Alliums interplanted with carrots reduce carrot rust fly damage.
A good hunch A person has checked it against its sources. If you skip this, it still grows, just less well. The planner suggests it.
How it works
The carrot rust fly finds its host by the smell of carrot foliage. Onion and other allium volatiles growing among the carrots mask that scent, so fewer flies locate the row to lay eggs. Because the protection is the smell, it lasts only while the alliums are in the ground. Once they are pulled, the masking goes with them.
How much it matters: Modest; protection collapses once alliums are harvested.
The evidence
Evidence: checked against 1 source in the research-based literature.
The source
Intercropping with onion has been shown to reduce damage by carrot rust flies.
Plant teams that rest on it
Folklore it answers
Read next
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How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Sources updated
- Wording made clearer
- How it works updated
- A person read the sources and confirmed it
- Added to the rules
Plan a bed with Carrot, chive and lettuce ›
Companion planting charts encode real relationships. · What can I plant now?
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Cite this page
Milpa Gardens. “Alliums interplanted with carrots reduce carrot rust fly damage.” Evidence grade: A good hunch. https://milpa.garden/rules/alliums-interplanted-carrots-reduce-carrot-rust-fly/
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How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
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- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.