Spatiotemporal infestation patterns of Aceria litchii Keifer (Acari: Eriophyidae) in a lychee orchard in South Florida.

The lychee erinose mite (LEM), Aceria litchii, is an invasive eriophyoid mite posing notable risks to lychee (Litchi chinensis) production worldwide. First detected in Florida’s Lee County in 2018, LEM has since spread to all lychee producing counties in the state. This study investigated LEM’s dispersal dynamics following its initial detection in a lychee orchard in Homestead, Florida. A total of 190 lychee trees (‘Brewster’, ‘Mauritius’, and ‘Sweetheart’ cultivars) were monitored bi-weekly to detect new infestations and determine the LEM spread within the orchard and in the canopy of each tree. The overall LEM spread across cultivars, the infestation levels per tree, the colonization patterns within each canopy, and the spatiotemporal dispersion dynamics of LEM within the orchard were evaluated. Factors such as wind direction, temperature, cultivar susceptibility, tree height, flushing, flowering, and fruiting intensity were analyzed for their influence on LEM dispersion. LEM infested the first 10% of the trees in 78.6 days, with the following 90% of the infestation occurring exponentially over the next 100 days. LEM infestation level was significantly linked to the nearest affected tree within the orchard, canopy structure and tree height, suggesting a preference for short-distance (ambulatory movement) over long-distance dispersal (wind and phoresy). The progression of LEM within and between trees correlated with rising temperatures, flushing, and flowering intensity, suggests that dispersion through phoresy using pollinators may have also occurred. ‘Brewster’ was less susceptible to LEM infestation compared to ‘Mauritius’ and ‘Sweetheart’. The relevance of these findings is discussed.