Tree covers that exclude foliar pests alter the soil microbiome and reveal potential bacterial antagonists of diaprepes root weevil

Diaprepes root weevil (DRW, Diaprepes abbreviatus) is a New World pest of citrus trees. Biological control by native entomopathogenic nematodes (EPN) has been proposed as a driver of DRW abundance across Florida’s ecoregions. Weevils also typically occupy specific locations within orchards for unknown reasons. To identify potential causes of local weevil patterns, we measured relationships between DRW and edaphic properties in an orchard in which half the trees were initially protected from foliar herbivores by individual protective mesh covers (IPC). Weevils were monitored for two years in 94 plots arranged in a grid pattern. Soil samples were processed for physicochemical properties and metabarcoding of ITS2 rDNA, 16S rDNA, and COI mtDNA. Soil moisture, Paenibacillus spp. diversity, and IPC were associated with DRW patterns and tree mortality. Species in the dominant prokaryote classes and phyla (Bacilli, Actinobacteria, Alphaproteobacteria, Cyanobacteria) that were affected by IPC use were less abundant on formerly covered trees and inversely related to weevil abundance and tree mortality. The multiple services provided to plants by bacteria in these major groups suggest a need for continued study of how IPC may modulate the rhizosphere food web and tree health. Paenibacillus sp. JF317562, an ectoparasite of the entomopathogenic nematode Steinernema diaprepesi, was the only one of 92 detected Paenibacillus species correlated with that nematode. Spatial associations between Paenibacillus sp. JF317562 and several other detected nematode species support its characterization as a specialized associate of entomophilic nematodes having a suite of symbiotic relationships. ranging from commensalism to parasitism.