Female Allium Leafminer making distinct damage pattern. By Tim Elkner
The spring season has begun! At the end of March, we started setting up sticky traps for monitoring the adult flight of the Allium Leafminer in our region. This past week (April 3 to April 9) we had our first damage sighting.
During Dr. Tim Elkner's farm visits yesterday (4/6/17) to set traps, he found evidence of activity of adult allium leaf miner (ALM) at 2 of 3 sites in Lancaster County. The first site had feeding damage on onion transplants being produced in a greenhouse as well as feeding damage on scallions planted in the ground in a second structure. At the second farm, Dr. Elkner noted feeding damage on shallot seedlings being transplanted as well as on wild alliums in the nearby fencerow.
Dr. Elkner's observations suggest that the feeding damage at the second farm was recent - 1 to 2 days at most due to fecal matter being present on the leaves despite rain on Tuesday (4/4/17). There was no evidence of larval feeding at either site. The Fleischer lab also received the first set of sticky traps from 3 farms in Berks County on Thursday (4/6/17). All of the traps were negative for adult ALM captures.
Dr. Tim Elkner posted information today (4/7/17) at the Leola and Weaverland produce auctions in Lancaster. Dr. Shelby Fleischer updated the 1-800-PENN-IPM line on April 6, 2017. For those who may not be aware - we have a dedicated ALM line on the 1-800-PENN-IPM line this season and will be updating it regularly regarding activity of ALM in both the spring and fall.
Currently, ALM has overwintered as a small brown pupa in plant tissue or in the soil where alliums were present in the fall. A sign of adult ALM activity is the distinct ovipositioning/ feeding damage as shown in the image. We expect regional activity to begin within the next few weeks. Dana Roberts had two adult ALM hatch over the weekend of April 8th - 9th, 2017 from field collected pupa. She is suggesting that the adult activity will likely begin the week of April 10th, if it has not already done so.
For those in affected counties this pest is either active (we cannot specify about regional appearance yet - it would be useful to know if/when they become active in your area) or will be soon. Last season Dr. Tim Elkner had numerous growers who were unaware of this pest. Those growers lost all or most of several spring allium crops so ALM can be a significant problem.
For more information about the allium leafminer the Pennsylvania Department of Agriculture and Penn State posted reports and a pest alert to these websites: