On Friday March 29, 2024, Allium leafminer (ALM) activity was detected in a patch of cultivated chives growing in an Ulster County garden. This is the earliest we have detected ALM in the Hudson Valley.  Two weeks earlier ALM damage and adults were seen in high tunnels and overwintered onions in low tunnels, also in Ulster County. Based on the very low level of activity detected so far in the Hudson Valley (except for alliums overwintered in high tunnels), we believe that this is the very beginning of the ALM flight that will intensify over the next 3-4 weeks. 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. If you are transplanting alliums over the next 4-5 weeks, you will want to cover right after you finish planting. It doesn’t take ALM long to find a host crop. 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. 

Over the past five growing seasons, we have generally observed a lower intensity of damage to allium crops from the Spring ALM flight compared to the Fall flight. Based on our observations and reports from growers, it appears that some allium species are more susceptible to damage from ALM over the 6–8-week spring flight. Most susceptible are scallions, and chives, particularly because of the mining and cosmetic damage to tops. Damage in transplanted onions and garlic is less common, however, in the past low numbers of pupae and larvae have been found in the bulb area at harvest.  

Research we’ve conducted over the past four years 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.  Note that for resistance management purposes, the Entrust label allows a maximum of two applications before switching to a different insecticide chemistry/mode of action.   If further control is warranted after two Entrust sprays, consider an application of the insecticide Azera (Azadirachtin + Pyrethrins). Research we conducted in the fall of 2022 on scallions showed that the addition of Azera to a well-timed sequence of insecticide sprays of Entrust can further reduce ALM density in scallion at harvest.  The decrease in ALM density resulting from adding two Azera applications to two Entrust applications can be enhanced by using a spreader/penetrant type adjuvant such as OROBOOST (OMRI listed) that maintains the tank mix solution below pH 7.    

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://extapps.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.  

The Northeast SARE Progress Report: https://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  https://cornell.app.box.com/s/wbtigjuuc82ufktu1ghfb0b2dh166mk5 for the slides in PDF. ALM Lookalikes and Visual Lifecycle PDF: https://cornell.app.box.com/s/rcknozr8ddy5jbm9668gmffqiqbhhw0p

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