In the Spring time last year this site posted an article on the damage to Wattles that Fireblight Beetle can cause, where thick regrowth of Black Wattle had been completely defoliated by these beetles and their larvae.
Over Summer the Fireblight Beetles have gone to ground and the Wattles have staged a dramatic comeback, with virtually all the wattles that looked dead and gone re-sprouting with fresh new growth along with new seeds germinating. Surely there will be another dramatic change later in the year in the cooler months when the Beetles become active and the Black Wattles will cop another attack. The whole process of the Wattles losing their foliage in spring would benefit other native plants that are fighting for space and light.
Recently a fairly dramatic change to the understorey has been occurring in some areas affected by the 2009 Bushfires. In some localities where the fires triggered mass germination of either Black Wattle (Acacia mearnsii) or Silver Wattle (Acacia dealbata) widespread defoliation and dieback of these species has become very apparent.
The cause of this dieback is an insect known as the Fireblight Beetle (Peltoschema orphana ). The Beetles lay eggs on the underside of the leaves and the small grub like larvae also feed on the foliage. The species (although native to Australia) has been identified as a significant pest when people have tried to establish Wattle plantations and the thick regrowth after fires of the wattles has mimicked these conditions.
The dieback has resulted in a rapid opening up of the understorey and more light and less competition will enable other species to grow. Look out for weeds taking advantage of this new open space, but hopefully the event can provide an opportunity for other native understorey species to flourish, while retaining enough Black and Silver Wattle trees to continue to provide important habitat for animals such as sugar gliders and various bird species.
The Beetle is thought to avoid summer heat by hibernating in spring. It emerges in Autumn to start eating new foliage and lay its eggs. The hatched larvae then form into new beetles and the cycle continues.