B.WEE.0148 - Integrated management and development of additional agents for Parkinsonia

Summary

The project aimed to control the invasive Parkinsonia aculeata, a shrub/tree species causing significant ecological and economic damage in northern Australia, that can incur control costs between $2–$300/ha/y depending on the density of infestations, by releasing an approved leaf-defoliating biological control agent which had not yet received substantial release effort. Also, developing tools to assist with the monitoring and evaluation of the two closely related leaf-defoliating agents once they were established across northern Australia.

Objectives

1. This project aimed to build on previous research investments made into Parkinsonia management by focusing rearing and release efforts on Eueupithecia vollonoides.
2. To simplify the identification process of the morphologically identical moth agents, molecular tools were developed. These molecular diagnostic tools have become increasingly important in monitoring establishment and impacts of agents, and to determine where each moth species has established relative to one another.
3. Chemical components of the female sex pheromones of E. vollonoides and Eueupithecia cisplatensis were characterised to determine if a pheromone lure that could be deployed for monitoring and aggregating populations of the agents across northern Australia.
4. The final component of the project focused on investigating the applicability of an additional weed biocontrol agent with a different mode of action to existing approved agents for P. aculeata.

Key findings

Based on the surveys presented both E. cisplatensis and E. vollonoides (leaf defoliating moths) have established self-sustaining populations across the range of Parkinsonia in northern Australia and there is evidence these populations are moving across the landscape. However, ten years after initial releases commenced, population densities of both moth species are not yet at the levels determined by laboratory studies to start chronically defoliating and stressing trees.

Native range and quarantine research on another stem-galling biocontrol agent was undertaken with a focus on evaluating approaches to colony initiation under quarantine conditions.

Benefits to industry

The key benefit to the pastoral industry is the presence of two additional leaf-defoliating moth biological control agents as a persistent landscape scale weed management tool in the integrated weed management toolbox for parkinsonia. This will enable land managers to prioritise where in the landscape they can deploy other management tactics.

MLA action

This project (B.WEE.0148) extended this pipeline of research by; 1) releasing additional leaf defoliating biological control agents (risk assessed during project B.NBP.0620, and commenced releases in projected B.WEE.0134 & B.WBC.0060) 2) developing new tools to ease the monitoring of their establishment and, 3) investigating an additional stem-galling fly that was identified as a potential agent in B.NBP.0366.

Future research

Based on the results of the project, further native range and quarantine risk assessment to develop an additional weed biocontrol tool for Parkinsonia should be undertaken to build on the knowledge of N. aculeata (stem galling fly) gained during B.WEE.0148. Any future research on N. aculeata should be focused on further understanding the ecology of the galling insect so that it can be reared under Australian quarantine conditions and undergo host-specificity testing.

Because Parkinsonia is such a widespread weed across the rangelands of northern Australia, monitoring and evaluation of weed management would be enhanced if cost-effective, scalable and accurate approaches are developed. This includes building on the development of pheromone-based tools for E. vollonoides and E.cisplatensis which can monitor the presence of these agents but may also be able to aggregate them into areas of high weed density.