Daylily Diseases and Insect Pests in South Carolina

Quick Guide / At a Glance

Affected Plants: Daylilies (Hemerocallis species).
Primary Disease Types: Daylily leaf streak (Aureobasidium microstictum), daylily rust (Puccinia hemerocallidis), root-knot nematode (Meloidogyne species), and soft rot (Pectobacterium carotovorum).
Primary Insect Pests: Flower thrips (Frankliniella tritici), two-spotted spider mites (Tetranychus urticae), aphids, and daylily leafminer (Ophiomyia kwansonis). Other pests include slugs and snails.
Primary Causes: Fungal pathogens, bacterial infection, root-knot nematodes, insects, mites, poor soil drainage, poor air circulation, overhead irrigation, improper fertilization, and planting stress.
Most Important Prevention Strategy: Use disease-free plants, provide well-drained soil and good air circulation, avoid overhead irrigation, plant daylilies at the proper depth, and remove dead or infected foliage.
Chemical Control: Depending on the pest or disease, controls discussed include thiophanate-methyl, myclobutanil, propiconazole, chlorothalonil, insecticidal soap, spinosad, tau-fluvalinate, bifenthrin, cyfluthrin, lambda-cyhalothrin, permethrin, acephate, imidacloprid, and iron phosphate bait. Always read and follow pesticide label directions and precautions.

Related HGIC Resources

• Daylily (HGIC 1163)
• Root-Knot Nematodes in the Vegetable Garden (HGIC 2216).
• Snails & Slugs in the Home Garden (HGIC 2357)

Diseases and insects are generally not serious problems in the home garden when good cultural practices are followed. Daylilies (Hemerocallis species) should be planted in the fall or spring because of the summer heat in South Carolina. They prefer well-drained soil with adequate organic matter and a mostly sunny site.

Have the soil tested to determine the appropriate fertilizer analysis, then apply a slow-release fertilizer in spring before daylilies begin to bloom. Planting daylilies too deeply will reduce flowering and cause plant decline. For more information on daylily culture, please see Daylily (HGIC 1163).

Daylily Diseases: Leaf Streak on Daylily

Daylily leaf streak is a fungal disease that causes yellow streaks, browning, and leaf decline on daylilies.

Cause

Daylily leaf streak is caused by the fungus Aureobasidium microstictum.

Symptoms

• Elongated yellow streaks along the leaf mid-vein.
• Browning or spots on infected leaves with yellow borders.
• Symptoms usually develop from the leaf tip downward.
• Leaves that may wither and die completely.

Prevention and Treatment

Cultural Controls

• Isolate infected daylilies from healthy plants.
• Purchase disease-free stock plants.
• Propagate only from healthy specimens.
• Avoid overhead irrigation.
• In the fall, remove dead foliage from around the base of the plants.
• Dispose of foliage clippings because the fungus can overwinter on senesced foliage and produce spores the following spring.

Resistant Varieties

• Betty Bennet
• Edna Spalding
• Ella Pettigrew
• Globe Trotter
• Nancy Hicks
• Pink Superior
• Ron Rousseau
• Sudie
• Tropical Tones
• Upper Room
• Winsome Lady

Chemical Control

Thiophanate-methyl or myclobutanil may be applied to slow disease development and to protect susceptible new growth from infection. Begin sprays as new growth appears, making 3 or 4 applications at 2-week intervals. See Table 1 for examples of products.

Daylily Diseases: Daylily Rust on Daylily

Daylily rust is a fungal disease that causes yellow to brown leaf streaks and orange pustules on daylily foliage.

Cause

Daylily rust is caused by the fungal pathogen Puccinia hemerocallidis.

Symptoms

• Yellow to brown streaks on the leaves.
• Numerous small yellow spots.
• Small orange pustules on the lower surface of leaves
• Yellowish-orange urediniospores that rub off onto white tissue.
• Spores that can spread by wind or through contact with infected plants.
• Rapid disease spread.

Prevention & Treatment:

Cultural Controls

• Inspect and purchase disease-free plants, especially by checking the lower leaf surfaces.
• Check for and plant resistant cultivars.
• Avoid overhead irrigation.
• In the fall, remove dead foliage from around the base of daylily plants and dispose of the clippings.

Chemical Control

Propiconazole, myclobutanil, or chlorothalonil may be applied to aid in the control of daylily rust. Spray at 2-week intervals as needed, and additionally spray after cutting back plants. Do not spray chlorothalonil during the blooming period. See Table 1 for examples of brands and products.

Daylily Diseases: Root-Knot Nematode on Daylily

Root-knot nematodes can cause loss of vigor and severe decline in daylilies.

Cause

Root-knot nematodes (Meloidogyne species) feed on daylily roots and inject toxins. They are most common in sandy, moist soils and are generally more problematic on former cropland converted to residential use.

Symptoms

• Loss of vigor and severe plant decline.
• Poor growth and stunting.
• Yellowing and wilting.
• Plant death.
• Symptoms that resemble moisture stress.
• Small bumps or nodules on roots where the nematodes feed.

Prevention & Treatment

Cultural Controls

• Choose plants that are not susceptible to the root-knot nematodes.
• If root-knot nematodes are suspected, submit an entire plant sample to the Clemson Plant and Pest Diagnostic Clinic through a county Clemson Extension office for verification.
• Submit entire plant samples rather than soil samples because root galling is evident on affected roots.
• Remove and dispose of infested plants.
• Do not add infested plants to the compost pile.

For more information, please see Root-Knot Nematodes in the Vegetable Garden (HGIC 2216).

Daylily Diseases: Soft Rot on Daylily

Soft rot is a bacterial disease that affects the base of daylily flowers and the rhizomes.

Cause

Soft rot is caused by Pectobacterium carotovorum, a common soil inhabitant. High temperatures, poor air circulation, poor soil drainage, and improper fertilization favor disease development.

Symptoms

• Bacterial rot at the base of daylily flowers.
• Rot in the rhizomes.
• A strong, disagreeable odor from the crown or base of the plant.

Prevention & Treatment:

Cultural Controls

• Improve drainage in heavy clay soils by adding organic matter, such as composted pine bark or compost.
• Improve air circulation by pruning back overhanging shrubs.
• Avoid planting susceptible daylily varieties where other plants have shown soft rot symptoms.
• Allow wounded plants to heal, or cork over, before planting.
• Do not over-fertilize or over-water plants.
• Avoid overhead irrigation.
• Discard all infected plant material.

Daylily Insect Pests: Flower Thrips on Daylily

Flower thrips and other thrips species can be serious pests of daylilies.

Cause

Flower Thrips (Frankliniella tritici) are slender, dark-colored insects with fringed wings. Adults and nymphs feed by scraping surface cells and sucking plant sap.

Symptoms

• Flower buds that may die without opening.
• Silvery speckles or streaks on leaves with light infestations.
• Stunted and distorted leaves and flowers with severe infestations.
• Leaves and flowers may turn brown and die.

Prevention and Treatment

Sampling

1. Hold a sheet of stiff white paper under leaves and flowers.
2. Strike the paper with the plant parts.
3. Gently tip the paper to remove any bits of trash.
4. Examine the paper in bright sunlight.
5. Use a 10x magnifying lens to help see these small, fast-moving pests.
6. Thrips that are present will move around on the paper.

Thrips adults are less than ¹/₁₆-inch long and are typically found on leaves and between flower petals.

Cultural Controls

• Avoid insecticides when possible to protect naturally occurring enemies that feed on thrips.
• Use blue sticky traps near daylilies.
• Paint cardboard or wooden boards blue, coat them with petroleum jelly, attach them to stakes, and place them near the daylilies.

Chemical Control

For serious damage, insecticidal soap or spinosad sprays are recommended.

• Spinosad is a foliar-systemic insecticide that can penetrate unopened flowers to provide good thrips control.
• Always spray in the evening to lessen the spray impact on pollinating insects.
• Read and follow all label directions and precautions.

Daylily Insect Pests: Two-Spotted Spider Mites on Daylily

Two-spotted spider mites and other mite species can damage daylilies, especially during hot, dry periods.

Cause

Two-spotted spider mites (Tetranychus urticae) are not insects; they are more closely related to spiders. They use piercing mouthparts to puncture plant tissue and suck plant sap.

Symptoms

• Yellowish speckles on daylily leaves and flowers.
• Fine webbing on leaves that protects eggs and young mites.
• Speckles that run together during heavy infestations.
• Bleached or dead leaves.
• Stunted growth.

Damage often goes unnoticed until it is more severe, partially due to the mite’s tiny size.

Prevention and Treatment

Sampling

1. Hold a sheet of stiff white paper under leaves and flowers.
2. Strike the paper with the plant parts.
3. Gently tip the paper to remove any bits of trash.
4. Examine the paper in bright sunlight.
5. Use a 10x magnifying lens to help see these tiny pests.

They are very small, less than ¹/₅₀-inch long.

Cultural Controls

Remove nearby weeds, such as chickweed, before spring growth because spider mites overwinter on weeds.

Chemical Control

Apply insecticidal soap early in the infestation. For more severe infestations, tau-fluvalinate or bifenthrin sprays will control spider mites. See Table 1 for examples of brands and products. As with all pesticides, read and follow all label directions and precautions.

Daylily Insect Pests: Aphids on Daylily

Aphids can damage daylilies, especially during cool spring weather.

Cause

Aphids are soft-bodied insects that range in color from yellow-green to almost black. They feed on leaves and flower buds by inserting their mouthparts and sucking plant sap.

Symptoms

• Deformed leaves.
• Small warty growths on flower buds.
• Honeydew, a sugary liquid waste produced by aphids.
• Dark fungal growth, or sooty mold, on the foliage.

Prevention and Treatment

Biological Control

• Allow naturally occurring enemies, including green lacewings and ladybird beetles, to reduce aphid populations.
• Avoid unnecessary insecticide applications because contact insecticides may kill beneficial predators.

Chemical Control

Insecticidal soap sprays are a less toxic option that can help reduce aphid populations.

For more severe infestations, bifenthrin, cyfluthrin, lambda cyhalothrin, or permethrin sprays may be used. See Table 1 for examples of brands and products.

Daylily Other Pests: Slugs and Snails on Daylily

Slugs and snails can damage daylilies, especially in early spring when they feed on tender young growth.

Cause

Slugs and snails feed at night and hide in moist areas during the day.

Symptoms

• Ragged notches along leaf edges.
• Holes in the middle of leaves.
• Shiny, slimy trails near affected plants.

Prevention and Treatment

Cultural Controls

Remove mulch and leaf litter near the base of daylilies to eliminate daytime hiding places.

Chemical Control

Apply environmentally safe snail and slug baits containing iron phosphate near the beds. For more information, see Snails & Slugs in the Home Garden (HGIC 2357).

Daylily Insect Pests: Daylily Leafminer on Daylily

The daylily leafminer creates visible mines in daylily foliage, which can render infested plants unmarketable.

Cause

The daylily leafminer (Ophiomyia kwansonis) is a small black fly introduced into the US around 2006 from Japan and Taiwan. Adults lay eggs on daylily foliage in the spring, and pale-yellow larvae feed within the leaves.

Symptoms

• Meandering whitish mines in the leaves.
• Mines that become wider as the larvae grow.
• Mines remain visible throughout the life of the leaf.
• Tan pupae about the size of a grain of rice overwinter near the base of leaves or plants.
• Damage that is primarily aesthetic and not extremely significant to plant health.

Daylily leaf showing winding, whitish leafminer tunnels across the green leaf surface.

Prevention and Treatment

Cultural Controls

• Promptly remove and dispose of infested foliage.
• Clean up and dispose of all dead foliage at the end of the season to reduce overwintering pupae.
• Continue removing dead foliage to help reduce the spread of foliar diseases, including daylily leaf streak and daylily rust.

Biological Control

Sprays used to control the leafminer may affect natural predators and parasites that help reduce leafminer numbers.

Chemical Control

Imidacloprid sprays or plant drenches, acephate sprays, or spinosad sprays may be used to control daylily leafminer. Apply spinosad as soon as symptoms of mining are noticed. Spray late in the evening to reduce the impact on pollinating insects.

Acephate is a foliar systemic insecticide, meaning it will penetrate the foliage to kill the larvae within the leaves.

Fungicides for Disease Control on Daylilies (Table 1)

Active Ingredient	Example Product Names
Chlorothalonil	Bonide Fung-onil Multi-purpose Fungicide Concentrate Bonide Fung-onil Multi-purpose Fungicide Ready to Use Ferti-lome Broad Spectrum Landscape & Garden Fungicide GardenTech Daconil Fungicide Concentrate GardenTech Daconil Fungicide Ready-to-Us Hi-Yield Vegetable, Flower, Fruit And Ornamental Fungicide Ortho MAX Garden Disease Control Concentrate Southern Ag Liquid Ornamental and Vegetable Flowable Fungicide Tiger Brand Daconil
Mancozeb	Bonide Mancozeb Flowable with Zinc Concentrate Southern Ag Dithane M-45
Myclobutanil	Ferti-lome F-Stop Lawn & Garden Fungicide Monterey Fungi-Max Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate For Gardens
Propiconazole	Banner Maxx II Fungicide Bonide Infuse Systemic Disease ControlBonide Infuse Systemic Disease Control Lawn & Landscape Ready to SpFerti-lome Liquid Systemic Fungicide IIQuali-Pro Propiconazole 14.3 Fungicide
Thiophanate Methyl	Southern Ag Thiomyl Systemic Fungicide

Insecticides and Mite Controls for Daylilies (Table 1)

Active Ingredient	Example Product Names
Acephate	BioAdvanced Science-Based Solutions 2-in-1 Systemic Rose & Flower Care Granules with 6-9-6 Fertilizer Bonide Systemic Insect Control II
Bifenthrin	Hi-Yield Bug Blaster Bifenthrin 2.4 Ready to Spray Hi-Yield Bug Blaster II Bifenthrin 2.4 Ready to Spray Monterey Mite & Insect Control Monterey Mosquito Control Martin’s FLEE Ready to Use Yard Spray Ortho Outdoor Insect Killer Concentrate Ortho Bug B Gon Insect Killer for Lawns & Gardens1 Ortho BugClear Insect Killer for Lawns & Landscapes Bifen I/T Talstar P Professional Insecticide Up-Star Gold Insecticids Hi-Yield Vegetable & Ornamental Insect Control Granules Bonide Eight Insect Control Flower & Vegetable Above & Below Soil Insect Granules
Cyfluthrin	BioAdvanced Science-Based Solutions 24 Hour Lawn Insect Killer Ready-to-Spray BioAdvanced Science-Based Solutions Complete Brand Insect Killer for Soil & Turf Ready-to-Spray I BioAdvanced Science-Based Solutions Insect Killer for Lawns Ready-to-SprayBioAdvanced Science-Based Solutions Rose & Flower Insect Killer Ready-to-Use
Lambda Cyhalothrin	Bonide Eight Insect Control Garden & Home II Ready to Use Cutter Backyard Bug Control Spray Concentrate Cyzmic CS Controlled Release Insecticide Martin’s Cyonara Lawn & Garden Insect Control Martin’s Cyonara Lawn & Garden Insect Control Ready-to-Spray Spectracide Triazicide Insect Killer for Lawns & Landscapes
Horticultural Oil	Bonide All Seasons Horticulture Spray Oil Ready-to-Use Bonide All Seasons Horticulture & Dormant Spray Oil Ready-to-Spray Ferti-lome Horticultural Oil Spray Monterey Horticultural Oil Concentrate Monterey Horticultural Oil RTU Safer Brand Horticultural & Dormant Spray Oil Concentrate Southern Ag Parafine Horticultural Oil Summit Year-Round Spray Oil
Insecticidal Soap	Bonide Insecticidal Soap Multi-purpose Insect Control Ready to Use Garden Safe Brand Insecticidal Soap Insect Killer Miracle-Gro Nature’s Care Insecticidal Soap Natria Insecticidal Soap Ready-to-Use Natural Guard by ferti-lome Insecticidal Soap Concentrate Safer Brand Insect Killing Soap Concentrate I Whitney Farms Insecticidal Soap 1
Permethrin	Bonide Eight Insect Control Vegetable, Fruit, & Flower Concentrate Bonide Eight Yard & Garden Ready to Spray Hi-Yield 38 Plus Turf, Termite & Ornamental Insect Control Hi-Yield Lawn Garden Pet & Farm Insect Control Southern Ag Permetrol Lawn & Garden Insecticide Tiger Brand Super 10 Brand
Spinosad	Bonide Captain Jack’s Deadbug Brew Concentrate Bonide Captain Jack’s Deadbug Brew Ready to Spray Bonide Captain Jack’s Deadbug Brew Ready to Use Bonide Colorado Potato Beetle Beater Concentrate Conserve SC Turf & Ornamental Monterey Garden Insect Spray Monterey Garden Insect Spray RTU Natural Guard by ferti-lome Spinosad Bagworm, Tent Caterpillar & Chewing Insect Control Natural Guard by ferti-lome Spinosad Soap Ortho Insect Killer Tree & Shrub Concentrate Southern Ag Conserve Naturalyte Insect Control
Tau-Fluvalinate	BioAdvanced Science-Based Solutions All-in-One Rose and Flower Spray BioAdvanced Science-Based Solutions 3-in-1 Insect, Disease & Mite Control BioAdvanced Science-Based Solutions 3-in-1 Insect, Disease & Mite Control Ready-To-Use BioAdvanced Science-Based Solutions 3-in-1 Insect, Disease & Mite Control I

RTS = Ready to Spray (a hose-end sprayer)
RTU = Ready to Use (a pre-mixed spray bottle)
Pesticide products and labels can change. Always read and follow the current product label directions and precautions, and use only products labeled for the intended use.

Pesticides are updated annually. The last updates were made on 9/26 by N. Jordan Franklin.

Originally published 01/01