Native saltbush (Rhagodia spp.; Chenopodiaceae) as a potential reservoir for agromyzid leafminer parasitoids on horticultural farms

Australia has to date been spared the introduction of highly polyphagous invasive pest agromyzid leafminers; however, their arrival and spread should be considered imminent. To develop a pre-emptive control strategy to deal with exotic leafminer outbreaks the first step is to identify Australian leafmining flies, their plant hosts and their parasitoids to gain an understanding of their population dynamics. Native vegetation may be providing resources for beneficial parasitic wasps plus access to alternative hosts and refuge from disturbance. Here, two Australian endemic saltbushes ( Rhagodia candolleana and R. parabolica , Caryophyllales: Chenopodiaceae) have been investigated for their potential to act as reservoirs for endemic agromyzid hosts and their key parasitoids. Mined leaves of the two Rhagodia species were sampled on two commercial horticultural properties in the Virginia horticulture area on the Northern Adelaide Plains between September 2007 and April 2008. Leaf mines on both Rhagodia species were caused by an endemic leafminer species, putatively Phytoliriomyza praecellens Spencer (Diptera: Agromyzidae). Ten species of parasitoids (all Hymenoptera) emerged from R. candolleana mines and seven different species from R. parabolica mines, mainly from the family Eulophidae and with some Pteromalidae and Braconidae. Trigonogastrella Girault sp. (Pteromalidae), Zagrammosoma latilineatum Ubaidillah and Hemiptarsenus varicornis Girault (both Eulophidae) were the most abundant species on R. candolleana , whereas two Opius Wesmael spp. (Braconidae) were the most abundant species on R. parabolica . Findings from this survey suggest an opportunity to plant purpose-designed refuges that could play a role in conservation biological control as part of an Integrated Pest Management strategy developed prior to incursion of pest leafminers such as Liriomyza species.