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Inside Eucalyptus caesia

13/7/2022

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Picture30+ Carnabys cockatoos on my E. caesia
Greetings fellow foxies,
About 33 years ago I planted a Eucalyptus caesia subspecies caesia (gungurru) mallee in my front yard, which has grown into a magnificent specimen that produces cascades of beautiful pink flowers. It is great bird attractant, particularly New Holland honeyeaters and western wattle birds, which claim ownership at various times of the year. Lately most flowers (and my wife's roses and geraniums) are lopped by ### twenty eight parrots. Very occasionally red-tailed black and Carnabys cockatoos chew the nuts, but not red capped parrots. Plenty of honeybees.
Eucalyptus caesia is a rare bird-pollinated species that is endemic to 25 granite outcrops in the Central Wheatbelt of Western Australia, but is widely grown in native gardens. Every surviving flower on my caesia develops into a nut even though the nearest other caesia is over 200 metres down the road, and I see the same with single eucalypt species in Foxes Lair. Evidently most eucalypts can self pollinate!

PictureLignotuber on my 33 year old E.caesia
This study of E. caesia pollination at Boyagin Rock revealed some amazing information.
  • The large flowers are mainly pollinated by birds, which regularly  transmit pollen up to 120 metres.
  • On average there were three genetic groups at each mallee patch, which minimised damaging inbreeding. Insect-pollinated plants would have less diversity
  • Clumps often had a group of clone plants which developed into individual plants as the lignotuber (mallee root) expanded then rotted between suckers. The largest  clonal patch comprised 55 stems over an area 8.8 m wide and 11.5 m long. This patch may be thousands of years old and among the oldest known eucalypts. I was impressed by the 80cm diameter root on my 33 year old plant before reading the paper.
  • At natural Caesia locations, there hasn't been a surviving seedling for over 50 years. Fire is required to remove competition.
  • The paper provides an opportunity to revise your knowledge of statistics and  words like cleistogamy and kurtosis.

I collected flowers at varying stages of development for examination. Pollen develops early in the flower's development, and is actively collected by honeybees as soon as the bud cap is shed, and inward-facing stamens still formed a tube down to the flower base. Soon afterwards bees crawled down into the base where nectar was being produced. Honeyeaters also started feeding as the stamens folded out and fully opened.
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​ Bees vigourously wiggled their way across stamens, stuffing pollen into their leg-sacs.The anthers seemed to be sticky and didn't spontaneously shed pollen like most other flowers.
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Bee harvesting pollen
I noticed bees still licking nectar from the flower base in mature flowers while anthers were declining. This indicated that the later maturing stigma on the end of the style was still receptive to pollen. It is a logical way to prevent the flower pollinating itself.
Signs of stigma maturity were subtle, but images show it changes from being hidden in the bud cap,then a fold at the tip (non-receptive), to a moist receptive bulge.
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Stigma hidden in bud cap
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Stigma in groove, non receptive
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Stigma raised, receptive
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Flower has finished
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​Honeybees are larger than most native bees, but it was evident that they rarely contacted the stigma due to large flower size. They just stole pollen and nectar while birds, small animals, (large flower wasps?) did the pollination.
Apart from stink bugs, which routinely remove growing points from most seedlings I try to rear in Foxes Lair, few insects bother my street tree. This little fellow is tolerated.

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Parrotbush Decline in Foxes Lair

21/1/2021

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​Hello fellow Foxies,
About three years ago during a very dry spring I noticed that parrotbush (Banksia sessilis) plants on Banksia Walk shallow ironstone soil east of the water tank were severely infested with a scale insect. The damage has progressed each year to the extent that most plants there are dead or unthrifty. Accompanying golden dryandra (Banksia nobilis) plants are much less affected
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Dead, dying parrotbush with healthy golden dryandra
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Severely damaged parrot bush plants
​After much investigation I discovered that symptom severity is linked to soil water holding capacity, with far less damage on deeper and sandier soils. Another finding was that two organisms are involved. The first was identified as whitefly, but a new species rather than the common Aleurotrachelus dryandrae
Adult whiteflies look like tiny white powdery moths, but I am yet to see any. The mains signs are small powdery spots (early larvae), yellowish to brown scale-like mid-stage larvae and pupal cases that look like miniscule white crystal coffins. Whitefly are supposed to only be on the leaf underside, but this species is often on the upper side. Infested leaves often have a powdery or waxy looking coating and black spots that may be associated with honeydew exuded by the larva. The spots look like insect poo to me!
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Infested golden dryandra
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Early,mid stage larvae (instars)
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Empty pupal cases
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Intact and broken pupal cases
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Fringed pupal cases
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Varying levels of damage
​While the leaves are being sucked dry, the growing points are also being killed by an evil caterpillar. From an egg laid on shoot or flower, the caterpillar hollows out the stem to the first node. It returns to the dead growing point to pupate and exit.
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Dead flower and surrounding leaves
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Caterpillar in hollow stem
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Hollowed out stem and flower
​Moisture stressed plants are more susceptible to diseases and pests, and increased temperatures also increase temperatures worsen pest damage by speeding up their life cycle.
The Banksia walk was named after a small group of Bull Banksia (Banksia grandis) plants that occur on this soil. They have been struggling in recent years, and some are dying this summer. Interestingly they are not greatly infested with whiteflies or borers. This area is a photo-reference site that I have been monitoring. Images changes since the 2009 fire.
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2009 marri killed by fire
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2011 regrowth
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2016 healthy Banksia grandis
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2021 Banksia grandis dying back
​This is another biodiversity loss in Foxes Lair in addition to flooded gum death, marri decline, and wandoo crown decline that I have observed in the last 20 years.  I still remember being surprised when I arrived in Narrogin in 1986 and a farmer told me how much his farm’s rainfall had fallen. We now have even less and more variable winter rainfall. 
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Lightning Tree

30/9/2020

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PictureTree amongst granite rocks

​Greetings fellow Foxies,
I am constantly reminded to avoid sheltering under trees in a storm. Most reminders are large branches and trees I find that are falling now at a much faster rate than they are being replaced. I wonder whether this is due to trees being less protected in isolated reserves, stronger winds or lower subsoil moisture. Either way, bird and wildlife habitats are being lost and a day will come when we will have to replace them to avoid dramatic local species loss.
Another reason became clear as I was exploring a granite outcrop in Borgey Block. I came upon large, jagged slabs of fresh wandoo trunk scattered through the rocks that surrounded a destroyed mature wandoo. A lightning strike had completely split the tree and blown stem pieces and branches around a twenty-metre radius. The tree had literally exploded with the trunk split down to ground level.
Surprisingly, it was still (barely) alive.
A friend who was did insurance assessments made this interesting comment "​I have high respect for lightning;  seen many trees split asunder and of course many insurance claim inspections on livestock victims.  
Always fascinates me how different tree species carry a lightning charge.  Most Wandoos literally blow up and scatter everywhere, red gums carry similar damage but sometimes just shatter in the upper trunk, Jarrah carries the charge down the outside of the trunk like a chisel groove and York gums often just pop off branches or top trunk.  I don’t think I have ever seen a lightning strike on a salmon gum even though they are often the tallest, single tree in the neighbourhood"

This fascinating article shows that lightning can have a range of effects on a tree

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Jagged pieces of trunk strewn amongst rocks
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This side of the wandoo has exploded
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Branches have been blown away
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Split to ground but resprouting
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Balga bugs

17/3/2020

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PictureGiant balga at Candy Block
The balga Xanthorrhoea preissii, a grass tree, is a striking part of our bush that was use by Noongars for medicine, tools and sustenance. Grass trees are monocotyledons but neither grasses nor trees.
 Carbon dating has found grass tree ages of up to 1,000 years. Also, they have special contractile roots that pull seedlings underground so that plants on sandy soils may not develop an above ground stem for 10 to 30 years. I reckon that the five-metre plant I found in Candy Block must be ancient. Unfortunately, twenty-eight parrots are now attacking its new growth.
 
The grass tree at Foxes Lair is the smaller Xanthorrhoea brevistyla that lacks an above ground trunk. It is an insect magnet when flowering in November.
 
I regularly see severe insect attack on balga flowering spikes and brought one home for examination. The green stem had frequent reddish- brown sunken lesions with gum exuding from small holes. The split stem revealed tunnels containing bardi grubs, surrounded by reddish brown fungal infection. Once again, a canker fungus that affects eucalypts and other shrubs

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Bardi grubs inside fungus infected galleries
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Sunken brown lesions and gum exuding from borer holes
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Interestingly, a previous investigation on wandoo crown decline in Foxes Lair  found a similar combination of insects and fungus. The fungus causes severe damage to trees and shrubs. Fungus doesn’t seem to affect the balga trunk, presumably because flowering spikes naturally die before it can spread further.
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​The bardi grubs are larvae of longicorn and cockchafer beetles. They have tunnelled up through the entire flowering stem.
The flowers and seeds were attacked by a brownish caterpillar that eats them under a protective cover it makes from its frass (poo) and silk.

​Last year I received a shock when one of two apparently healthy balgas that I had photographed earlier snapped off at mid stem
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Before
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After
​The centre of a normal trunk is filled with living fibrous material above a woody cone-shaped base that remains long after a plant has died. The living centre is surrounded by old leaf bases held together by natural resin, which provides support and excellent fire protection.
The fibrous centre of the dead balga was completely replaced by a soil-like material containing wireworms, which were attacking the interior of the surrounding leaf bases
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wireworms in rotted grass tree centre
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surrounding leaf bases being eaten
​As Noongars ate bardi grubs that were in the centre of dead balgas, I suspect that they had chewed out the living material before wireworms moved in.
This balga had been surviving with a decayed centre for some time until the weakened stem snapped. It is a natural process and dead remnants can be attractive in their own right.
 
Unfortunately, increased in Australian ringneck parrot (twenty eight) numbers are causing premature balga death from them continuously chewing the new growth.
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Balga killed by grubs
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Balga being killed by twenty eight parrots
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    Doug Sawkins is a friend of Foxes Lair 

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