Tube locations of the red imported fire ant (RIFA)

Solenopsis invicta Buren, also known as the red imported fire ant (RIFA),
has had a large negative impact on human and livestock health. However,
few studies have further investigated the influence of human land use,
which is an important factor affecting the habitats of insects, on the
expansion of RIFAs. In addition, there is a lack of knowledge of the
empirical associations between RIFA diffusion and land use within
countries. Therefore, the objectives of this study were to provide an
approach to delineate the areas of RIFA infestations and explore how
land-use influences the spatiotemporal diffusion of S. invicta. We used
RIFA data from 2008 to 2015 from the RIFA surveillance system, which was
conducted by the National RIFA Control Center in Taiwan. Two regions in
Taiwan with different RIFA infestation levels were investigated. The
ordinary kriging method was applied to show the spatial intensity of RIFAs
and the extreme distance estimator method was applied to determine the
critical dispersal distances which showed the distance of the highest
probability of RIFAs in two consecutive years. In addition, network
analyses were used to identify RIFA invasion routes between land-use
types. Finally, bivariate local indicators of spatial association were
used to capture the invasion process in time and space. The results showed
paddy fields, main roads, and warehouses were identified as the top three
land-use types of diffusion sources. On average, the critical RIFA
dispersal distances were 600 and 650 m in two consecutive years in high-
and low-infestation regions, respectively. Finally, RIFAs were likely to
diffuse between main roads and warehouses in the low-infestation region.
Therefore, it is suggested that RIFA control activities be implemented at
least 600 m from the observed spot. Additionally, control activities
should be conducted on the identified three land-use types of diffusion
sources in the high-infestation region, and the roadsides between main
roads and warehouses in the low-infestation region to prevent the
accidental spread of RIFAs.