Daylily Pests: Deer, Slugs, Thrips, Aphids & More

What Is Eating My Daylilies? Deer, Slugs, Thrips, Aphids and Other Pests

You walk into the garden expecting another round of daylily flowers and discover that half the buds have disappeared. Or perhaps the leaves are full of ragged holes, the flowers are opening scarred and distorted, or healthy-looking foliage has suddenly developed hundreds of tiny pale speckles.

Something may be attacking your daylilies – but identifying the culprit takes more than finding the nearest insect.

Daylilies (Hemerocallis) are generally tough, dependable perennials, and many pest encounters remain minor. Deer, slugs and snails, thrips, aphids, spider mites, daylily gall midge, daylily leafminer, cutworms, beetles, grasshoppers, and other animals can all damage daylilies, but they leave very different clues.

The fastest route to the right diagnosis is therefore not to ask, “What pests live in my garden?” Start with what part of the daylily was damaged and what the damage actually looks like.

A missing flower bud points in a different direction from a swollen bud that never opens. Ragged holes suggest something very different from pale stippling. Sticky scapes, winding trails inside leaves, shredded foliage, and scarred petals each narrow the possibilities further.

1Start With the Damage: Daylily Pest Diagnosis at a Glance

The American Daylily Society emphasizes that different pests injure plants in different ways. Some chew away tissue. Others pierce cells and suck plant juices. Some feed inside buds, while leafminers tunnel between the surfaces of a leaf.

That makes the damage pattern one of the most useful identification tools you have.

This table narrows the suspects, but it does not replace inspection. Before treating anything, find evidence that the suspected pest is actually responsible.

2Deer: When Daylily Buds and Flowers Disappear

If healthy daylily buds seem to vanish overnight, deer should be high on your list of suspects.

Daylilies should not be treated as reliably deer-resistant. Deer may browse foliage, flower scapes, buds, and flowers, and a favorite clump can lose much of its display just before the buds were ready to open.

Because deer lack upper incisors, browsed vegetation is often torn or ragged rather than neatly clipped. Look beyond the damaged daylily for hoofprints, droppings, browsing on nearby plants, and repeated damage at a height deer can easily reach.

How to Protect Daylilies From Deer

• Exclude deer where pressure is severe: Fencing, netting, or temporary barriers around particularly valuable plants are the most dependable way to prevent browsing.
• Use repellents strategically: Repellents can reduce browsing, but effectiveness varies with deer pressure, weather, product, and local feeding behavior. Follow label directions and reapply when required.
• Protect high-value buds and flowers: Temporary barriers can be especially useful during the weeks when flower scapes and buds are developing.
• Adjust the surrounding planting: Where browsing is a recurring problem, combine vulnerable favorites with plants deer are less likely to eat. Gardenia’s Deer-Resistant Plants Guide can help you choose shrubs, perennials, grasses, bulbs, and other plants for deer-prone gardens.

3Slugs and Snails: Ragged Holes and Night Feeding

Irregular holes and shredded leaf margins are classic chewing symptoms, and slugs and snails are common suspects on tender daylily growth.

These molluscs are most active at night or during cool, damp conditions. During the day they shelter beneath boards, stones, pots, dense vegetation, plant debris, or other places that remain moist.

A shiny slime trail is particularly useful evidence.

Damage may be most conspicuous on young leaves, where feeding can leave the foliage looking shredded between the veins.

How to Control Slugs and Snails

• Remove hiding places: Clear boards, dense weeds, excess debris, and other damp refuges immediately around susceptible plants.
• Inspect after dark: Handpicking can work surprisingly well in a small garden because slugs and snails are most active at night.
• Use shelter traps: Boards or similar objects can be placed deliberately as daytime hiding places, then checked and cleared regularly.
• Use bait only when needed: Choose a product specifically labeled for slug and snail control and follow the label carefully. Iron phosphate baits are among the lower-risk options commonly used in integrated pest management programs.
• Skip the salt: Salt can damage plants and increase soil salinity, so it is not an appropriate garden treatment.

4Thrips: Scarred Buds, Streaked Leaves and Distorted Flowers

Thrips tabaci (Onion Thrips) feeding on plant tissue

Thrips are frustrating because they are tiny and often feed in protected areas between leaves, inside buds, and among flower parts.

Several species can occur on daylilies, including the daylily thrips, Frankliniella hemerocallis.

On leaves, feeding can create pale patches or streaks. Tiny dark droppings may appear near the injured tissue. Bud feeding can produce streaking, distorted flowers, damaged petals, or bud drop, while flower scapes may develop corky lesions.

Do not diagnose thrips from one unattractive flower. Heat, weather injury, physical damage, and other pests can also spoil daylily blooms.

Look for a repeated pattern across several buds, leaves, flowers, or scapes and inspect protected areas closely.

How to Manage Thrips on Daylilies

• Confirm the diagnosis first: Look for a recurring pattern of pale streaking, bud or flower distortion, corky scape lesions, and tiny dark droppings before treating.
• Avoid drought stress: Keep plants adequately watered, particularly during dry weather, because thrips problems tend to increase in dry conditions.
• Avoid excessive nitrogen: Heavily fertilized plants with lush tender growth can experience greater thrips problems.
• Protect beneficial insects: Encourage natural enemies and avoid unnecessary broad-spectrum pesticide use.
• Remember the limits of contact sprays: Insecticidal soap may reduce exposed thrips, but insects hidden inside buds and tightly protected foliage can be difficult to reach.
• Escalate only when damage justifies it: If additional treatment is needed, use products labeled for the intended ornamental plant and pest and follow current local Extension recommendations, since registrations and timing vary by region.

5Aphids: Sticky Growth and Colonies Hidden in the Fans

Aphids are small, soft-bodied insects that pierce plant tissue and feed on sap. The daylily aphid, Myzus hemerocallis, is particularly associated with Hemerocallis.

Look deep between the leaves as well as along tender growth. Daylily aphids can feed in colonies tucked into the fans, where they are easy to overlook.

Two clues are especially helpful.

The first is honeydew, the sticky substance aphids excrete while feeding. The second is the presence of tiny whitish cast skins left behind as the insects molt.

Heavy infestations can distort tender growth, but a few aphids do not automatically require treatment. Lady beetles, lacewings, syrphid fly larvae, parasitic wasps, and other natural enemies can keep populations below damaging levels.

How to Control Aphids on Daylilies

• Dislodge exposed aphids: A firm stream of water can remove many insects. Inspect the plant again before deciding whether another treatment is necessary.
• Check deep inside the fans: Daylily aphids often shelter between the leaves, where they can be difficult to see and difficult to reach.
• Protect natural enemies: Lady beetles, lacewings, syrphid fly larvae, parasitic wasps, and other predators can help keep populations below damaging levels.
• Avoid excessive nitrogen: Aphids are especially attracted to lush, tender growth produced by heavy fertilization.
• Use contact treatments only when justified: Insecticidal soap may help where aphids can be hit directly and the product is labeled for the intended use, but hidden aphids may escape treatment.
• Avoid unnecessary broad-spectrum pesticides: Eliminating aphid predators can turn a temporary population increase into a more persistent problem.

6Spider Mites: Fine Stippling in Hot, Dry Weather

Spider mite webbing on a pepper leaf

Spider mites do not chew holes in daylily leaves. They pierce individual plant cells and remove their contents.

The result is often fine pale or yellow stippling scattered across the foliage. As infestations become heavier, leaves can look faded, bronzed, dry, or generally unhealthy.

This damage is easily confused with drought or heat stress because spider mite problems themselves often increase during hot, dry weather.

Inspect both sides of affected leaves. The mites are extremely small and may require magnification to see clearly. Fine webbing can develop when populations become heavier, although webbing is not always obvious early in an infestation.

How to Reduce Spider Mites

• Confirm stippling before treating: Inspect both sides of affected leaves and look for mites, eggs, or fine webbing rather than assuming heat or drought alone caused the damage.
• Reduce drought stress: Keep daylilies adequately watered because spider mites are favored by hot, dry conditions.
• Use water as a physical control: A firm spray directed particularly toward leaf undersides can help dislodge mites.
• Protect predators: Beneficial predatory mites and insects help suppress spider mite populations.
• Use soaps or oils only when needed: Insecticidal soaps or horticultural oils may be useful when labeled for the plant and pest, but thorough coverage is essential and label precautions matter, especially during heat or drought stress.
• Be cautious with broad-spectrum insecticides: Some insecticide use can worsen mite outbreaks by disrupting the natural enemies that help keep mites in check.

7Daylily Gall Midge: Swollen Buds That Never Open

Daylily gall midge, Contarinia quinquenotata, produces one of the most distinctive daylily pest symptoms.

Affected flower buds become shorter, wider, and abnormally swollen instead of developing the normal elongated shape. They fail to open and may eventually dry or rot.

Inside an affected bud, numerous tiny, pale larvae can be found feeding in watery plant tissue.

This is not a pest every gardener will encounter. Geography matters. RHS reports daylily gall midge as widespread in England and Wales and established in parts of Scotland, while the American Daylily Society notes that the pest was first identified in North America in 2001.

What to Do About Daylily Gall Midge

• Confirm the symptom: Look for unusually short, wide, swollen buds that fail to open, rather than assuming every damaged bud is caused by gall midge.
• Remove affected buds promptly: Pick off and destroy galled buds rather than dropping them around the plant. This removes larvae before they leave the bud and enter the soil.
• Use bloom timing where the pest is persistent: RHS notes that cultivars flowering after the main gall-midge activity period are less likely to be affected.
• Keep geography in mind: Confirm that daylily gall midge occurs in your region before making the diagnosis.

8Daylily Leafminer: Winding White Trails Inside Leaves

If a leaf develops long, pale, winding trails that appear trapped inside the blade rather than sitting on its surface, investigate daylily leafminer.

The daylily leafminer, Ophiomyia kwansonis, is a small fly whose larvae feed between the upper and lower surfaces of daylily leaves.

The feeding trail creates distinctive whitish serpentine mines that widen as the larva grows.

This pattern differs from leaf streak, rust, slug feeding, and mite stippling. The tissue has been mined internally rather than simply spotted, scraped, or chewed away.

Inspect new daylilies before introducing them into an established collection. If leafminer is confirmed, remove and destroy mined leaves where practical rather than leaving infested foliage in the bed.

Because distribution can change, gardeners encountering an unfamiliar leafminer should consult local Extension or other regional plant-health guidance for current information.

9Cutworms, Beetles, Grasshoppers and Other Chewing Pests

Not every chewed daylily is the work of a slug or deer.

The American Daylily Society records a wider range of occasional pests, including cutworms, Japanese beetles, cucumber beetles, tarnished plant bugs, grasshoppers, leafhoppers, white grubs, and others.

Most will not be equally important in every region or garden.

Cutworms

Cutworms are caterpillars that typically feed at night and hide near or just beneath the soil surface during the day. Depending on the species, they can damage tender growth near the base or climb plants to feed.

If young shoots have been chewed close to soil level, inspect nearby soil and debris for curled caterpillars.

Japanese Beetles and Other Beetles

Adult beetles may chew flowers or foliage when locally abundant. Identify the beetle before deciding how to manage it. An irregular hole alone does not tell you which chewing insect caused it.

Grasshoppers

Grasshoppers can remove substantial pieces of leaf or flower tissue during outbreak years. Their larger bites are very different from the pinprick stippling created by spider mites or the internal mines produced by leafminers.

White Grubs

Some scarab beetle larvae live below ground and have been reported feeding on daylily roots. Suspect root-feeding grubs only when the plant is declining and grubs are actually found around affected roots.

Do not diagnose an underground pest simply because a daylily is weak. Poor drainage, root or crown problems, planting stress, drought, and disease can produce similar above-ground symptoms.

10Do Not Confuse Pest Damage With Daylily Disease

One of the easiest ways to waste time – and pesticides – is to treat a disease or growing problem as though something were eating the plant.

Daylily leaf streak can produce brown lesions surrounded by yellow tissue. Daylily rust produces orange-yellow pustules. Crown and root problems may cause yellowing, wilting, loose fans, or collapse.

Those symptoms require a very different response from deer browsing or slug feeding.

Use the pattern:

• Missing tissue points toward chewing or browsing.
• Fine stippling suggests tiny piercing feeders such as spider mites.
• Sticky honeydew strongly supports an aphid investigation.
• Scarred, streaked, or malformed buds and flowers can indicate thrips.
• Short, swollen unopened buds suggest gall midge where it occurs.
• Winding trails contained inside the leaf suggest leafminer.
• Defined lesions, pustules, soft crowns, or collapsing fans should move disease and root problems higher on the list.

For a broader symptom-by-symptom diagnosis, use Gardenia’s Daylily Problems: Yellow Leaves, Spots and Poor Bloom.

11When Should You Actually Treat a Daylily Pest?

Finding a pest does not automatically mean you need to eliminate it.

The American Daylily Society advises assessing the amount of injury before taking control measures. A few insects may cause little meaningful damage, and natural enemies may reduce the population without intervention.

Before treating, ask:

• Is this pest actually responsible for the damage?
• Is the injury cosmetic, or is flowering or plant vigor being significantly affected?
• Is the population increasing?
• Are beneficial predators already present?
• Can infested material simply be removed?
• Would handpicking, water sprays, habitat cleanup, barriers, or another physical control solve the problem?

If treatment becomes necessary, choose the least disruptive effective option available. If a pesticide is required, select a product labeled for both the pest and the intended ornamental use and follow the label exactly.

Broad-spectrum treatments can eliminate beneficial insects along with pests and may sometimes allow secondary pest populations to increase.

12Reduce Daylily Pest Problems Before They Become Serious

Healthy daylilies are not pest-proof, but sensible garden care reduces stress and makes plants better able to tolerate minor feeding.

Keep Plants Adequately Watered

Severe drought stress can reduce plant vigor and favor pests such as spider mites. Moisture is particularly important while scapes and buds are developing and during flowering.

Avoid Excessive Nitrogen

More fertilizer does not automatically mean healthier plants. High nitrogen levels can produce lush, tender growth that is attractive to several pests, including aphids.

For complete soil, feeding, watering, and maintenance guidance, use Gardenia’s complete daylily planting and care guide.

Use Targeted Cleanup

Different pests call for different kinds of sanitation. Remove unnecessary damp hiding places around beds where slugs and snails are a recurring problem. Destroy mined leaves when daylily leafminer is confirmed. Remove galled flower buds promptly where daylily gall midge occurs.

Inspect New Daylilies

Look carefully at new plants before adding them to an established collection. Check leaves for mines and stippling, inspect the fans for aphids, examine buds for unusual swelling or scarring, and look at the crown and roots for signs of poor health.

Protect Beneficial Insects

Lady beetles, lacewings, syrphid fly larvae, parasitic wasps, predatory mites, spiders, and other predators contribute to natural pest control.

A diverse garden with flowering plants and restrained pesticide use gives those beneficial organisms a better chance to work.

13Healthy Leaves but Damaged Buds? Narrow the Search

If the foliage looks healthy but flowers are failing, concentrate first on buds, scapes, browsing, and recent growing conditions rather than treating the whole plant for a foliage disease.

If the plant is healthy but simply produces few scapes or flowers, the culprit may not be a pest at all. Sunlight, planting depth, crowding, moisture, excessive feeding, recent division, and cultivar behavior can all affect flowering.

Gardenia’s Why Are My Daylilies Not Blooming? Causes and Fixes provides a separate diagnostic path for those plants.

14Build a Garden That Is Easier to Diagnose and Manage

Pest management becomes easier when a garden is designed around plants suited to the site rather than forcing stressed plants to survive unsuitable conditions.

Use Gardenia’s Plant Finder to explore plants by sunlight, soil, moisture, size, tolerance, wildlife value, and other characteristics.

If you are choosing among daylily cultivars, use the Daylily Comparison Tool to compare plants side by side.

You can then use Gardenia’s Garden Design Tool to combine plants, compare mature dimensions and seasons of interest, and build a planting palette suited to your garden.

Good plant selection will not eliminate every aphid, slug, deer visit, or thrips outbreak. But matching plants to their growing conditions reduces avoidable stress and makes unusual damage easier to recognize.

The Bottom Line: Identify the Damage Before You Fight the Pest

Daylilies can attract deer, slugs and snails, aphids, thrips, spider mites, gall midge, leafminers, and other occasional pests, but most gardens will never experience all of them.

The useful skill is not memorizing a long pest list. It is learning how to read the plant.

• Missing buds should make you investigate browsing.
• Ragged holes plus slime point toward slugs or snails.
• Sticky growth and white cast skins support an aphid diagnosis.
• Scarred or distorted buds and flowers may indicate thrips.
• Fine pale stippling, particularly in hot dry weather, raises suspicion of spider mites.
• Short, swollen buds that refuse to open are characteristic of daylily gall midge where the pest occurs.
• Winding white trails inside leaves point toward daylily leafminer.

Then confirm the suspect before treating.

Finding an insect does not prove it caused the damage. Finding damage does not automatically mean a pesticide is necessary. And a disappointing daylily does not necessarily have a pest problem at all.

The most reliable diagnosis combines affected plant part + damage pattern + timing + confirming evidence.

Once those clues agree, the right response becomes much clearer.

Frequently Asked Questions

References

American Daylily Society – Daylily Pests – specialist guidance on pest identification from feeding damage, deciding whether control is necessary, beneficial insects, and lower-impact management.

American Daylily Society – Aphids – guidance on daylily aphids, honeydew, cast skins, nitrogen, natural enemies, and the limitations of contact treatments.

American Daylily Society – Thrips – guidance on thrips identification, leaf and flower symptoms, drought, nitrogen, and management.

American Daylily Society – Spider Mites – guidance on spider mite symptoms, hot and dry conditions, webbing, and management.

Royal Horticultural Society – Hemerocallis Gall Midge – identification, distribution, biology, affected buds, and management of daylily gall midge.

UC Statewide IPM – Snails and Slugs – identification, habitat management, handpicking, barriers, and slug and snail bait guidance.

Gardenia – Daylily Problems: Yellow Leaves, Spots and Poor Bloom – Gardenia’s symptom-based guide to distinguishing pests, diseases, water stress, crown problems, and normal foliage decline.

Gardenia – Why Are My Daylilies Not Blooming? – Gardenia’s diagnostic guide to sunlight, planting depth, moisture, crowding, plant health, pests, and other causes of poor flowering.

Gardenia – How to Grow and Care for Daylilies – complete planting, watering, feeding, maintenance, pest, disease, and flowering guidance.

Updated: August 2026 • Reviewed by Gardenia Editors