Origin:
These two beetles are native to Australia, but were discovered in California in 1998 and 2003.
Biology:
This beetle is one of two species that have recently found their way into California from Australia, and which feed on the many species of exotic eucalyptus trees in that state. The beetles feed on the foliage, causing notched leaves and in heavy infestations may leave only the mid-vein of the leaf behind, resulting in near defoliation of the tree. This in turn stresses these trees and could lead to their death. Female beetles deposit up to 40 eggs on the leaves or under crevices on the bark. Both larvae and adults feed primarily at night, hiding under loose bark much of the day. Development from egg to adult can be about 5 weeks, and there may be 3 generations per year.
Identification:
Adult beetles of both species are similar, with an oval, rounded shape dorsally and a very flattened ventral side, giving rise to their common name of “tortoise” beetles. The adults are less than 3/8 inch long and have a coppery color to their dorsal side with varying degrees of black spotting and banding. The larvae somewhat resemble small, dark caterpillars but can be distinguished by the lack of prolegs along the abdomen. Their color is dark green to reddish brown and with the head and first segment of the thorax black.
Characteristicts Important to Control:
Low populations of these beetles will not cause harm to healthy trees, and chemical applications may not be warranted. Good tree health is important in preventing stress on the tree. If beetle populations are high chemical applications may be needed, and on small varieties of eucalyptus foliar applications of a contact insecticide will help, including treatment to the bark where the insects hide. Systemic applications to the soil may be more appropriate for larger trees, but should be made well before the beetle numbers are too high. Efforts are being made to find parasitic insects that can control the beetles in the egg or larval stages.
