There have been many comments recently about widespread shrub death in Foxes Lair due to the exceptionally dry spring and summer.
Certainly, there is more death than usual, but this doesn't explain the scattered pattern in Foxes Lair with dead plants next to healthy ones.
Luckily my esteemed colleague Detective Doug volunteered to investigate this problem.
The great man randomly selected two each of dead and healthy Dilwynnia laxiflora (pea flower) plants for examination
The roots were very bent and thickened, particularly the tap root that snaps easily. Borer channels were on both the outside and inside, including one that contained a jewel beetle emerging from its pupal case.
No, being a true scientist, Detective Doug insisted on also examining the healthy specimens
Roots of both live plants had also been attacked, although to a lesser extent than dead plants.
The first plant had a few minor lesions but otherwise appeared normal. However when split in half lengthwise the root was hollowed out and contained a hibernating? jewell beetle. These beetles are common on pea flowers in October so presumably they hibernate until spring.
These plants are routinely attacked by borers and may survive for more than a year until invading canker fungus kills them or they snap off. Increased water stress from extended dry weather hastens plant death.
Interestingly, a previous investigation on wandoo crown decline in Foxes Lair found a similar combination of factors.