Ambrosia Beetles

Ambrosia Beetles—The True Nutritional Symbiont

By: Katy Newcomb

Ambrosia Beetles play an important role in nutrient cycling, yet many people view them as structural pests to an array of broadleaved trees and conifers.

Damage to the host is done primarily by the adult, who is reddish-brown to black, and less than half an inch long. The adults first locate a host, typically a freshly cut log, a windblown tree, or a tree that is severely stressed. They bore into the wood and produce small dust-like wood chips which are swept out of the tunnel. The beetles then proceed to excavate a series of tunnels throughout the wood. The handiwork of the ambrosia beetle is reflected by a black, curvy stain, indicating the path of the little critter. The beetles do not eat any of the woody material, but they find another way to obtain their nutrition. They provide nutrition for themselves by feeding on a fungus that grows inside of the tunnels. The “ambrosia fungus” originates from small spores that are located on the beetle itself, inside a small pocket within their exoskeleton. Ambrosia beetles lay their eggs, and fungal spores are inserted inside the tunnel. As the eggs mature and develop into ! larvae, they receive nourishment from the fungus. The fungi also provide optimal nourishment for adult ambrosia beetles. In addition to nourishment, the ambrosia fungi help prevent the intrusion of various pathogenic fungi. The ambrosia beetles in turn assist the fungi by providing them with excrement and plant remains, which serve as a food source.

The type of relationship that exists between the ambrosia beetle and this fungus is known as a type of nutritional, mutualistic symbiosis. They coexist with one another and they have been proven to be necessary for the survival of both organisms.

The ambrosia beetle is a very important species to nutrient cycling. They have a unique lifestyle and are greatly admired for their economic significance. Even though they are often seen as a pest, their damage is minimal. If they consistently present a problem, there are several ways to prevent their damage. Since they feed primarily on cut logs, the availability of lumber should be minimized. The beetles are attracted to the moisture of these freshly cut logs, so they should be processed immediately.