A newly published study provides evidence that dust and bioaerosols moved from a commercial poultry operation a short distance downwind into an almond orchard and altered the microbiome recovered from the leaves. Over a 2-year period, drag swabs of orchard soil surface and air, soil, and almond leaf samples were collected in an almond orchard adjacent to (35 m from the first row of trees) and downwind from a poultry operation with 60,000 layers and in two almond orchards (controls) that were surrounded by other orchards. On average, the amount of dry solids on leaves collected from trees closest to the poultry operation was more than 2-fold greater than from trees 120 m into the orchard or from any of the trees in the control orchards. Members of the family Staphylococcaceae—often associated with poultry—were, on average, significantly more abundant in the phyllosphere of trees closest to the poultry operation (10% of relative abundance) than in trees 120 m into the orchard (1.7% relative abundance) or from any of the trees in control orchards (0.41% relative abundance). Salmonella was never detected from any of the 529 air, soil, and drag swab samples. Access to the poultry operation to test manure and litter samples was not granted, and thus, it was not possible to determine if there was any Salmonella was associated with these birds. The report notes that “required setback distances from the edge of concentrated animal feeding operations (e.g., >1,000 cattle or >82,000 poultry layers) to leafy green plantings were increased in 2018 from 120 m (400 ft) to 370 m (1,200 ft) for California and Arizona leafy greens growers.” The study, which was published in the peer-reviewed American Society for Microbiology Journal, was conducted by several researchers: Christopher G. Theofel, Thomas R. Williams, Eduardo Gutierrez, Gordon R. Davidson, Michele Jay-Russell, Linda J. Harris, and editor Donald W. Schaffner.

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