Common names: Ambrosia Beetle, Asian Ambrosia Beetle
Scientific name: Order Coleoptera, family Scolytidae, Xylosandrus crassiusculus
Identification: Females excavate galleries in stems or trunks and push out plant material, which sticks together and forms narrow protrusions that look like toothpicks. These protrusions are usually the first show of an infestation. One plant can have many such protrusions.
Biology and life cycle: Larvae bore horizontally into tree trunks. They remain in the tunnels until mature; after they mate, the females leave the host plant. Males are flightless and die in the host plant. A generation may be completed as fast as twenty days or take up to four months. Usually one generation per year. Complete metamorphosis.
Habitat: Tree and tropical plant trunks. Host plants include over 120 known plants, including pecan, Chinese pistachio, red oak, bur oak, redbud, Bradford pear, and chinkapin oak.
Feeding habits: Females bore into plant trunks and inoculate the tunnel with fungal spores. Then the females produce a brood. The larvae and the females feed on the developing fungus rather than the host plant.
Economic importance: Heavily infested plants usually die from the inoculated fungus or a secondary disease.
Natural control: No predators discovered yet.
Organic control: Keep trees healthy and compost infested wood at earliest detection. You can also cut down the infested tree and let it rot, or soak the trunk with plant oil spray or orange oil.
Insight: For now, this pest is mostly located in East Texas.
Ambrosia beetle is a generic for a number of genera of insects. The ambrosia beetle may cause significant damage to green logs and unseasoned lumber, and occasionally to dead, dying, or stressed trees.
As the insect chews through the bark and into the wood, it create a gallery of winding tunnels . It does not use the xylem as food, but uses the galleries as a place for a fungus to grow. The fungus becomes the food. Because of this dependence on the fungus,
Boring dust at base of tree
Photo credit: USDA Forest Service
The insect carries spores of the fungus with it as it moves to other trees guaranteeing a food supply.
Wood debris from the galleries appears as fine sawdust and is pushed out of the galleries where it accumulates around the entrance hole and at the base of the tree. This insect can only survive in very weakened or dying trees, or in wood products that have not been properly dried. Moisture is needed to allow the fungus to grow.
Control is the Sick Tree Treatment to get the trees healthy and applying orange oil or hydrogen peroxide treatments to infested trees
For more information about this and other insects, get Howard Garrett and Malcolm Beck’s book – Texas Bug Book – the Good, the Bad and the Ugly.