Native range surveys of Prosopis L. (Fabaceae) in the southwestern United States reveal potential biological control agents

Several species of mesquite, Prosopis spp., are considered weedy in arid and semi-arid regions worldwide, including in Australia and southern and eastern Africa. Despite current control efforts, Prosopis coverage in South Africa has expanded rapidly over the past 15 years. As a result, there is interest in increasing the supply of biological control agents against Prosopis species in South Africa. Successful importation biological control of weeds is based on the collection and identification of appropriate host specific agents during native range surveys. Over 2 field seasons, we used multiple methods, including visual surveys, blacklighting, and beating of foliage to collect arthropods on Prosopis and related trees, including Vachellia, Mimosa and Senegalia species. Surveys were conducted across the southwest United States, including California, Arizona, New Mexico, and Texas. We collected and identified over 2000 individual insects. Coleoptera was the most well represented order among our specimens, with over 1000 individuals across 17 families. We also collected Lepidoptera representing eight families, as well as nine families of Hemiptera. To prioritize host-range testing, we developed a matrix to rank potential biological control agents for Prosopis. We ranked insects according to their ability to damage host plants, host specificity, feeding guild, abundance and prevalence. Based on our field notes and published literature, we identify the insects with the most potential to damage or kill Prosopis species.