On Monday Sept.12 2022, Allium leaf miner (ALM) activity was detected in chives growing in Ulster County. Based on the very low level of activity detected so far in our area, and no activity detected at other sites known to have significant ALM populations, we believe that this is the very beginning of the flight that will intensify over the next 3-4 weeks. Fall ALM activity has been observed over an extended duration of up to 8 weeks compared to the typical 6 weeks we see over the Spring ALM flight.  If you plan on managing ALM in your allium crop using floating row cover or insect netting, now is the time to get it on the crop with edges well secured so that there are no gaps for ALM flies to sneak in. Keep in mind that exclusion will not work if infested alliums, including wild onion grass, grew in the same plot the previous season. Check alliums for oviposition marks before covering. If oviposition marks are already visible you may want to consider an insecticide spray.

Based on our observations and reports from growers, it appears that some allium species are more susceptible to damage from ALM over the 8 week Fall flight. Most susceptible are leeks, scallions, and chives. Presence of larvae combined with the cosmetic damage from mining may make these crops unmarketable.  Over the past five seasons, we have generally observed a higher intensity of damage to allium crops from the Fall  ALM flight compared to the Spring flight.

Research we’ve conducted over the past three seasons has shown that planting alliums on metalized reflective plastic mulch consistently reduced ALM damage between 22% to 36% compared to alliums planted on either black or white plastic. Combining the use of metalized reflective plastic mulch with two carefully timed applications of Entrust at the 6 fl.oz/acre rate mixed with M-Pede at 1.5% v:v concentration either 2 and 4 weeks or 3 and 4 weeks after the beginning of the adult ALM flight can be an effective strategy for managing ALM for organic growers. Adding the adjuvant Nu-Film P to Entrust significantly DECREASED the efficacy of the insecticide at managing ALM when compared to combining M-Pede with Entrust.

Several conventional insecticides already labeled for use on bulb crops in New York are effective at reducing damage from ALM, including Exirel (cyantraniliprole, IRAC Group 28, 2(ee) label required and available on the https://www.dec.ny.gov/nyspad/products?3website) at 13.5 fl oz/acre, Radiant (spinetoram, IRAC Group 5) at 8 fl oz/acre, and Warrior II with Zeon Technology(lambda-Cyhalothrin, IRAC Group 3A) at 1.6 floz/acre.

Scout the crop and look for the distinctive ovipostion marks before you set out to spray. ALM pressure will vary from farm to farm and within the Eastern New York Region. Low levels of ALM may not warrant a spray based on the crop you are growing. Furthermore, there are seasonal limits on applications of certain pesticides so you want to use these judiciously.

More information on ALM can be found on our website https://enych.cce.cornell.edu/ including a recent podcast: https://soundcloud.com/easternnewyorkvegnews/allium-leafminer-alm-update. Northeast SARE Progress Report: projects.sare.org/project-reports/one19-336/ details the findings from Rusinek and Grundberg’s research to evaluate row cover and insect netting compared to two applications of Entrust and M-Pede to manage ALM. University of Massachusetts 2020 Pests of the Year ALM Presentation: www.youtube.com/watch?v=IadfeJ1dWVo for the recording and cornell.box.com/s/wbtigjuuc82ufktu1ghfb0b2dh166mk5 for the slides in PDF. ALM Lookalikes and Visual Lifecycle PDF: cornell.box.com/s/q2rdq3vuih5xzoy8dwfu63mm5q980drn.

If you have any questions meanwhile, please feel free to contact Teresa Rusinek at tr28@cornell.edu 845 389-3562 or Ethan Grundberg at eg572@cornell.edu 617 455-1893.