Puccinia araujiae, a promising classical biocontrol agent for moth plant in New Zealand: Biology, host range and hyperparasitism by Cladosporium uredinicola

- The life cycle and biology of Puccinia araujiae was investigated.
- This rust produces galling on Araujia hortorum, a problematic weed in New Zealand.
- It is sufficiently specific to be used as a biocontrol agent.
- A protocol was developed for the long term preservation of its teliospores.
- Puccinia araujiae is a new host for Cladosporium uredinicola.

The rust fungus Puccinia araujiae is proposed as a biological control agent for moth plant (Araujia hortorum) in New Zealand. This pathogen completes its life cycle on this host, it has the capacity of damaging it by producing premature foliage senescence and defoliation, and, it is only known from members of the Oxypetalinae (Apocynaceae). P. araujiae was found to be heavily hyperparasitised by the fungus Cladosporium uredinicola in the field in Argentina. The mode of action of this hyperparasite was investigated and efforts are currently being made to completely eliminate it from a culture of the rust through a combination of superficial disinfection and multiple sequential inoculations. A protocol was developed for long term storage of teliospores of the rust at very low temperatures. Stored spores were shown to maintain their ability to germinate and produce infective basidiospores for up to 12 months. The possible effect of the hyperparasite on the performance of the rust as a biological control agent, should it be introduced into New Zealand, is discussed.