Onion thrips (Thrips tabaci Lindeman) is a major pest in organic onion production and effective integrated pest management strategies are lacking. Our objective was to evaluate combinations of semi-glossy (“Rossa di Milano” and B5336AxB5351C) and waxy (“Bradley”) onion cultivars with reflective mulch, with or without biopesticides (spinosad + neem oil tank mix), to manage T. tabaci in organic onion production. Thrips densities were assessed weekly and bulbs graded and weighed at harvest. Onions sprayed with spinosad + neem oil had fewer T. tabaci (adults: 74% (2019); larvae: 40% (2018), 84% (2019) and produced higher yields (13% (2018), 23% (2019)) than onions that were unsprayed, regardless of mulch type or onion cultivar. “Rossa di Milano” had relatively fewer adult and larval thrips populations compared with “Bradley” (21% (2018), 32% (2019)) and B5336AxB5351C. However, “Rossa di Milano” had the lowest marketable yield in both years. Reflective mulch reduced densities on certain dates in both years compared to white mulch, but the largest and most consistent reduction only occurred in 2019. Reflective mulch had no impact on bulb yield. While spinosad + neem oil reduced thrips numbers and increased yield alone, none of the treatment combinations were effective at suppressing populations of thrips. Future T. tabaci management in organic onions will require optimization of the available effective biopesticides.

Allium leafminer, Phytomyza gymnostoma Loew, is the newest invasive pest of allium crops in North America. Larvae initially feed in the upper canopy before mining toward the base of the plant to pupate. Crop loss occurs when larvae destroy vascular tissue, facilitating infection by bacterial and fungal pathogens that cause rot. Contamination also occurs when larvae and pupae are present at harvest. In response to this invasion, efficacy of 14 insecticide active ingredients applied via foliar sprays, transplant treatments, and drip chemigation was evaluated for managing P. gymnostoma. Multiple field studies were conducted in onions, leeks, and scallions in Pennsylvania and New York, United States in 2018 and 2019. The highest and most consistent levels of P. gymnostoma control occurred using foliar applications of dinotefuran, cyantraniliprole and spinetoram (84–89% reduction in damage; 95% reduction in P. gymnostoma densities). Despite the success of dinotefuran and cyantraniliprole applied as foliar sprays, neither was effective in controlling P. gymnostoma when administered via drip chemigation. Other foliar-applied insecticides that significantly reduced densities of P. gymnostoma in one or two experiments included abamectin, acetamiprid, cyromazine, imidacloprid, lambda-cyhalothrin, methomyl, and spinosad. Active ingredients that never controlled P. gymnostoma included azadirachtin, kaolin clay, pyrethrin, and spirotetramat. Spinosad applied to bare-root and plug-tray transplants immediately before transplanting reduced P. gymnostoma damage in the field by >90%. Implications of using these insecticides and application strategies are discussed within the context of developing a sustainable IPM program.

Onion maggot (Delia antiqua Meigen) control using insecticide treatments to protect transplanted onion was evaluated on muck soil in a commercial onion field south of Oswego, New York (GPS: 43°26′58.5″N 76°23′56.2″W) in 2018. Onion ‘bare-root’ plants, cultivar ‘Bradley’ (Bejo Seeds, Geneva, NY), were transplanted on 16 May. Each plot consisted of two 10-ft-long rows, separated by 15 inches. Plots were separated from each other by a 3-ft alley of bare soil. There were no guard rows. Plants were transplanted at a density of 3 per ft (60 plants/plot). There were four treatments, including the untreated check that were arranged in an RCBD with six replicates.