Impact of Reducing Synthetic Chemical Inputs on Pest and Disease Management in Commercial Onion Production Systems

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Onion production is reliant on synthetic chemical inputs such as fertilizer and pesticides to ensure its profitability. In the Great Lakes region (USA), onion thrips (Thrips tabaci) and a complex of bacterial pathogens that cause bulb rot disease threaten the sustainability of onion production. The potential exists for reducing T. tabaci infestations and bulb rot disease incidence in onions by decreasing the amounts of fertilizer applied at planting and the insecticide applied to foliage during the season. In a three-year study that included 20 New York commercial onion fields, the impact of synthetic fertilizer (no fertilizer, half rate, and full rate) and insecticide use (action threshold-based application program and weekly application program) on T. tabaci populations and bulb rot disease incidence was examined. Results indicated that the amount of fertilizer applied to an onion at planting had no impact on T. tabaci population levels, bulb rot disease incidence, or onion bulb size and yield. In contrast, insecticide use had the greatest impact on reducing T. tabaci densities. Both the action threshold-based program and weekly spray program reduced T. tabaci infestation levels below the economic injury level, but the action threshold program averaged 2.3 fewer applications per season. The insecticide program had no effect on bulb rot incidence, bulb size, or yield. We conclude that synthetic fertilizer and insecticide inputs can be reduced substantially without compromising onion bulb yields, and this should lead to greater profits and a reduction of chemicals in the environment.