Literature review: Impact of Chilean needle grass ... - Weeds Australia

was once widespread in south- eastern Australia but in 1993 there were only three known populations recorded since 1950, one
in the ACT and two in Victoria (Edwards 1994). Edwards (1994) investigated eight additional likely sites in Canberra and one in
NSW and found populations at all except one in central Canberra. Recent surveys have found it at 43 sites in NSW and 12 in the
ACT (Endersby and Koehler 2006). The South Australian distribution is based on a single individual from Bordertown (Edwards
1994) and it has not been found recently in that State (O’Dwyer 2004). Endersby and Koehler (2006 citing C. O’Dwyer pers.
comm.) stated that: “Prior to 2003, the species had been reported from just six areas in Victoria – Broadford, Tallarook,
Flowerdale, Dunkeld, Hamilton and near Nhill-Salisbury”. However that is a highly misleading statement that should have been
qualified, perhaps as ‘probably extant populations’. Edwards’ (1994 pp. 32-33) map and list of historical records showed many
more localities with much wider distribution. The map provided by O’Dwyer(1999) apparently leaves out historical records
noted by Edwards (1994) including Ararat, Bendigo, Castlemaine, Gisbourne, Maryborough, Monbulk, Nagambie and Woodend.
The map provided by O’Dwyer (2004) is more complete, showing c. 24 distribution localities prior to 1970 and c. 7 sites after
that time. Gilmore et al. (2008) stated that there were only four records in the Melbourne area prior to 2003, near Keilor,
Broadmeadows and Laverton. Recent records in Victoria include grasslands in the Deer Park, Craigieburn and Epping areas
(Endersby and Koehler 2006, Gilmore et al. 2008), at Greenvale and Woodlands Historic Park (personal observations, Gilmore
et al. 2008) and Moyhu (personal observations).
Edwards (1994) considered S. plana to be restricted to Austrodanthonia patches in native grasslands, mostly on low hills or rises,
sometimes in grazed and mown areas. He stated (p.34): “The foodplant is known to be Danthonia”. Driscoll (1994) stated that
the moth requires Austrodanthonia carphoides and A. auriculata grassland for survival. According to O’Dwyer (1999) and
O’Dwyer and Attiwill (1999) S. plana inhabits native grasslands and grassy woodlands with >40% Austrodanthonia cover with
some sites having up to 75% cover, on soils ranging from sands, through loams to clays, with available P below 14μg/g.
O’Dwyer (2004) states that its habitat is native grasslands dominated by Austrodanthonia spp. particularly including also A.
eriantha and A. setacea. She noted that oviposition by S. plana has not been observed. At Craigieburn and Epping, Victoria, it
has recently been found in habitat previously considered atypical, dominated by T. triandra (Endersby and Koehler 2006).
The flight period of S. plana is variable from place to place and year to year (Driscoll 1994), possibly late October peaking in
mid November and early December and through to at least the end of January in ACT (Edwards 1994), mainly 11 am – 2 pm
(Edwards 1994). According to Driscoll (1994) the likely duration of the larval stage is 21-22 months. O’Dwyer (2004 p. 3)
suggests “about 11 months”. Edwards (1994) mentioned the absence of parasite records, and recorded some bird predators of
adults. O’Dwyer (2004) mentioned Willie Wagtail Rhipidura leucophrys and robber fly (Asilidae) predation of adults.
Much of the literature on S. plana repeats unproved suppositions or speculation as facts, usually including Austrodanthonia spp.
being food plants and native grassland habitat specificity, and fails even to provide full lists of known sites of occurrence. A
large number of research projects on the species have failed to establish its most basic life history, including hosts plants and the
duration of the larval stage. The most recent information (e.g. Braby and Dunford 2006, Endersby and Koehler 2006, Gilmore et
al. 2008) indicate it is a widespread and common species that thrives in degraded pastures, including areas dominated by N.
neesiana. The development of knowledge of this species is instructive. It has never been, as claimed by New (2000) a species
“appraised reasonably fully” and its use as a flagship taxon has been of little value even for its own preservation, since so much
of its basic life cycle remains poorly understood.
S. selene has been considered a particularly significant taxon because it exists in five distinct parthenogenetic forms (Douglas
2000); however it has not been listed under Victoria’s Flora and Fauna Guarantee Act (Department of Sustainability and
Environment 2009a) (Table 18).
The Cryptic Sun Moth S. theresa Doubleday is morphologically similar to other Synemon species in the grass-feeding group and
it has been suggested that it too feeds on Austrodanthonia (Douglas 2003b). No existing populations are known but locality data
on old specimen labels indicate it was an inhabitant of open grassy woodland with Austrodanthonia and Austrostipa in the
understorey (Douglas 2003b). It is listed as a threatened species under the Victorian Flora and Fauna Guarantee Act
(Department of Sustainability and Environment 2009a).
The Orange Sun Moth S. nais Klug occurs in the Mallee in Victoria and in South Australia and Western Australia. In the Mallee
it is known from “a floristically diverse combination of open grassy areas interspersed with stands of trees and shrubs”, the
grassy areas dominated by Austrodanthonia setacea and Austrostipa spp. (Douglas 2003b p. 7). Oviposition behaviour suggests
that A. setacea and an unidentified Austrostipa sp. may be larval hosts (Douglas 2003b). It is listed as a threatened species under
the Victorian Flora and Fauna Guarantee Act (Department of Sustainability and Environment 2009a).
Only a single population of the Striated Sun Moth Synemon sp. aff. collecta is known in Victoria, from near Shelley. Its habitat
may have originally been open grassy woodland and grassland dominated by Austrodanthonia spp. (Douglas 2003b).
Edwards (1996) noted that the “grass feeding species in particular have sufferred drastic reductions in distribution from the use
of grasslands for agriculture”; urban development threatens populations of some species and invasion by introduced weeds has
been identified as a threat to S. plana: “Without grazing or mowing the low-growing natives can become shaded and eventually
choked out by taller exotic plants” (Edwards 1993 p. 17, Edwards 1994). In western Victoria this species survives in sheepgrazed
Austrodanthonia pastures in which fertilisers and pesticides are not used (Dear 1996). According to Douglas and Marriott
(2003 p. 90): “Any disturbance, through ploughing and other types of cultivation and/or excessive invasion of exotic grasses and
forbs” leads to the disappearance of Synemon spp. Exotic perennial and annual grasses, not including Nassella spp., are listed as
threats by O’Dwyer (2004). Cultivation in Two Wells area of South Australia was blamed for the extinction of S. selene in South
Australia (Douglas 2000). These opinions should be viewed with some scepticism since they are based almost solely on
observational correlations. S. plana continues to exist in areas of the ACT subject to light grazing or mowing, and the
underground larval stage probably confers resistance to fire (Driscoll 1994). Douglas (2000) suggested that moderate disturbance
from grazing, slashing or possibly fire appears to be necessary for S. selene to flourish (Douglas 2000). Douglas and Marriott
(2003) advocated weed control and regular mowing, burning or grazing to remove accumulated dead grass “that provides cover
for predators and reduces the extent of acceptable sites for oviposition”.
159