12. Predator prey associations

The gum leaf skeletoniser is a moth whose larvae defoliated more than
40 000 hectares of river red gum forest in the Murray and Goulburn Valleys in 1975. The 1975 outbreak followed earlier ones at intervals every ten years since they were forest recorded in 1933.

The moths are poor fliers so eggs are laid on low foliage. The eggs are grouped in masses called egg rafts. The young feed on the leaf's photosynthetic tissue, leaving the veins and midrib as a skeleton. The mature larvae spin a cocoon at the base of the tree in leaf litter. Moths emerge and live for about ten days. When the larvae moult, the old head skin remains, forming a hat.

The main predator is a fungus, Aspergillus, which controls the population. The fungus thrives in humid conditions following flooding. If flooding does not occur at a time when larvae are close to the ground, between March and June and October and January, the population will not be controlled. This greatly increases the potential of a population explosion of the next generation. There are two generations each year. Based on Defoliation of River Red Gums by Gum Leaf Skeletoniser, 1986, Research and Development Note, Dept. Conservation, Forests and Lands vic.

Foxes and feral cats are important predators in river red gum forests. The following mammals were identified in fox and cat scats in a study of Barmah Forest (river red gum): sugar gliders, yellow-footed antechinus, ringtail and brushtailed possums. Local residents also reported that bandicoots, stick-nest rats and bettongs were once present. The decline in mammals appears to have coincided with European settlement and consequent loss of habitat from grazing and the introduction of foxes and cats.

adaptations	allelopathy