Do all chewing insects feed at night?

No. Slugs, snails, and earwigs are primarily nocturnal, feeding under cover of darkness and hiding in cool, moist spots like under mulch, boards, or pots during the day, which is why a flashlight check after dark is the best way to catch them in the act. Beetles such as Japanese beetles, caterpillars, and grasshoppers, on the other hand, are usually active and visible feeding during daylight hours, so you can often spot them directly on the plant. Matching your scouting time to the suspected pest, rather than only checking once during the day, makes it much easier to positively identify what's actually causing the damage.

Why do some plants get chewed more than others in the same garden?

Chewing pests are often drawn to particular plant families or even specific cultivars, so a garden can have heavy damage on one type of plant and almost none on its neighbor. Japanese beetles, for example, strongly prefer roses, grapes, and linden trees over many other ornamentals, while flea beetles favor young seedlings in the cabbage and eggplant families. Stressed or younger plants with more tender tissue are also generally more attractive and vulnerable to chewing insects than mature, vigorous plants, which is one more reason healthy cultural care indirectly reduces pest damage even though it isn't the direct cause.

Is it worth spraying an insecticide as a precaution before I see damage?

Generally no. Broad-spectrum preventive spraying on a schedule, before you've identified an actual pest, kills beneficial insects like predatory beetles and parasitic wasps that would otherwise help control the chewing pests naturally, and it can encourage resistance over time. Extension guidance consistently favors monitoring first, then targeting an identified pest with the least-disruptive effective option, whether that's hand-picking, a physical barrier, or a specific product used according to the label. Save spraying for a confirmed, ongoing problem rather than a routine precaution.

Can chewed leaves recover, or is the damage permanent?

The holes themselves don't heal or fill back in; once tissue is eaten, that damage on that particular leaf is permanent. However, a healthy plant that stops the underlying pest problem will usually grow new, undamaged foliage, and the older chewed leaves are simply replaced over the growing season as the plant continues to put out new growth. Cosmetic damage on a handful of leaves rarely threatens an otherwise healthy plant's survival; the bigger concern is ongoing, heavy feeding that outpaces the plant's ability to replace lost leaf tissue.

Daniel Brady · NH-Licensed Pesticide Applicator · License #782664

What Bugs Eat Holes in Leaves?

Usually a pest — chewing insects

The usual hole-makers are beetles, caterpillars, slugs, flea beetles, earwigs, and grasshoppers, and each one leaves a signature bite you can identify.

At a glance

The verdict: Usually a pest — chewing insects
Who fixes it: You
Category: Leaf-Symptom Diagnosis (pest vs disease vs care)

The short answer

Holes chewed into leaves are almost always the work of a chewing pest, not a disease or a care mistake. Japanese and other beetles skeletonize leaves between the veins, caterpillars and loopers leave larger ragged holes, slugs and snails leave ragged holes plus a slime trail worst after rain and at night, flea beetles punch tiny shot-holes, and earwigs and grasshoppers chew irregular or jagged margins. The pattern of the damage, plus whether you find frass, slime, or the insect itself, points to the culprit. True disease-caused holes and random mechanical damage are far less common than a chewing insect, and they look different up close, so a quick inspection almost always settles it.

What's really going on

Pest, disease, or how you're caring for it?

Most leaf problems aren't pests at all. Here's the honest split — the most likely cause, the less likely ones, and how to tell them apart before you treat anything.

Symptom: distinct holes chewed into leaf tissue

Confidence: high

PestMost likelythe usual cause
Ragged, skeletonized, or clean-punched holes with a pattern you can match to a specific chewer, often with frass, slime, or the insect itself nearby.
Japanese and other beetles (skeletonizing, lacy leaves)Caterpillars and loopers (ragged, larger holes)Slugs and snails (ragged holes plus slime trails, worst at night)Flea beetles (tiny round shot-holes)Earwigs and grasshoppers (irregular or jagged edges)
The tell:Match the damage signature to the culprit and look for frass, slime trails, or the insect itself on the leaf or nearby soil.
Diseasea less common cause
A hole with a discolored or dead-tissue ring around it, where infected tissue died and later fell out, leaving a shot-hole effect that can look like insect feeding at a glance.
Bacterial or fungal shot-hole diseaseAnthracnose lesions that drop out
The tell:Look for a ringed or discolored margin around the hole; true pest feeding leaves a clean or ragged edge without a disease lesion.
Care / environmenta rare cause
Random, irregular tears or punctures with no biological pattern, scattered without regard to leaf structure.
Hail damageWind-driven abrasion against another plant or structureMechanical tearing from handling
The tell:No frass, no slime, no consistent bite pattern, and it correlates with a specific weather event or physical contact rather than ongoing feeding.

How to tell them apart

Scout at the right time of day: slugs and earwigs feed at night, so check with a flashlight and look for slime trails and daytime hiding spots under mulch or pots, while beetles and grasshoppers are usually visible feeding in daylight. Pair that with the hole's shape: skeletonized tissue between veins points to beetles, larger ragged chunks point to caterpillars, and tiny round punctures point to flea beetles.

More than one chewing pest is often active in the same garden at once, so don't stop looking once you've confirmed one culprit if damage keeps spreading.

The honest router

Who actually fixes this?

YouGarden centerUNH ExtensionCertified arboristPest-control pro

Start here

You

Chewing damage in a garden bed starts with monitoring and simple hand controls, checking at night for slugs, scouting by day for beetles, and hand-picking or using barriers before reaching for any product.

Garden center — Hand-picking and barriers aren't keeping up and you want a targeted product such as an iron-phosphate slug bait, row cover, or insecticidal soap for soft-bodied stages.
UNH Extension — You can't identify the culprit from the damage pattern and want confirmation before treating.

Straight talk from Anchor

This isn't a pest-control-company job. Chewing insects on garden and landscape leaves fall outside the structural and yard pests Anchor treats, so we'd point you to a garden center or UNH Cooperative Extension rather than send a technician.

The full answer

The details, straight

Reading the hole to find the bug

The single most useful diagnostic is the shape and pattern of the damage. Skeletonized leaves, where the green tissue between veins is eaten away but the veins remain like lace, point to Japanese beetles and similar leaf beetles. Larger, ragged holes chewed from the leaf margin or middle are typical of caterpillars and loopers. Tiny, numerous round holes scattered across a leaf, sometimes called shot-holes, are the classic sign of flea beetles. Ragged holes with ragged, torn edges and a dried slime trail nearby point to slugs and snails, which feed at night and rest in cool, damp hiding spots by day.

The evidence that confirms it

Beyond the hole shape, look for the physical evidence chewing insects leave behind. Frass, which looks like small dark pellets, often collects near caterpillar feeding sites. A dried, silvery slime trail visible in daylight confirms slug or snail activity from the night before, even if you never see the animal itself. Silk webbing at a feeding site is another caterpillar tell. If you find none of this and the holes have a discolored, ringed margin instead, you're more likely looking at a disease that killed tissue before it fell out, not an actively feeding insect.

Matching the fix to the culprit

Once you've identified the chewer, the fix is usually simple and doesn't require broad-spectrum spraying. Hand-picking beetles into soapy water in the early morning when they're sluggish, using iron-phosphate slug bait or beer traps for slugs, installing floating row cover to physically exclude flea beetles and caterpillars, and encouraging natural predators all work well for these visible chewing pests. Insecticidal soap or a targeted product can help with heavier infestations of soft-bodied larvae, but identify the pest first, since a product aimed at the wrong culprit wastes effort and can still cause leaf burn if misapplied.

The gist

Key takeaways

Chewing holes in leaves are almost always a pest problem, not disease or care error.
The hole's shape names the culprit: skeletonized = beetles, ragged and large = caterpillars, tiny and round = flea beetles, ragged with slime = slugs.
Frass, slime trails, and silk are the physical evidence that confirms an active pest rather than a disease shot-hole.
Time-of-day scouting matters: slugs and earwigs feed at night, beetles and grasshoppers by day.
This is a garden-center and hand-control job, not structural pest control.

Not sure which bug is doing this?

Matching the hole pattern, timing, and evidence to the right culprit is the fastest way to fix it without wasting a product on the wrong pest.

See the full pest-vs-disease-vs-care triage

Local to New Hampshire

A note for New Hampshire gardeners

New Hampshire context

Japanese beetles are typically active in southern New Hampshire from late June into July or August, feeding by day and often clustering in groups on roses, grapes, and other favorite plants, while slugs are worst during the cooler, damper stretches of spring and fall that are common in the region. UNH Cooperative Extension's Ask UNH Extension Infoline (1-877-EXT-GROW) is a free resource for confirming which chewing pest you're dealing with before you buy a product.

NH-licensed applicator #782664 (NHDAMF, RSA 430) · NEPMA member · family-owned since 2017.

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Garden Chewing Pests Are Garden Work — But Your Home Is Our Job

Bugs eating holes in your garden leaves are a garden-center and monitoring job, and we'll always say so rather than oversell a treatment you don't need. Where Anchor Pest Services genuinely helps is the pests around your home: rodents, ants, ticks, and moisture pests drawn to leaf litter and debris against the foundation. Family-owned since 2017, NH license #782664, serving Manchester, Nashua, Concord and nearby towns.

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ID before treatment — beetle, caterpillar, or slug all point to different fixes
NH-licensed applicators (#782664) for structural and yard pests, not garden defoliators
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Keep Exploring

What Bugs Eat Holes in Leaves?

Pest, disease, or how you're caring for it?

Who actually fixes this?

The details, straight

Reading the hole to find the bug

The evidence that confirms it

Matching the fix to the culprit

Key takeaways

Not sure which bug is doing this?

A note for New Hampshire gardeners

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Garden Chewing Pests Are Garden Work — But Your Home Is Our Job

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