Friday, February 17, 2012

Twig Dieback in Podocarpus Trees

The black twigborer (Xylosandrus compactus) is a beetle that attacks over 200 plant species including orchids, citrus, avocados, mango, coffee, eucalyptus, hibiscus and podocarpus. The females tunnel into woody twigs, leaving pin-sized entry holes. Once inside, they excavate galleries and lay eggs.  It is this excavation that causes the damage to the tree. An infestation by one to three females is sufficient to kill the twig or branch. A severe infestation can kill a plant, including large trees. The damage is not caused by feeding, since the beetle larvae feed on a fungus that is introduced by the female beetle.
 Typical symptoms of black twigborer are wilting and death of leaves and wood beyond the beetle's entry hole. The dried, brown leaves frequently stay attached to the tree.

                                                    Entry hole

Cultural control
The best control is to maintain a vigorously growing tree. This will help the tree to resist beetle infestations and recover quickly from existing ones.  Prune and destroy all beetle-infested plant material.