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
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
 Dead, dying parrotbush with healthy golden dryandra |  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!
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!
 Infested golden dryandra |  Early,mid stage larvae (instars) |  Empty pupal cases |
 Intact and broken pupal cases |  Fringed pupal cases |  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.
 Dead flower and surrounding leaves |  Caterpillar in hollow stem |  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.
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.
 2009 marri killed by fire |  2011 regrowth |  2016 healthy Banksia grandis |  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.