Affected Plants: Flowering bulbs, including true bulbs, corms, tubers, and rhizomes.
Primary Insect Pests: Aphids, thrips, bulb flies, iris borer, and lesser canna leafroller.
Related Pests: Bulb mites, slugs, and snails. Bulb mites are related to spiders; slugs and snails are not insects.
Primary Damage Symptoms: Distorted leaves or flowers; silvery or brown leaf speckles; damaged, soft, or rotting bulbs and rhizomes; and rolled or chewed leaves.
Most Important Prevention Strategy: Inspect bulbs before planting and remove infested or dead plant material as described in the pest sections.
Biological Controls: Ladybird beetles, lacewings, syrphid flies, damsel bugs, and parasitic wasps help control aphids; lacewings and ladybird beetles also feed on thrips.
Chemical Control: Use pesticides only when needed and follow the pest-specific guidance and product label directions. For aphids, begin with a strong stream of water or, when appropriate, insecticidal soap.
The most common pests of flowering bulbs, in general, are aphids, bulb mites, slugs, and snails. In addition, thrips, bulb flies, borers, and leafrollers are among other pests that can also cause problems for certain flowering bulbs. While slugs and snails are not insects, they are major pests of flowering bulbs. For more information on these pests and their control, see Snails & Slugs in the Home Garden (HGIC 2357).
NOTE: As used in this fact sheet, the term “bulb” refers to true bulbs, as well as plants that have bulb-like structures, such as corms, tubers, and rhizomes.
Aphids on Flowering Bulbs
Aphids are small, sap-feeding insects that can distort new growth and flowers on flowering bulbs.
Identification
Aphids are small, soft-bodied, pear-shaped insects with piercing-sucking mouthparts. Depending on the species, they may be yellow, green, pink, or black. Adult aphids may be winged or wingless. Aphids usually gather in clusters on new growth and become a pest problem during cool spring weather through to the summer.
Damage and Symptoms
- Feeding can cause deformed leaves and flowers.
- Aphids excrete sticky honeydew. Sooty mold fungi can grow on it, leaving dark splotches on the plant surfaces.
Prevention and Treatment
Monitoring
Check new growth for clusters of aphids and look for sticky leaves or dark sooty mold.
Cultural Controls
Remove aphids with a strong stream of water applied regularly.
Biological Control
Ladybird beetles (ladybugs), lacewings, syrphid flies, damsel bugs, and parasitic wasps feed on or parasitize aphids, generally keeping them under control.
Chemical Control
Aphids multiply rapidly, and insecticides can also kill their natural enemies, often worsening the problem.
When predator population numbers are low, insecticidal soap can be effective; thoroughly spray both leaf surfaces.
For severe infestations, products containing:
- Bifenthrin
- Cyfluthrin
- Lambda cyhalothrin
- Zeta cypermethrin
- Permethrin
See Table 1 for product examples. Follow the label directions and precautions.
Bulb Mites on Flowering Bulbs
Bulb mites (Rhizoglyphus species) are not insects but are more closely related to spiders and feed on bulbs.
Identification
Adult bulb mites are tiny, yellowish-white, somewhat transparent, and slow-moving.
Damage and Symptoms
- Feeding weakens plants and can cause stunted, off-color leaves and deformed flowers.
- Infested bulbs often develop soft, dying areas and fail to grow.
Prevention and Treatment
Monitoring
Look for signs of mite damage or soft areas.
Cultural Controls
- Most importantly, when purchasing new bulbs, check for signs of mite damage or buy only hot-water-treated bulbs.
- Dipping cured bulbs in 120 °F water for 2 minutes can kill mites.
- Discard heavily infested bulbs. Handle bulbs carefully, as even slight injuries create entry points for bulb mites.
- When possible, do not replant bulbs in infested soil.
Thrips on Flowering Bulbs
Thrips are slender, sap-feeding insects that can damage leaves and flower buds on flowering bulbs.
Identification
Several thrips species attack flowering bulbs, including:
- Gladiolus thrips (Taeniothrips simplex)
- Onion thrips (Thrips tabaci)
- Flower thrips (Frankliniella tritici)
Adults are slender, tan to dark brown, about 1/20 to 1/16 inch long, and have fringed wings. They often hide in protected areas of the plant. Nymphs resemble adults but are smaller.
Damage and Symptoms
- Adults and nymphs scrape surface cells and suck plant sap.
- Flower buds fed on may die without opening.
- Light feeding can cause brown or silvery speckles or streaks on leaves.
- Severe infestations can stunt and distort leaves and flowers, which may turn brown and die.
Prevention and Treatment
Monitoring
Watch for speckling, streaking, distorted growth, or flower buds that fail to open. Bright blue or yellow sticky traps can help protect plants by catching adults.
Cultural Controls
To make a simple trap:
- Paint a cardboard or wooden board bright blue or yellow.
- Coat it with petroleum jelly.
- Attach it to stakes.
- Place it near the flowering bulbs.
Commercial sticky-coating products, including Tanglefoot Tangle-Trap Sticky Coating and Arbico Organics Sticky Stuff Sticky Coating, can be brushed onto painted cards.
Biological Control
Green lacewings and ladybird beetles feed on thrips. Avoid unnecessary insecticide use to conserve these beneficial insects.
Chemical Control
Insecticidal soap may be used, but thorough coverage is required. When needed for very valuable plants, apply spinosad or acephate as soon as damage appears. Confirm that the plant species is listed on the product label. See Table 1 for examples, and follow all label directions and precautions.
Lesser Bulb Flies on Flowering Bulbs
Lesser bulb fly larvae tunnel through bulbs, causing decay and poor growth the following year.
Identification
Adult lesser bulb flies (Eumerus species) are 3/16 to 3/8 inch long, dark blue, and have a metallic bronze sheen. Their larvae (maggots) are 1/16 to 3/8 inch long and white to grayish-yellow.
Larvae survive winter inside bulbs, then move into the soil in spring to pupate. Adults emerge, mate, and females lay eggs on or near bulbs, in openings left by dying leaves, on the soil surface, or on leaves at the bulb neck.
Damage and Symptoms
Larvae enter and then tunnel through the bulb. The bulbs begin to decay and fill with a semi-liquid material, die, or produce only very small leaves the following year.
Prevention and Treatment
Monitoring
When digging bulbs for division, check for soft or damaged bulbs and destroy infested ones.
Cultural Controls
- Remove and trim leaves as soon as they dry in the spring.
- Lightly till the soil after removing leaves to destroy soil openings that adult females use to reach bulbs and lay eggs.
- Handle bulbs carefully and discard soft bulbs.
- For slightly damaged bulbs, hot-water treatment at 109.4°F to 111.2°F for 3 hours can control these pests. Monitor the water temperature closely and do not exceed the stated range, because higher temperatures can damage bulbs.
Narcissus Bulb Flies on Daffodils
Narcissus bulb fly larvae tunnel into daffodil bulbs and feed on the soft tissue.
Identification
Adult narcissus bulb flies (Merodon equestris) resemble small bumble bees with yellow or orange-brown bands. The plump larvae (maggots) are grayish-white to yellow, ranging from 1/16 inch long when newly hatched to ¾ inch when mature.
Damage and Symptoms
Females lay eggs on the leaves near the soil surface or crowns. After hatching, larvae tunnel into bulbs and feed on the soft tissue.
Infested bulbs may be hollowed out, soft, spongy, and prone to rot. Some survive but produce small, weak leaves the following year. Larvae overwinter in bulbs and move into the soil in the spring to complete their life cycle.
Prevention and Treatment
Monitoring
When digging daffodils for division, inspect bulbs and discard any showing signs of infestation.
Cultural Controls
- Remove leaves as soon as they dry in the spring.
- Lightly till the soil after leaf removal to destroy openings that adult females use to locate bulbs for egg-laying.
- Floating row covers can help prevent egg-laying.
- Keep daffodils healthy with a shallow layer of mulch and fall fertilization.
- When dividing bulbs, attempt to kill the larva by stabbing it with a needle or wire inserted through the entry hole. However, there is always a chance of missing the maggot and damaging the bulb even more.
Hot-water treatment at 109.4°F to 111.2°F for 40 minutes is effective. Do not let the water exceed 111.2 °F; higher temperatures can damage the bulb.
Iris Borers on Iris
Iris borer is a caterpillar and the most serious pest of iris.
Identification
Iris borer (Macronoctua onusta) larvae can reach 1 3/8 inches long. The mature caterpillar is pale yellowish-pink to pink with a brown head and has rows of black spots along its sides. Adult moths emerge late in summer, mate, and lay eggs on old iris leaves and nearby plants. The eggs overwinter, and tiny caterpillars hatch in the spring.
Damage and Symptoms
Young caterpillars feed on new leaves. Leaf margins may appear water-soaked, ooze plant sap, and become ragged.
Caterpillars tunnel inside leaves, then move down to the rhizomes and feed on or inside them. One iris borer can consume a rhizome before moving to another.
Bacterial and fungal root rot often develops in damaged rhizomes. At maturity, the borer leaves the rhizome and enters the soil to pupate. Damage may first be noticed when rhizomes are dug for transplanting in late summer.
Prevention and Treatment
Monitoring
If borer damage has occurred, hold young leaves up to the sun in spring; caterpillars inside are readily visible.
Cultural Controls
- Remove old stems and leaves in the fall or winter to eliminate overwintering eggs.
- Crush small caterpillars between thumb and finger or with a pointed stick.
- When dividing rhizomes, cut off and destroy heavily infested ones. For minimally damaged rhizomes, you can try to kill the larva by inserting a needle or wire through its entry hole. You may miss the larva and further damage the rhizome.
Chemical Control
If iris borer has been a problem in the past, spray rhizomes in spring when the new foliage is 4 to 6 inches tall, then again 2 weeks later.
Insecticides that control the iris borer include:
- Acephate
- Bifenthrin
- Cyfluthrin
- Lambda cyhalothrin
- Permethrin
- Zeta cypermethrin
See Table 1 for examples. Follow all label directions and precautions.
Lesser Canna Leafrollers on Cannas
Lesser canna leafroller caterpillars feed inside leaves and roll or fasten leaf edges together.
Identification
The lesser canna leafroller (Geshna cannalis) is the caterpillar of the moth. Newly hatched caterpillars are about 1/16 inch and cream colored. Mature caterpillars reach 7/8 inch; their bodies become greenish, while their heads remain yellowish.
Caterpillars overwinter in rolled, dead canna leaves and mature into adults in spring. Females lay eggs on canna, and mature caterpillars spin a cocoon before becoming adults. More than one generation occurs each year.
Damage and Symptoms
Newly hatched caterpillars tunnel between the upper and lower leaf surfaces. As they become too large, they exit onto the upper leaf surface and fasten leaf edges together or roll one edge of an already open leaf.
They generally feed on the leaf’s upper surface but may bore through rolled leaves.
Infested leaves may:
- Have several holes through them
- Fail to open
- Prevent plants from blooming
Prevention and Treatment
Monitoring
Look for leaf edges fastened or rolled together, holes, and leaves that fail to open.
Cultural Controls
Remove and destroy above-ground canna plant parts in winter to reduce caterpillar overwintering in rolled, dead canna leaves.
Chemical Control
The natural insecticide Bacillus thuringiensis (Bt) can control leafrollers when applied three times at weekly intervals starting when damage is first noticed. Apply Bt in the evening; if leaves are already rolled, spray into them.
For severe infestations, one or two sprays of a foliar-systemic insecticide, such as acephate or spinosad, may kill the borers inside the leaves.
See Table 1 for examples of brands and products.
Control of Flowering Bulb Insect Pests (Table 1)
The products below are examples associated with active ingredients discussed in this factsheet. Formulations and labels vary. Use only a product labeled for the target plant and pest, and follow all label directions and precautions.
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 |
| Bacillus thuringiensis
(Bt) |
Bonide Thuricide Bacillus thuringiensis (Bt)
Garden Safe Brand Bt Worm & Caterpillar Killer Monterey Bt Natural Guard by Fertilome Caterpillar Killer Spray with Bt Natural Guard by Fertilome Caterpillar Killer Spray with Bt Ready to Use Safer Brand Caterpillar Killer For Trees, Shrubs, & Vegetables Concentrate II Southern Ag Thuricide Bt Caterpillar Control Ferti-lome Dipel Dust Biological Insecticide SA-50 Southern Ag Dipel Dust |
| 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 Insecticide 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-Spray BioAdvanced Science-Based Solutions Rose & Flower Insect Killer Ready-to-Use |
| 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 II Whitney Farms Insecticidal Soap 1 |
| 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 |
| 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 |
| Zeta Cypermethrin | Gordon’s Bug-No-More Lawn & Garden Insect Control
Gordon’s Bug-No-More Large Property Insect Control GardenTech Sevin Insect Killer Concentrate GardenTech Sevin Insect Killer Ready-to-Spray |
- RTS = Ready to Spray (hose-end applicator)
- RTU = Ready to Use (pre-mixed spray bottle)
- Do not apply insecticidal soap when temperatures are above 90 °F or to drought-stressed plants.
- Spray insecticides late in the day.
- Follow product-label restrictions, including any directions for protecting pollinators.
Pesticide disclaimer: This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named.
Recommendations are for South Carolina conditions and may not apply elsewhere. Use pesticides only according to label directions. Pesticide recommendations are for South Carolina and were legal at the time of publication, but registration and use patterns may change under state and federal regulation.
Follow all directions, precautions, and restrictions listed on the label.
Pesticides are updated annually. The last updates were made on 10/26 by N. Jordan Franklin.
Originally published 11/99
