The Allium leaf miner (Phytomyza gymnostoma) is an invasive fly pest that damages crops by laying eggs in their leaves like:
- chives
- garlic
- leeks
- onion
- shallots
- wild garlic
The resulting maggots tunnel down into the stems and bulbs, causing wilting, distorted growth and leaving plants susceptible to bacterial/fungal infections, leading to significant crop loss, especially affecting storage quality.
The pest has been found to have two generations per year, with activity in the spring and again in the fall (summer aestivation or inactivity). The allium leaf miner overwinters as a pupa within plant tissue.
Report allium leaf miner sighting
Where it is
Of European origin, the Allium leaf miner has been identified in several U.S. states representing the first records in the Western Hemisphere.
U.S. states with Allium leaf miner and year of detection
- Delaware (2019)
- Maryland (2017)
- Massachusetts (2019)
- New Jersey (2016)
- New York (2017)
- Pennsylvania (2015)
The allium leaf miner was first described in Poland in 1858, with subsequent finds in other European countries, but it has only emerged as a significant pest since the late 20th century.
How to spot it
-
Larvae -
Pupae -
Adult -
Egg laying scars
Larvae:
- are cream to yellowish in colour
- measure up to 8 mm (3/8 inches) in length
- legless
- lack a distinct head capsule
- have two elongated lobes or projections at one end
Pupae:
- are roughly 3.5 mm (approximately 1/8 inch) long,
- oval or bullet-shaped
- dark brown to reddish-brown in color
The adult:
- is very small, 3 mm (approximately 1/8 inch) long
- is grey to black fly with a yellow head
- has yellow markings at the leg joint-or yellow 'knees'
Females create punctures before egg laying and both males and females can be observed feeding on the plant exudates seeping from these wounds. Spots follow a distinct line.
Larvae and pupae can be found by pulling leaves apart and looking between the leaf layers.
As they grow, larvae move towards the bulb and sheath leaves, where they pupate. The galleries in the tissue leave the plant susceptible to infection by fungi and bacteria.
What we are doing
The allium leaf miner is a regulated pest in Canada. When allium leaf miner is detected, official control measures may be put in place to prevent its spread.