Phoretic mites associated with ambrosia beetles in Florida avocados and their potential use in IPM

Ambrosia beetles are wood-boring insects that carry and farm symbiotic fungi using the xylem of the host tree. The fungus Harringtonia lauricola causes laurel wilt, a deadly disease that affects lauraceous plants in native forests, and avocado trees in Florida. The cryptic living habits of these beetles make their management challenging. A few organisms inhabit their galleries, including phoretic mites. Little is known about the ecology of phoretic mites and their potential application in pest management. A survey of phoretic mites on ambrosia beetles was conducted in eight avocado orchards in South Florida. Ambrosia beetles were captured using (1) Lindgren traps, (2) as they emerged from infested logs, and (3) physically excavated from avocado logs. Eleven mite species in six families were collected from nine beetle hosts. The mite family Pygmephoridae was the most abundant. Four new species were found: B. floridensis, Pediculaster sp., Dendrolaelaps sp. and Proctolaelaps sp. The phoretic associations were not specific. Histiogaster arborsignis is a cosmopolitan phoretic mite commonly associated with wood-boring insects. This fungivorous mite can be easily mass-reared and could transport fungal spores to beetle galleries. The fungal feeding plasticity of H. arborsignis was assessed through no-choice assays offering ambrosia beetle fungal symbionts, and two commercially available beneficial fungi. H. arborsignis reproduced for two generations on all beetle symbionts. No reproduction on beneficial fungi was observed. The mites showed a close association with the beetle fungal symbionts and the potential to be incorporated into innovative IPM practices for managing wood boring pests.