Highlights
A promising biological control agent identified: Research pinpointed Neoleucopis n. sp. B as the most suitable predator of giant pine scale (GPS), showing strong preference for the pest and minimal risk to non‑target native insects.
High prey‑specificity gives confidence in safety: Field and laboratory studies found the predator rarely, if ever, attacked other scale species, strengthening its potential safety profile for Australian ecosystems.
Critical groundwork completed for future release: Scientists established rearing methods, clarified species genetics, and prepared a draft regulatory submission – key steps toward potential approval for release.
Potential long‑term benefits for industry: If approved, a biological control agent could reduce GPS impacts on Pinus radiata plantations, helping protect tree health, reduce spread, and support a more sustainable, non‑chemical management strategy.
Further testing still required: Additional host‑specificity and ecological studies are needed before any release can occur.
Purpose of the research
Giant pine scale (GPS), Marchalina hellenica, is an invasive insect first detected in South Australia and Victoria in 2014. It can cause poor tree health, reduce insect biodiversity, and poses a significant threat to Australia’s softwood industry. This research aimed to understand whether a natural predator—Neoleucopis species (a type of silver fly)—could be safely and effectively used as a long‑term biological control option for GPS in Australia.
The project focused on:
- Identifying which Neoleucopis species occur in the pest’s native range (mainly Greece).
- Assessing which species might be safe to release in Australia (with minimal risk to non‑target native insects).
- Developing rearing methods and gathering ecological information to support a potential future release application.
Benefits to the forestry industry
While no biological control agent is yet approved for release, this research lays the groundwork for a potential long‑term management tool. If regulatory approval is achieved, biological control could:
- Help reduce the spread and impact of GPS in pine plantations—especially Pinus radiata, the dominant commercial softwood.
- Provide a sustainable, non‑chemical option that complements existing management practices.
These benefits remain provisional until further testing and approvals occur.
Key findings
- A promising predator identified: Among three closely related Neoleucopis species found in Greece, one—Neoleucopis n. sp. B—showed strong preference for GPS in both field and laboratory studies.
- High prey‑specificity observed: N. n. sp. B rarely attacked a closely related Australian native scale insect (Icerya purchasi) under controlled conditions and was not observed attacking it in the field, even where both species co‑occur.
- Genetic clarity achieved: DNA analysis confirmed the existence of at least three distinct Neoleucopis species, reducing uncertainty around identification and improving confidence in species‑level risk assessments.
- Rearing protocols developed: Methods for collecting, rearing, and maintaining the fly were established in Greece and adapted for quarantine use in Australia.
- Regulatory preparation completed: A draft application for the potential release of N. n. sp. B has been prepared, pending completion of further testing.
Future research and next steps
To progress toward a potential biological control release, the report recommends:
- Further testing of all three candidate species (N. kartliana, N. n. sp. A, and N. n. sp. B) to compare their safety and effectiveness.
- Additional prey‑specificity studies on Australian native scale insects to ensure minimal risk to non‑target species.
- Continued ecological and efficacy studies in Greece to strengthen understanding of predator–prey dynamics in natural conditions.
- Maintaining cultures of Australian native non‑target insects for future testing.
- Undertaking pre‑introduction monitoring of GPS populations in Australia to help select suitable release sites and establish baseline conditions.
