Weeping Eucalyptus Trees: Why Is My Eucalyptus Tree Leaking Sap

Weeping Eucalyptus Tree Leaking Sap
eucalyptus sap
(Image credit: THPStock)

A eucalyptus tree dripping sap is not a happy plant. The condition often indicates that the eucalyptus tree is under attack from a type of insect called the eucalyptus borer. A eucalyptus tree oozing sap onto limbs, or the trunk is very likely a tree attacked by a long-horned borer insect. Very few options exist for assisting the tree once it is attacked. Since often it is stressed trees that are infested, the best defense is to provide adequate irrigation and use good cultural practices. Read on for more information about the causes of eucalyptus tree oozing.

Why is My Eucalyptus Tree Leaking Sap?

The first time you see a eucalyptus tree dripping sap, you may think it looks like it is weeping or bleeding. In fact, the fluid you see coming from holes in the weeping eucalyptus is the attempt of the eucalyptus to kill and wash out boring insects. Several species of long-horned borer beetles can damage eucalyptus trees. They are attracted to trees suffering from water stress, as well as freshly cut eucalyptus wood. These beetles have antennae as long as or longer than their bodies. Female beetles lay up to 300 eggs beneath loose bark on stressed trees. The eggs hatch in a few weeks and bore into the inner bark of the tree. The larvae dig out long galleries, then pack them with frass excrement and wood shavings. After several months, the larvae pupate and emerge as adults to repeat the cycle. The eucalyptus tree responds to the wounds by flooding the holes with a chemical called “kino,” or sap, to trap and kill the bugs. That is when a gardener begins to ask, “Why is my eucalyptus leaking sap?”. Unfortunately, the tree is not always successful in repelling insects.

Leaking of Eucalyptus Trees

When you see weeping eucalyptus, the tree is already infested with the larvae. At this stage, no pesticides are very effective in helping the tree, since the larvae are already inside the wood. The best way to help a eucalyptus tree avoid a borer attack is to provide it with sufficient irrigation. The specific amount of water required by a tree depends on the planting site and the species. Generally, it is a good idea to irrigate your eucalyptus tree infrequently but generously. Once a month, provide enough water to penetrate a foot (30.5 cm.) or more below the surface. Use drip emitters for several days to allow the water to seep into the soil. In order to prevent weeping eucalyptus, it also pays to choose the species you plant carefully. Some species and cultivars are more resistant to these pests and to drought. On the other hand, eucalyptus species that come from the wetter regions of Australia fare particularly badly in a prolonged drought. They are especially susceptible to being attacked and killed by borers.

Teo Spengler

Teo Spengler has been gardening for 30 years. She is a docent at the San Francisco Botanical Garden. Her passion is trees, 250 of which she has planted on her land in France.