Pest profile

Carrot Rust Fly

Chamaepsila rosae (formerly Psila rosae) · Diptera: Psilidae[3]

The carrot rust fly is a small black fly whose maggots tunnel through the lower third of carrot roots, leaving rust-colored burrows and scarred, rot-prone carrots.[1][2]

No licensed photo of this species is available yet; the identification notes below describe what to look for.

How to identify it

  • Adults are small, slender black flies with a reddish-yellow head and yellowish legs.[1]
  • Larvae are creamy white, tapered maggots that tunnel through the lower third of the root; burrows are often rusty red.[1]
  • Above ground, attacked plants show wilting, discolored ('rusty') foliage, especially in dry weather, and less damaged plants look stunted.[2]

Where it lives

Utah State reports it as sporadic in Utah but economically damaging when present, and the Pacific Northwest handbook covers it as a regional carrot pest.[1][2]

Biology and life cycle

Flies are present from May until harvest, with two to three generations a year.[1]

They overwinter as pupae in the soil or occasionally as larvae in roots.[1]

Damage and signs

  • Young plants may be killed, while older carrots are scarred, and the damage can promote rotting.[1]

Health risk

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

Control

Prevention

Hang yellow sticky cards from late April through the season; Utah State suggests considering treatment at 2 to 3 adults per card.[1][2]

Rotate crops, and destroy volunteer carrots and other plants of the carrot family that may host the fly.[2]

Sanitation

Harvest carrots in blocks rather than selectively, as early as possible, and remove all carrots from the ground after harvest.[1][2]

Traps and physical control

Floating row covers work very well.[2]

Pesticides

The Pacific Northwest handbook lists no products registered for home use against this pest.[2]

Common questions

Why do my carrots have rusty brown tunnels?
Carrot rust fly maggots tunnel the lower third of the root and leave rust-colored burrows.[1]
What is the best way to protect carrots from rust fly?
Floating row covers work very well; also rotate, harvest early and in blocks, and clear old carrots.[2][1]
Is there a spray for carrot rust fly in home gardens?
The Pacific Northwest handbook lists none registered for home use.[2]

Sources

  1. Utah State University Extension, “Carrot Rust Fly.” extension.usu.edu/planthealth/ipm/notes_ag/veg-carrot-rust-fly.php (accessed 2026-10-15)
  2. Pacific Northwest Pest Management Handbooks, “Carrot - Carrot rust fly (Hosts and Pests of Vegetable Crops).” pnwhandbooks.org/insect/vegetable/vegetable-pests/hosts-pests/carrot-carrot-rust-fly (accessed 2026-10-15)
  3. iNaturalist, “Chamaepsila rosae taxon page (order and family).” www.inaturalist.org/taxa/387425 (accessed 2026-10-06)

Updated 2026-10-15. Built from sourced records. Spot an error? Tell us.