Ants as Predators of Diorhabda elongate (Chrysomelidae), A Biological Control Agent of Saltcedar (Tamarix spp.), in Texas

Four species of leaf beetles, Diorhabda spp, (Chrysomelidae), were introduced for biological control of saltcedar, Tamarix spp., an invasive small tree or shrub, in the US. In Texas, three species established at some sites but failed to establish or initially established but did not persist at other sites. Diorhabda larvae pupate in leaf litter on the soil surface and thus are exposed to ants and other soil-active predators. Predation by ants on Diorhabda pupa was evaluated as a potential factor in limiting establishment of Diorhabda populations at field sites in West Texas. Nighttime observations of pupae found that native ants represented 46-65% and pill bugs (Isopoda: Armadillidiidae) represented 8-51% of observed predation events. The predation rate of Diorhabda pupae by ants was significantly greater where red imported fire ant, Solenopsis invicta Buren, was present. When present, S. invicta was responsible for 93-100% of observed predation during the day. In the absence of S. invicta, native ants Monomorium spp., Crematogaster spp., and Formica perpilosa Wheeler were observed preying on Diorhabda pupae. Results suggested that predation by ants, especially red imported fire ant, could limit establishment of Diorhabda spp. released for biological control of saltcedar.