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Spinach and Beet Leafminers

Pegomya hyoscyami and P. betae[3]

Spinach and beet leafminers are small gray to brown flies whose white maggots feed between the upper and lower surfaces of spinach, chard, beet and related leaves, leaving blotchy mines that turn brown.[1][2]

Group
Insect
Order
Diptera
Family
Anthomyiidae
Sources
3 cited
Updated
2026-10-16
Brown blotch mine made by spinach leafminer larvae inside a leaf
Brown blotch mine made by spinach leafminer larvae inside a leaf. Photo: Braden J. Judson, public domain (CC0), via iNaturalist
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Adults are slender gray to black or brown flies about 1/4 to 1/3 inch long, with dark stripes on the thorax and clear wings.[1][2]
  • Larvae are whitish, cone-shaped maggots inside the leaf; eggs are white and laid in groups of four to eight under the leaves.[1]
  • Mines are irregular blotches, opaque at first and later brown.[1]

Look-alikes

Look-alikeHow to tell them apart
Other leafminersMany flies and moths mine leaves; these attack the beet and spinach family.[1][2]

Where it lives

Seen in Maryland and Minnesota gardens and high tunnels.[1][2]

Biology and life cycle

They overwinter as pupae in the soil; flies emerge in April and May to lay eggs, with a second generation in June.[1][2]

Larvae mine the leaves, then drop to the soil to pupate.[1]

Damage and signs

  • Hosts are beets, chard, spinach and weeds such as lamb's-quarters, chickweed and pigweed; the spinach leafminer may also feed on peppers.[1][2]
  • Feeding barely affects root crops but can ruin spinach and chard grown for their leaves.[1][2]

Health risk

None to people or pets.[1][2]

Control

Prevention

Rotate plantings away from last season's spot, because pupae stay in that soil, and cover new plantings with row covers.[1]

Sanitation

Remove and destroy the first infested leaves and leaves with eggs, and control weed hosts.[1]

Pesticides

For spinach, labeled insecticides include spinetoram, dinotefuran and thiamethoxam; options are more limited for other crops.[1]

Common questions

What are the brown blotches inside my spinach and chard leaves?
Often spinach or beet leafminer mines.[1][2]
Are the beets still safe to eat?
Root crops are barely affected; mined leaves are the problem.[1][2]
How do I prevent them?
Remove early infested leaves, rotate, control weeds and use row covers.[1]

Sources

  1. University of Maryland Extension, “Beet and Spinach Leafminers (updated October 23, 2024).” extension.umd.edu/resource/beet-and-spinach-leafminers (accessed 2026-10-16)
  2. University of Minnesota Extension, “Spinach leafminer (What insect is this? diagnostic pages).” apps.extension.umn.edu/garden/diagnose/insect/garden/flies/small/spinachleafminer.html (accessed 2026-10-16)
  3. iNaturalist, “Pegomya hyoscyami taxon page (order and family).” www.inaturalist.org/taxa/1524674 (accessed 2026-10-06)

Updated 2026-10-16. Built from sourced records. Spot an error? Tell us.