Biocontrol introduction
Target pest: Galium aparine (Gentianales: Rubiaceae), cleavers
Agent introduced: Cecidophyes rouhollahi (Acariformes: Eriophyidae), cleavers mite
Imported:
Accidental introduction, first recorded in New Zealand in 2017.
Import notes:
Landcare Research (2024i) - accidental introduction. First detection in New Zealand was in Auckland in June 2017, on G. aparine plants displaying extensive curled leaves as a result of the infestation.
Released:
Accidental introduction, first recorded in New Zealand in 2017.
Establishment:
Landcare Research (2024i) - the first detection of C. rouhollahi in New Zealand was in Auckland in June 2017; since then, symptomatic plants have been found throughout New Zealand, from the Bay of Islands in the North Island to Fiordland and Otago in the South Island. Cecidophyes rouhollahi is already so widespread in the country that any question about whether to augment (as a biocontrol agent) or slow (as an invasive species still classified as a 'new organism' in New Zealand under the Hazardous Substances and New Organisms (HSNO) Act) its dispersal is moot.
Impacts on target:
Landcare Research (2024i) - based on observed symptoms, it is assumed that C. rouhollahi is having a big impact on G. aparine in New Zealand. For example, observations indicate it is very common around Christchurch, where it appears to frequently kill plants before they set seed. Several predatory phytoseiid mite species have been found in association with C. rouhollahi in New Zealand, but they don’t seem to have much impact on the ability of C. rouhollahi to gall cleavers plants.
Impacts on non-targets:
Landcare Research (2024i) - Cecidophyes rouhollahi has been released in North America as a biocontrol agent for Galium spurium (false cleavers), a close relative of G. aparine. Specificity testing conducted in France by the US Department of Agriculture indicated that C. rouhollahi could only survive and reproduce on three closely related annual species in section Kolgyda of the genus Galium (although two of those species, G. spurium and G. aparine, have subsequently been transferred to section Aparine). Cecidophyes rouhollahi mite is therefore unlikely to be capable of attacking the Galium species that are native to New Zealand, because these belong to Galium sections (Platygalium and Dioicae) other than Kolgyda and Aparine.
References
Landcare Research (2024i). Accidental introduction of cleavers mite. Weed Biocontrol: What's New? November 2024, 110: 4-5 https://www.landcareresearch.co.nz/publications/weed-biocontrol/weed-biocontrol-articles/accidental-introduction-of-cleavers-mite/
