Engytatus passionarius (Hemiptera: Miridae), a Potential Biological Control Agent of the Invasive Vine Passiflora foetida (Passifloraceae) in Australia

Abstract

Passiflora foetida senso lato L. (Passifloraceae), native to the Americas, is an invasive vine impacting areas of environmental, economic, cultural and social importance across northern Australia. The leaf-sucking mirid, Engytatus passionarius Minghetti, Maestro and Dellapé (Hemiptera: Miridae), was recently described and identified as a potential biological control agent of P. foetida following native range surveys in northwestern Argentina. Its biology and host range were investigated in Argentina and under quarantine in Australia to assess its suitability for release. Host specificity was initially evaluated in the native range through field host range observations, laboratory studies assessing zoophagy and no-choice tests on available Passiflora species. These studies indicated a high level of specificity to P. foetida, supporting further evaluation in Australian quarantine. Comprehensive no-choice host specificity testing included 31 plant species selected based on their phylogenetic relationships to the target weed spanning the Passifloraceae, Salicaceae, Achariaceae, Violaceae, Euphorbiaceae and Phyllanthaceae. Feeding, oviposition and successful development to adulthood occurred consistently on P. foetida. Survival rates were significantly higher on the target weed than on nontarget plant species, where individuals experienced markedly increased mortality. Feeding on nontarget plants was generally low and exploratory, whereas consistent vegetative damage occurred on P. foetida. Developmental success for the mirid was also substantially reduced on nontargets (mean 0.2–4.6 F1 adults) compared with P. foetida (mean 52.5 F1 adults). Six nontarget Passiflora species were further evaluated in choice tests. E. passionarius consistently preferred P. foetida, initiating feeding more rapidly and producing higher nymph densities than on nontarget species. Completion of the life cycle occurred only on P. foetida. Overall, results from native-range studies, quarantine experiments and field observations demonstrate that E. passionarius is highly host-specific to P. foetida and represents a promising candidate for biological control in Australia.