Eucalypt trees have become abundant in the California landscape, but so have the many invasive eucalypt pests that have arrived in California in the last couple decades.
In the fall of 2022, yet another invasive pest was added to the hoard of beetles, psyllids, and gall wasps that attack eucalypt trees. The dotted paropsine leaf beetle (Paraopsis atomaria) was found on a lemon scented gum tree (Corymbia citriodora) in Los Angeles County. It was the first report of the dotted paropsine leaf beetle in North America, and it has since become more problematic throughout Southern California. Currently the extent of the spread is unknown.
Like eucalypt trees, the dotted paropsine leaf beetle is native to Australia, where it is known as an abundant pest of at least twenty Eucalyptus and Corymbia species. Some of these tree species are commonly found in California, including the red gum (E. camaldulensis), rose gum (E. grandis), sugar gum (E. cladocalyx), and the silver-dollar gum (E. polyanthemos).
What does it look like?
Adult beetles are about 3/8 of an inch with oval bodies and little beady black eyes (Figure 1). They are tan in color and covered in orangish dots. There are darker spots along the top and edges of the wings. The antennae are straight and become slightly darker toward the tip.
Eggs are laid in a circular cluster around young stems and leaves. They are tan, cylindrical, and are laid in clusters of 20 – 100 eggs. The larvae of the dotted paropsine leaf beetle are yellowish in color with black heads and black ends (Figure 2). As they age, they develop black stripes along the top and sides. When larvae are threatened, they will raise their black back end. They will drop to the ground to pupate.
Damage and Solutions
Although small, the dotted paropsine leaf beetle and its larvae can cause significant damage to the leaves of a host tree. If they do not eat the whole leaf, they will leave behind distinct notches in the leaves like other eucalyptus leaf beetles. Severe infestations can cause defoliation and eventual death in stressed or young trees.
You can protect Eucalyptus or Corymbia species against insect infestations by providing proper horticultural care. Reducing any water or other environmental stressors will allow the tree to successfully fight off insect infestations.
If you are removing a eucalypt tree or dealing with a severe infestation, consider replanting with a California native or other tree that will not be susceptible to the dotted paropsine leaf beetle and other eucalypt pest.