What's Eating Your Garden Asparagus?

Asparagus officinalis

Reviewed by Kiersten Rankel M.S.

Quick Answer

For garden asparagus, the most likely culprit by far is the asparagus beetle, which chews emerging spring spears and skeletonizes the summer fern. Aphids cluster on the fern foliage and can stunt next year's crowns. Japanese beetles skeletonize fern leaves in midsummer in much of the Midwest and East. Spider mites flare in hot dry summers and bronze the fern.

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What does the damage look like?

Tap the closest match to jump straight to the fix.

Chew marks on spears or fern

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Tiny green clusters on the fern

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Skeletonized lacy fern leaves

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Bronzed fern in hot dry weather

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Pests, ranked by impact

Small leaf weevil resting on a green leaf

Asparagus beetles

Damage

High

Removal

Moderate

What it looks like

Two species attack asparagus. The common asparagus beetle is 6 to 7 mm long, blue-black with cream rectangles edged in red along the wing covers. The spotted asparagus beetle is reddish-orange with 12 black spots. Both lay dark eggs upright on spear tips like tiny standing pegs. Larvae are gray-green slugs feeding on the summer fern.

What the damage looks like

Brown chew marks and curled tips on emerging spears in spring make harvest unsellable. Through summer, larvae and adults strip the needle-like fern foliage to bare stems. Defoliated fern can't photosynthesize and the crowns store less energy, which weakens next spring's spear crop.

How to get rid of them

Option 1

Hand-pick adults and larvae into soapy water

Walk the bed in the morning when beetles are sluggish, holding a jar of soapy water under each spear or fern frond.

Tap or knock beetles and larvae into the jar. They drop when disturbed, so the jar catches what flicks off.

Rub off any dark eggs standing upright on spear tips with a gloved thumb. Repeat every 2 to 3 days through the spear-cutting season and again on the summer fern.

Option 2

Cut and burn or bag the fern at season end

After the first hard frost browns the fern, cut every stalk to the soil line and bag or burn the debris off-site. Adults overwinter inside hollow fern stems and under bed litter, so removing the fern in fall removes most of next spring's beetles before they emerge.

Option 3

Keep the bed clear of weeds and old debris

Pull weeds and rake out dead spear stubs and leaf litter through the season. A clean bed gives adults nowhere to hide between feedings, which makes hand-picking more effective and slows the population through the year.

Option 4

Spinosad spray as a last resort during heavy pressure

Mix spinosad (Captain Jack's Deadbug Brew or Monterey Garden Insect Spray, ~$12 to $15) per the label.

Spray spears or fern at dusk, coating both sides of the foliage. Spinosad breaks down in sunlight.

Wait the label-stated harvest interval before cutting spears. Repeat after 7 days only if hand-picking and bed cleanup haven't held the population back.

Aphids

Damage

Medium

Removal

Easy

What it looks like

The asparagus aphid is a powdery blue-green insect 1 to 2 mm long. Clusters densely along the soft fern foliage and on the growing tips of summer ferns. Often arrives in midsummer and builds fast in warm weather. A specialist on asparagus, so you won't see it on neighboring crops.

What the damage looks like

Bushy, stunted fern tops with shortened branches and a tufted look at the growing tips. Fern foliage yellows around dense colonies. Heavy aphid feeding through the summer reduces how much energy the crowns store, so next spring's spear crop comes in thinner and shorter.

How to get rid of them

Option 1

Strong water blast every 2 to 3 days for 2 weeks

Hold a hose nozzle 12 inches from the affected fern tops and spray at high pressure. Most aphids dislodge and don't make it back to the plant. The fastest, cheapest fix and works without chemicals. Repeat every 2 to 3 days for 2 weeks until the colonies stop rebuilding.

Option 2

Insecticidal soap on fern tips, every 5 days for 3 rounds

Use ready-to-use insecticidal soap (Safer Insect Killing Soap, ~$10).

Spray the fern tips and any clusters along the branches at dusk, coating both sides of the foliage.

Repeat every 5 days for 3 rounds. That covers the egg-to-adult cycle in warm weather.

Option 3

Plant alyssum or yarrow along the bed edge

Sow sweet alyssum or plant yarrow within 3 feet of the asparagus bed in spring. Both attract ladybugs and lacewings, which feed on aphids through the summer. Established plantings keep aphid pressure low without sprays and come back year after year.

Metallic green and copper Japanese beetle (Popillia japonica) on a lantana flower

Japanese beetles

Damage

Medium

Removal

Moderate

What it looks like

Adults are 1 cm long with shiny copper wing covers and a metallic green head. Feed in clumps of 5 to 30 on the fern, often in full sun on the upper part of the plant. Active from late June through August across most of the eastern and central US. Not a problem west of the Rockies.

What the damage looks like

Lacy skeletonized fern, where beetles eat the tissue between the fine needle branches and leave the veins behind. Heavy clumps brown the upper fern within a few days. Fern damage in summer means weaker crowns and a thinner spring spear crop the following year.

How to get rid of them

Option 1

Hand-pick into soapy water at dawn

Walk the bed early in the morning when beetles are cold and sluggish, holding a jar of soapy water under each clump.

Tap the fern. Beetles drop straight into the jar.

Repeat daily through the 6 to 8 week feeding window. Daily picking through July is the single most effective home control.

Option 2

Skip the pheromone traps near the bed

Pheromone traps catch beetles but also attract more from nearby yards than they kill. If you use a trap, place it at least 50 feet from the asparagus bed. Most home gardens are better off without one.

Option 3

Apply milky spore to the lawn for long-term control

Milky spore (Bonide Milky Spore, ~$30) is a soil-applied bacterium that infects Japanese beetle grubs in the lawn before they emerge as adults. Apply once to the lawn around the bed in late summer. Takes 2 to 3 years to build up but suppresses the local population for a decade.

Spider mites

Damage

Medium

Removal

Moderate

What it looks like

Almost invisible without a hand lens. Yellow-green to red-orange specks running along the underside of fern needles. Hot, dry, dusty summers trigger a population boom, especially in beds along driveways or south-facing fences where airflow is poor and the bed dries out fast.

What the damage looks like

A dusty bronze cast spreading across the upper fern in midsummer. Fine webbing strung between the fine fern branches in heavy infestations. Bronzed fern photosynthesizes poorly. A summer-long mite outbreak weakens the crowns and trims next year's spear crop.

How to get rid of them

Option 1

Shower the fern weekly for 3 weeks

Spray cool water on the underside of the fern with a hose nozzle for 30 to 60 seconds per plant. Mites can't reattach quickly when knocked off, and the rinse humidity slows the survivors. Repeat weekly for 3 weeks. The fastest fix during a summer outbreak.

Option 2

Mulch the bed and keep it watered through summer

Mulch 2 to 3 inches deep with straw or wood chips after the spear-cutting season ends. Water deeply once a week through summer dry spells. Drought stress is what triggers spider mite outbreaks on asparagus, and a steadily moist bed keeps populations low.

Option 3

Neem oil at dusk, every 5 days for 3 rounds

Mix 2 tablespoons cold-pressed neem oil and 1 teaspoon dish soap per gallon of water.

Spray the underside of the fern and along the stems at dusk. Neem breaks down in sunlight.

Repeat every 5 days for 3 rounds. Covers the full egg-to-adult cycle in summer heat.

Stay ahead of all of them

Four habits that keep an asparagus bed productive across its 15 to 25 year life.

Walk the spear bed every morning in cutting season

Asparagus beetles lay eggs on spear tips that you'll cut and bring to the kitchen anyway. A 30-second walk and any eggs you spot get rubbed off or cut with the spear. Daily cutting season inspection is the single best beetle control.

Cut and remove the fern at the first hard frost

Asparagus beetles overwinter inside hollow fern stems and under bed litter. Cutting the fern to the soil line in fall and bagging or burning the debris removes most of next spring's beetles before they ever emerge.

Mulch the bed 2 to 3 inches deep after cutting season

Mulch keeps the soil moist through summer dry spells, which heads off the drought stress that triggers spider mite outbreaks. It also smothers weed seedlings, which gives beetles fewer hiding spots between the spears.

Plant alyssum and yarrow along the bed edge

Both plants flower through summer and pull in ladybugs, lacewings, and parasitic wasps that feed on aphids and beetle larvae. Established companion plantings keep pest pressure low without sprays and come back every year alongside the crowns.

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About This Article

Kiersten Rankel M.S.

Botanical Data Lead at Greg · Plant Scientist

About the Author

Kiersten Rankel holds an M.S. in Ecology & Evolutionary Biology from Tulane University. A certified Louisiana Master Naturalist, she has over a decade of experience in science communication, with research spanning corals, cypress trees, marsh grasses, and more. At Greg, she curates species data and verifies care recommendations against botanical research.

See Kiersten Rankel's full background on LinkedIn.

Editorial Process

Pest identification and treatment guidance verified against Asparagus officinalis field reports from Greg's botanical database, cross-referenced with university extension sources and published horticultural research.

127+ Greg users growing this plant

USDA hardiness zones 3a–8b

Citations:
NC State Extension
Aphid photo: Scot Nelson (CC0)
Spider mite photo: Clemson University - USDA Cooperative Extension, Bugwood.org (CC BY 3.0 US)
Beetle placeholder: Prasan Shrestha (CC BY-SA 4.0)
Japanese beetle photo: Kmtnewsman0 (CC BY-SA 4.0)