African lovegrass

The NSW Environmental Trust is one of the cash contributors to the national project ‘Underpinning agricultural productivity and biosecurity by weed biological control’ supported by the Australian Government programme Rural Research and Development for Profit (RRnD4P) (Round 4) administered by the Department of Agriculture, Water and the Environment. The three-year project (to June 2022) is led by AgriFutures Australia, focuses on 11 different weed targets and includes researchers from four agencies with capabilities and infrastructure to undertake weed biocontrol research in Australia (CSIRO, NSW Department of Primary Industries, Queensland Department of Agriculture and Fisheries and Victoria Department of Economic Development, Jobs, Transport & Resources).

African lovegrass (Eragrostis curvula) is one of the weed targets in which the NSW Environmental Trust is co-investing. Kerinne Harvey of NSW Department of Primary Industries is leading this sub-project, which involves collaborators from Rhodes University in South Africa.

African lovegrass has never been a target for biocontrol anywhere in the world. This project is focusing on key initial stages to assess prospects for implementing a biocontrol program for this weed in Australia.

Planned activities

1. Nominate African lovegrass as a suitable candidate species for biocontrol research in Australia.
2. Conduct surveys in southern Africa for natural enemies associated with African lovegrass.
3. Conduct preliminary host range testing of promising natural enemies for African lovegrass.

Progress

2020/21

The draft document to nominate African lovegrass as a target for biocontrol was revised to include findings from a recent phylogenetic study. A behavioural national survey has been developed to identify any substantive conflict between the detrimental impacts of African lovegrass as a weed and any economic use or other useful attributes. Once human ethics approval is granted, the survey will be virtually conducted, and results incorporated into the nomination document before submission to the national Environment and Invasives Committee.

A preliminary plant list for host-specificity testing has been compiled to guide the screening of potential biocontrol agents. Four potential agents were identified during field surveys in the native range, South Africa. These include two undescribed stem-boring herbivorous wasps (Hymenoptera: Eurytomidae), a shoot-galling fly (Diptera: Chloropidae) and a gall-midge (Diptera: Cecidomyiidae).

DNA barcoding confirmed that the two wasps belong to the Tetramesa genus. Cultures of three of these candidate agents were established in the greenhouse in South Africa. Preliminary no-choice testing showed that the shoot-galling fly was able to complete development on two non-target grasses outside of the Eragrostis genus. No-choice testing is on-going with each of the Tetramesa wasps, although one of these has been recorded on two non-target South African Eragrostis species in the field. The other Tetramesa wasp, which was only found on African lovegrass during field surveys, did not complete development on any of the non-target grasses tested thus far.

2019/20

Draft document to nominate the weed as a target for biocontrol was completed. Compilation of a list of stakeholders was initiated and a draft survey questions circulated to biosecurity officers and internal NSW DPI staff for feedback before finalisation. Results from this survey will be part of the nomination document. Native range surveys for candidate agents in South Africa have not yet started.