Biocontrol introduction

Target pest: Hypericum androsaemum (Malpighiales: Hypericaceae), tutsan

Agent introduced: Melampsora hypericorum (Pucciniales: Melampsoraceae), tutsan rust

Import notes:

Gourlay et al. (2014) - Melampsora hypericorum was first recorded in New Zealand in the early-1950s. It is not known how the rust reached New Zealand.

Released:

Gourlay et al. (2014) - self-introduced; first recorded in New Zealand in the early-1950s.

Establishment:

Landcrare Research (2019) - there are two main strains of the rust present in New Zealand, with one type in the South Island and the other in the North Island. Stewart Island has both.

Impacts on target:

Gourlay et al. (2014) - the impact of M. hypericorum in New Zealand is highly variable. The reason for this is not known; however, H. androsaemum is a polyploidy plant (i.e. it has variable numbers of sets of chromosomes) and this could be the reason for its inconsistent impact.

Landcare Research (2019) - tutsan rust appears to be controlling tutsan in the South Island, where the plant is not invasive, but not in the North Island. There are four genotypes of tutsan present in New Zealand, although two of these are rare. The two common genotypes, like the two rust genotypes, are mainly divided between the North and South Islands. Testing in Europe has shown the North Island tutsan genotype to be resistant to all of the four strains of the rust found in Europe (which includes the two found in New Zealand). This helps to explain why tutsan is problematic in the North Island but not in the South Island.

References

Gourlay H, Rendell E, Olsen E, Groenteman R, Probst C, Padamsee, M, Bellgard S, Goeke D (2014). The results of surveys and DNA analysis of tutsan (Hypericum androsaemum) and tutsan rust (Melampsora hypericorum) in New Zealand and Europe. Proceedings of the XIV International Symposium on Biological Control of Weeds, Kruger National Park, South Africa, 2-7 March 2014

Landcare Research (2019d). Final phase for tutsan project. Weed Biocontrol: What's New? 88, May 2019. https://www.landcareresearch.co.nz/publications/newsletters/biological-control-of-weeds/weed-biocontrol-issue-88/final-phase-for-tutsan-project