allium leaf miner - Ask Extension
I would like to know the GDD for this insect. It destroyed my leeks last year. I know it emerges and lays eggs in late spring but am wondering if the ...
Knowledgebase
allium leaf miner #925339
Asked March 03, 2026, 10:40 AM EST
I would like to know the GDD for this insect. It destroyed my leeks last year. I know it emerges and lays eggs in late spring but am wondering if the GDD timing is known.
Cuyahoga County Ohio
Expert Response
Allium leafminer (ALM) adults emerge in early spring when 250-350 Growing Degree Days accumulate (base temp 39 degrees Fahrenheit), typically coinciding with forsythia and daffodil bloom. This can be expected between late March and mid April.
The following Penn State Extension publication details ALM emergence projections from the 2025 growing season Allium Leaf Miner on Track to Emerge in Early April.
You may also want to visit the webpage that houses OSU's Phenology Calendar GDD - Calendar.
Hope this helps!
