Carrot fly
Psila rosae
Role in the garden
Larvae boring galleries into the roots, making carrots inedible and encouraging rot.
How to attract / manage it
Fleece from sowing, delayed sowing and scented companions.
Practical guide
Prevention
An insect fleece laid from sowing. Late sowing (after mid-May). Interplanted onion (partial effect, mostly when young); leek, rosemary or chives by tradition. Avoid thinning in mild weather (the scent attracts the flies).
Early signs
Foliage reddening then yellowing; brown, winding galleries in the roots when lifted.
Sources
- RHS (Royal Horticultural Society) : Carrot fly (rhs.org.uk/biodiversity/carrot-fly)
- Uvah, I.I.I. & Coaker, T.H. (1984). Effect of mixed cropping on some insect pests of carrots and onions. Entomologia Experimentalis et Applicata, 36(2), 159-167.
Favourite plants / resources
Related plant entries
Carrot
In the vegetable garden, the carrot is planned first and foremost around its pest, the carrot fly, hence the value of interplanting it with onions. Its taproot needs loose, deep, stone-free soil (RHS), without a heavy application of manure just before (GAB/FRAB Bretagne). And when left to flower, this umbellifer opens up umbels that feed hoverflies and other small beneficials, like the other Apiaceae so valued for drawing in pollinators and aphid predators.
Celery
An Apiaceae with a long growing season (5-6 months) that needs soil very rich in organic matter and sustained watering. The celery-cabbage pairing is traditional: its scent would confuse the olfactory trails of cabbage pests (the cabbage white). Not before carrot (same family).
Parsnip
Its taproot needs deep, loose, stone-free soil (RHS); in this site's rotation, parsnip comes before the legumes. Its umbel flower, in the second year, feeds hoverflies and small beneficial hymenoptera.