The red imported fire ant, Solenopsis invicta Buren, poses a significant threat to biodiversity, agriculture, and public health in its introduced ranges.  While chemicals such as toxic baits and dust are the main methods for S. invicta control, toxic baits are slow, requiring approximately one or two weeks, but dust can eliminate the colony of fire ants rapidly in just three to five days.  To explore more active ingredients for fire ant control using dusts, the toxicity of bifenthrin and dimefluthrin, the horizontal transfer of bifenthrin and dimefluthrin dust and their efficacy in the field were tested.  The results showed that the LD₅₀ (lethal dose) values of bifenthrin and dimefluthrin were 3.40 and 1.57 ng/ant, respectively.  The KT₅₀ (median knockdown time) and KT₉₅ (95% knockdown time) values of a 20 μg mL^–1 bifenthrin dose were 7.179 and 16.611 min, respectively.  The KT₅₀ and KT₉₅ of a 5 μg mL^–1 dimefluthrin dose were 1.538 and 2.825 min, respectively.  The horizontal transfers of bifenthrin and dimefluthrin among workers were effective.  The mortality of recipients (secondary mortality) and secondary recipients (tertiary mortality) were both over 80% at 48 h after 0.25, 0.50 and 1.00% bifenthrin dust treatments.  The secondary mortality of recipients was over 99% at 48 h after 0.25, 0.50 and 1.00% dimefluthrin dust treatments, but the tertiary mortality was below 20%.  The field trial results showed that both bifenthrin and dimefluthrin exhibited excellent fire ant control effects, and the comprehensive control effects of 1.00% bifenthrin and dimefluthrin dusts at 14 d post-treatment were 95.87 and 85.70%, respectively.

In January 2022, we received ant specimens collected from three field colonies from Shantou City, Guangdong Province, China.  They were identified as the little fire ant, Wasmannia auropunctata, through morphological and molecular analyses.  Wasmannia auropunctata is listed as one of the 100 most dangerous invasive species by the International Union for Conservation of Nature (IUCN) and has spread from its native range in South America to every continent except Antarctica.  DNA analysis of mitochondrial cytochrome c oxidase subunit I (COI) in nine specimens of W. auropunctata found that they had a close genetic relationship with specimens from Argentina.  This study represents the first formal record of the establishment of W. auropunctata outdoor in Chinese mainland.  However, the invasion stage and occurrence degree of W. auropunctata in China are not clear to date.  The implementation of quarantine measures, investigation of the occurrence and distribution, and development of monitoring and control strategies are needed to actively respond to the threat posed by this highly invasive ant.

Frequent international trade has accelerated alien species invasion.  However, data on the distribution of invasive species after their introduction and research on the factors that determine their geographical distribution are lacking.  This study analyzed the distributional trends of invasive species in China and the drivers for such trends, by identifying the effect of international trade from a dynamic analysis of 13 main invasive insect pests in three time periods – before China’s reform and opening up in 1978, from 1979 to 2001, and after China’s accession to the World Trade Organization in 2001.  The results showed that the abundance of invasive species gradually decreased from south to north and from southeast coast to inland.  Guangdong (442 species) and Yunnan (404 species) provinces have the highest abundance of invasive species.  Among the 13 key invasive insects investigated, 3, 10 and 13 occurred chronologically in the three periods, and invaded 7, 28 and 34 provinces, respectively.  Alien pests are found to invade China through Xinjiang, the Bohai Rim and the southeast.  Value of imports was a strong predictor of the number of invasive species in China, and followed by temperature heterogeneity, in explaining the richness pattern of invasive animal, plants and insects, but not that of microorganisms.  This study provides a scientific basis for furthering international quarantine and effective invasive species control.