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Seedling and below-ground damage
Birds and missing seed
Birds may remove corn seed before seedlings emerge. The University of Minnesota Extension suggests leaving floating row cover over the seedbed until emergence to discourage bird predation. A row cover is a targeted measure for seed predation; it does not address insects feeding inside ears.
Wireworms
Wireworms feed below ground and can injure or kill seed before emergence. After emergence, look for wilted or stunted plants, dark or purple coloration, and holes or tunnels in seeds, roots, or lower stems. Cool spring conditions can worsen injury by slowing plant development. A history of sod, pasture, alfalfa, or grassy weeds may raise suspicion, but does not confirm wireworms.
What to do next
- Record the damage location and pattern. Photograph the whole plant and the ear before removing damaged tissue.
- Look for confirming evidence. Check for larvae, frass, holes, beetles, grubs, and tunnels; inspect stalks and leaves if they are also damaged.
- Match any barrier to the problem. Floating row cover may discourage birds from taking seed before emergence. An electric fence is a possible deterrent for raccoons at mature ears, not a treatment for insect damage.
- For suspected wildlife, observe activity and use suitable exclusion. If the evidence is uncertain, do not assume that one animal is responsible based only on the timing or amount of damage.
- Use local advice for control decisions. Consult your local Extension service and follow the pesticide label if a pesticide is appropriate.
The University of Minnesota Extension sweetcorn guide discusses row cover for seed predation, raccoon damage, and trimming caterpillar-damaged ears. Its recommendations reflect Extension guidance and should be considered alongside local conditions.
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Can you eat damaged sweetcorn?
The University of Minnesota Extension advises cutting off the affected portion of an ear with ordinary caterpillar damage and cooking the remaining portion if it is sound. Do not apply that advice to corn that is moldy, spoiled, or otherwise questionable; discard ears with those conditions.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.FAQ
What eats kernels at the tip of a sweetcorn ear?
Corn earworm is a leading possibility when kernels are chewed near the tip. Look for a caterpillar and frass, and remember that an empty tip without chewing may have a different cause.
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What causes a hole in the side of a corn husk?
A side-entry hole with feeding around the middle of the ear makes fall armyworm or European corn borer worth checking. Inspect the ear, leaves, and stalk for larvae, frass, and additional feeding signs.
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What are the small beetles and grubs in my corn?
Small oval beetles and tiny pale grubs alongside hollowed or chewed kernels can indicate sap beetles. They may exploit earlier pest injury, though high populations can also attack directly.
Why are my corn seedlings missing or stunted?
Birds may remove seed before emergence. Wireworms can damage seed, roots, and lower stems below ground, causing poor emergence, wilt, or stunting. Inspect the seed and plant below the soil before deciding which is responsible.
Can I cover corn seed to stop birds?
The University of Minnesota Extension suggests floating row cover over the seedbed until emergence as a way to discourage birds from taking seed. It is not a general solution for ear pests or wildlife feeding on mature corn.
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Can I eat corn after a caterpillar has damaged it?
The University of Minnesota Extension advises cutting off the affected part and cooking the remaining portion when the rest of the ear is sound. Do not use this as a safety assurance for moldy, spoiled, or questionable corn.
The Bottom Line
Start with where the damage is, then look for evidence that confirms the culprit. Ear-tip chewing suggests corn earworm; a side hole and mid-ear feeding suggest other caterpillars; hollowed kernels with beetles or grubs point to sap beetles; and tunnels below ground can indicate wireworms. Match any protection to the diagnosed problem and use local Extension guidance for control decisions.
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