Allium leafminer is an invasive insect from Europe that found its way to North America in December 2015.
Since that first U.S. sighting in Lancaster County, Pennsylvania, ALM has spread to surrounding states and has caused damage and even total crop loss on fields of vegetables in the allium family, including spring onions, garlic and leeks.
We have been studying this insect since 2016 to understand its biology and provide management recommendations.
ALM has two flights per year (spring and fall) and each flight lasts from four to eight weeks. I have observed that ALM does not always appear in damaging numbers in any given field. One season a grower will have a high population, and the next will see only sporadic damage. Unfortunately, there is no way to predict what the population will be at any given location, so allium growers need to scout their crops and apply appropriate control measures as needed.