The eucalyptus is a versatile landscaping plant that can be used for applications from decoration to windbreaks and fast-growing, renewable lumber. As with other types of trees, pests can be devastating to a group of eucalyptus trees. There are a handful of pests that are commonly found eating the trees, and early identification can mean saving a stand of eucalyptus.
The eucalyptus leafroller is an appropriately named caterpillar, for the only thing that this pest feeds on is the leaves, buds, shoots and flowers of the eucalyptus. The damage done by these insects is distinctive; the caterpillar doesn't chew through the whole leaf, but instead strips off the surface. This results in the browning of leaves, branches and flowers, which then eventually take on a skeletal look with the loss of everything but the veins. These veins will also shrivel and die.
The caterpillars excrete silk threads, which they use to bind the leaves tightly together to form shelters. Eggs are laid on the underside of the leaves, and hatch within about a week of being laid. When unchecked, an infestation of leafroller caterpillars can kill young trees and cause significant damage to older ones. Caterpillars go through several stages, during which time they have a variety of appearances from translucent to bright pink. After molting several times, they turn into moths.
Eucalyptus Longhorned Borers
Eucalyptus longhorned borers are beetles that will eat the wood of the eucalyptus trees, especially if the tree has been damaged by weather, stress or disease. Trees that have open wounds such as those from the loss of a limb are susceptible to these beetles, and those that do not have enough water are also vulnerable.
There are several different species of eucalyptus longhorned borers, but the damage they leave is similar. There will be holes in the bark where they have chewed through the wood, and this will eventually compromise the strength of the tree and lead to leaf loss and wilt. Pesticides and insecticides have been effective in getting rid of these insects, but it is generally easier to prevent the stress and disease that attracts the beetles in the first place.
Eucalyptus Leaf Beetle
The eucalyptus leaf beetle is one of the later species of beetle introduced to areas like the United States from their native Australia. These beetles feed on both the eucalyptus and on the blue gum trees and can be gray or brown as adults and greenish-gray as young beetles. Eggs are laid on the youngest leaves of the tree, and when the larvae hatch, they immediately begin to feed on these new leaves. Once the beetles get older, they will begin to feed on the older leaves of the tree. The damage caused can resemble that which is done by caterpillars, and will include leaves with the meaty parts chewed completely down until there is little left but the veins.
There are two different species of psyllid that feed mainly on the eucalyptus. The red gum lerp psyllid and the eucalyptus psyllid have become problems outside of their native Australia and have followed the eucalyptus that has been exported out of the country. They are more prevalent during seasons when the soil stays consistently moist and is not allowed to dry out. In warmer climates, their life cycle means that they will be most troublesome during the fall and winter when they will feed on the leaves of the trees. These insects will excrete a white substance on the leaves as they feed on them, and these small white dots are one of the easiest ways to distinguish a psyllid infestation.