Extracts from Newsletter Issue no 253 March-April 2004


General Meeting Report
:
 March 15 
Judy King gave an excellent talk on the introduced Sirex wasp, Sirex noctilio, supported by computer-driven illustrations and annotations. Females don't sting, but have a huge saw-like ovipositor, orange legs, and are quite large, up to 6 cm long (including antennae). Males are orange on the back and abdomen, with black legs and wings.  The larvae feed on a fungus growing through timber, Amyleostereum areolatum. 

   Females introduce the food fungus into the tree when they lay there.  They drill holes into the bark, firstly to inject the fungal spores and a phytotoxic mucus.  Stressed, damaged, or otherwise unhealthy trees are targeted and if the female is satisfied the tree is sufficiently unhealthy, she will then drill another hole and deposit up to 400 eggs.  The holes can be seen as pin holes; beads of resin show where they are.  The mucus dries off the tree, the fungus causes a brown tea staining as it grows and slowly kills it, from the bottom up.  The needles go brown, the whole tree goes a coppery brown colour. 

   The larvae tunnel through the fungal-infested wood, pupate just under the bark.  Tunnels go in all directions and ruin the wood. The larva is white and has a spine on its end.  Adults cut an oval emergence hole, 3-6mm in diameter.  The life cycle is usually 1 year but can take up to 3 years.  Adults are present from October to early May.  They live a few weeks and can fly up to 50 km.

  The wasp is native to the Mediterranean region of southern Europe from Spain to Turkey.  It now occurs in South America, New Zealand, the tip of South Africa and southern Australia.  Within 28-30 years of its appearance in New Zealand  it had devastated NZ softwood plantations.      

   In its native area it is not a problem, but it has found its new host, Pinus radiata, to be very much to its liking.  The pine plantations of Australia had few pests until the advent of this wasp.  It was found in Tasmania in 1950-51 near Hobart, and in the years 1952-59 killed 40% of the trees in an 1100 ha plantation.  It arrived on the mainland, at Melbourne, in 1961 and an eradication program was started, to be carried on until 1972 when it was abandoned and a biological control program was begun.  This aimed at minimising damage, as eradication was not possible.  The controls used are nematodes and parasitic wasps, as well as the removal of stressed or unhealthy trees.  Then in the 1980s there was a huge outbreak in South Australia.

  Robin Bedding, of CSIRO, studied the life cycle of the nematode and worked out how to manipulate it to control the wasp.  The nematode has two parts to its life cycle: a free-living cycle when it feeds on the Amylosterium fungus, and a parasitic cycle where the female feeds on the wasp larva.  

  In a somewhat complicated process, the nematodes sterilise the female wasps so that they lay sacs of nematodes instead of fertile wasp eggs, thus increasing the nematode population.  The process is further assisted by the injection of nematode larvae into trees affected by the fungus when they under 5 days old as it is then that they become infective.  To do this, personnel use a special hammer with a small sharp point to make a hole in suspect trees and inject (with a sauce bottle) liquid contained the nematodes.

  Of the parasitic wasps introduced, only two have been successful, Ibalia leucospides, which targets eggs and very small larvae; and Megarhyssa nortoni, which parasitises older larvae; thus covering a wide scope.

  Sirex has reached Tenterfield and is expected to arrive in Queensland soon.  It is likely that it will adapt to the warmer climate here, as it has done so in South America.  The question remains as to whether it will affect the other Pinus species that are mainly grown here.




Excursion Report:  Enoggera Army Reserve, March 21.

Thirty-four members and friends arrived at the gates of the Gallipoli Barracks. A list of people and cars was presented to the gatehouse and we drove in convoy to the barracks reservoir.

   The weather was very pleasant. It was warm, overcast and with a breeze. Our walk took us across the reservoir embankment, then uphill along 4wd tracks towards Enoggera Hill.  The bush thinned out and the canopy was higher as we moved away from the reservoir.

   The breeze did not help birding. Twenty-four species were sighted, the highlight being three Wedge-tailed Eagles, two large and one smaller, which patrolled low over us for some minutes. The three birds were quite dark and may have been old.

   Weeds were more obvious on foot than on the 4wd reconnaissance. Molasses grass was widespread and flowering. In all 20 grasses were identified, with 10 introduced species.  The poisonous Rosary Bean, Abrus precatorius, with its ricin load was common and caused some discussion.

   Copies of the keys for the eucalypts of Brisbane had been distributed and many used them to good effect. Recent winds had brought down branches and uprooted some trees. The fallen branches with attached gum nuts assisted in identifying the species in our area. Some excellent examples of Tallowood, E. microcorys, and E. major were close to our path. Brush box, Lophostemon confertus was common throughout; Forest Oak, Allocasuarina torulosa,common on the slopes.

   Members worked hard compiling lists of plant species (including ferns and grasses), birds and butterflies.  There were 118 species of plants, with 28 weed species and 5 spreading native plants.  One of interest was a small vine, Aristolochia sp. ‘D’Aguilar’, not only for itself but also because there was a final instar larva of the Big Greasy butterfly, Cressida cressida, feeding on it, having almost exhausted its supply of this hostplant and with no others in sight.  Another interesting plant was Pultenaea spinosa, more often found further north.

   Several larvae and pupae of the Common Imperial Hairstreak butterfly were found on a Black Wattle, Acacia leiocalyx, with many ants of the genus Iridomyrmex in attendance. Only three common species of skippers (Hesperiidae) were seen, in spite of good conditions for grass, matrush and sedge growth, their main hostplants.  However, 37 species of butterflies were identified on the day.

   Our thanks to the Enoggera Army Unit for permission to visit their reserve.

                                                                        David Shaw




No. 789          Mystery frog

In the handy guide, Wildlife of Greater Brisbane, Greg Czechura, the author of the frog section, mentions that Litoria brevipalmata, the Green-thighed Frog is a >mysterious= frog that suddenly erupts in large numbers only to disappear quickly again.  I personally had only seen one specimen on two separate occasions over the last 15 years.  Recently, however, while with a group surveying the fauna of a new National Park near Ravensbourne, I had the good fortune to observe at least 5 pairs mating in a small ephemeral pond in a gully in the forest and the following night five patches of spawn were seen.  Small black eggs were suspended in a clear jelly-like substance, which floated just under the surface.  Each oval patch of eggs was 130-150mm by 80-100mm in size. 


   The adults had gone!  Nobody knows where they spend the 112 months each year between the short breeding periods; however, I have heard many theories, from up in trees, in tall grasses and sedges away from water, to under thick leaf litter in the forest.  Personally I have raked litter in forests looking for small snakes and skinks over the past 16 years and have yet to turn up a Green-thighed Frog.  Still, I live in hope as we need to work out this mystery if we hope to save this very attractive frog.  If any member can add to this information I would like to hear from them via a nature note.                                         Ray Leggett