Dealing with Carrot Rust Fly in a Hydroponic System
What Carrot Rust Fly Does
Carrot rust fly larvae tunnel into carrot roots, causing feeding galleries that deform and stunt roots, reduce yield, and open pathways for secondary infections. [1]
Latin Name
Psila rosae [1]
Identification
- Adults: shiny black flies, ~6 mm long, with transparent wings, yellow legs, reddish head, and "hunch-back" thorax [1]
- Larvae: white-yellow maggots, ~6-7 mm long, that bore narrow winding tunnels in lower two-thirds of roots [1]
- Root symptoms: stunted, malformed roots with internal galleries
Alternative Names
- Carrot fly
- Carrot root fly
- Carrot maggot (larval stage)
Varieties (Related Species)
- Psila rosae - primary species on carrots
- Psila liriodendri - less common on carrot relatives [4]
Climates Where They Thrive
- Cool, moist regions (12-20 °C) with moderate humidity; peak adult flights in late spring and again in mid-summer [1]
- Poor survival above 25 °C or in very dry conditions (RH < 50 %) [1]
Companion Planting as Deterrents
| Cultivar | Hydroponic Methods | Effectiveness |
|---|---|---|
| Onion (Allium cepa) | Drip, Ebb & Flow, DWC, NFT | High - sulfur volatiles repel adults [2] |
| Garlic (Allium sativum) | All methods | High - strong sulfur compounds deter egg-laying [2] |
| Marigold (Tagetes spp.) | All methods | Moderate - root exudates inhibit larvae [3] |
| Dill (Anethum graveolens) | NFT, Drip | Low - masks carrot scent [4] |
Natural Predators
- Ground beetles (Carabidae) that consume larvae in media [1]
- Parasitic wasps (Trybliographa rapae) attacking larvae [2]
- Rove beetles (Staphylinidae) hunting pupae [1]
Remedies
| Treatment | Hold Period | Natural? | Effectiveness |
|---|---|---|---|
| Floating row covers | 0 days | Yes | High - prevents adult access and egg-laying [1] |
| Bacillus thuringiensis (spinosad formulations) | 3 days | Yes | Moderate - larval toxin in root zone [2] |
| Beneficial nematodes (Steinernema feltiae) | 0 days | Yes | Moderate - infects larvae in media [1] |
| Sticky traps (yellow) | 0 days | Yes | Low - monitoring and some adult capture [1] |
| Soil/media solarization (warm water flush) | 0 days | No | Low-Moderate - heat shocks pupae in media |
Other Remedies
- Hydrogen peroxide flush: Brief 3 % H2O2 treatment to disinfect roots and kill larvae in solution [3]
- Reflective mulch: Line trays with aluminum film to confuse adults [3]
- UV-LED traps: Low-intensity UV light to attract and trap adults at emergence points [2]
Tips and Tricks
- Monitor adult emergence with yellow sticky cards in early spring [1]
- Time planting after first generation flight (late spring) to reduce egg-laying [1]
- Maintain clean system-remove debris that could harbor pupae
- Rotate host crops or fallow hydroponic basin between carrot cycles
Common Hosts
- Carrots (Daucus carota)
- Parsnips (Pastinaca sativa)
- Celery (Apium graveolens)
- Parsley and dill (Coriandrum & Anethum)
- Other Apiaceae family members [4]
Citations
- [1] Carrot Rust Fly IPM Guide (BC Small-Scale Farmer's IPM Guide, March 2021) - https://www.bcclimatechangeadaptation.ca/app/uploads/FI26-Carrot-Rust-Fly-2021-IPM-guide.pdf
- [2] Carrot Rust Fly Biology & Management - Oregon State University Small Farms Program - https://smallfarms.oregonstate.edu/carrot-rust-fly-biology-management
- [3] Combat This Carrot Killer Using a Few Simple Tricks - EarthEasy - https://learn.eartheasy.com/articles/carrot-rust-fly-combat-this-carrot-killer-using-a-few-simple-tricks/
- [4] Enemy: Carrot Rust Fly - Bug Forums at Permies - https://permies.com/t/1109/Enemy-Carrot-Rust-Fly
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