You may have observed a decline in the crown health of wandoo trees recently. This is largely due to a reduction in rainfall and increasing temperatures causing the trees to become stressed and vulnerable to insect infestations and associated pathogenic fungi. Single paddock trees and road side trees are more likely to suffer from crown decline, possibly due to the fact there are less of the insects’ natural predators.
The beetle, known as Cisseis fascigera, can cause decline in wandoo crowns. The adult beetles lay their eggs on the bark of twigs in summer, the eggs hatch and the larvae bore a tunnel down the twig and branch, which results in branch death, particularly in autumn.
Lerp (psyllid) can affect stressed wandoo trees, they are sap sucking insects which attack leaves causing discolouration and defoliation. Eucalyptus rudis known locally as flooded gum, are also commonly affected by lerp especially in creek lines and river systems. Most trees can cope with high lerp numbers for a couple of seasons, climate is one of the main factors that influence the growth and decline of lerp populations.
Wandoo crown decline is more prevalent in dry autumns and most trees are able to recover from the associated insect infestations. An unintentional cause of tree decline can sometimes be caused by spray drift from herbicide applications.
If you would like more information see the links below:
Thanks to Peter White from DBCA for this information.