Ambrosia Beetle

“Some species of ambrosia beetle can fertilize eggs without a male.”

The ambrosia beetle is a loosely related group of weevils/beetles that form a symbiotic relationship with the ambrosia fungi. A symbiotic relationship benefits both parties. The ambrosia beetle can burrow through dead or dying trees.

Once it’s deep within the wood, they will then set up and cultivate a kind of fungal garden to feed their larvae. The beetles benefit by feeding directly on the cultivated fungus.

The fungus benefits by spreading into new habitats, even as it’s fed on by the beetle. This article will cover some interesting facts about the identification, diet, habitat, and life cycle of the ambrosia beetle.

Species, Types, and Scientific Names

The ambrosia beetle isn’t considered to be a specific taxonomical group, but rather a loose category that includes more than 3,000 species, spread across several different families, that feed on the ambrosia fungus.

Here are some of the most common species:

• Xyleborus glabratus
• Mountain pine beetle
• Xyleborus dispar
• Tomicus piniperda
• Austroplatypus incompertus
• Spruce wood engraver
• Scolytus schevyrewi
• Large Fruit Bark Beetle
• Hylastes ater
• Cryphalus piceae
• Hylastes cunicularius
• Xyleborus baculum
• Xyleborus africanus

Most species generally belong to the bark beetle family (Scolytinae) or the pinhole borer family (Platypodinae). Both families may have evolved independently from each other. Likewise, the ambrosia fungus isn’t a specific taxonomical group, but merely any species that are fed upon by the ambrosia beetle.

Evolution and Origins

Xleborus glabratus is believed to have been brought into the United States through solid wood packing materials, posing challenges in detecting these cryptic ambrosia beetles in tree or wood product shipments.

The ambrosia beetle belongs to the weevil subfamilies Scolytinae or Platypodinae and is characterized by its obligate association with nutritional fungal symbionts. This obligate symbiosis with fungi is observed in at least 11 separate groups of scolytine and platypodine beetles.

Coleopsis, an ancient beetle species, holds the distinction of being the oldest known beetle, having existed during the earliest Permian period approximately 295 million years ago in Germany. These early beetles, collectively referred to as “Protocoleoptera,” are believed to have been xylophagous, meaning they fed on wood, and had the ability to bore into wood.

Appearance

The ambrosia beetle has a small cylindrical body with reddish-brown or black colorations. Their sharp jaws enable them to see through the decaying wood with ease. Some of them have oddly shaped shells that almost look like full plates of armor extending over the head.

The larvae, by contrast, are white legless grubs. They look nothing like the adults. However, identification can be quite difficult from appearance alone, because there is an enormous amount of diversity in this group.

Habitat

The ambrosia beetle is found all over the world, but the highest concentration and greatest diversity of species probably occur in the tropics. They live anywhere with a sufficient number of trees. All species attack dead, dying, and stressed trees (rarely young nursery trees).

A few species from Asia also attack healthy trees, which can become a huge problem if they invade other regions of the globe. Both the granulate ambrosia beetles and the red bay ambrosia beetle may feed on healthy trees.

Diet

The ambrosia beetle can be described as a fungivore. This means it feeds exclusively on fungi.

What eats the ambrosia beetle?

The ambrosia beetle is preyed upon by several different birds, mammals, spiders, insects, and other small predators. The deep “nursery” inside of the tree offers a degree of protection against potential threats, but otherwise, they have few defenses.

What does the ambrosia beetle eat?

The diet of the ambrosia beetle consists exclusively of the ambrosia fungus that it deliberately spreads and cultivates for food. They do not feed on the wood directly; this is in contrast to other wood-boring beetles, which do feed on wood.

Prevention

In many cases, the ambrosia beetle is considered to be a net benefit to the environment, because they accelerate the decomposition of dead and dying wood. However, they can do real damage if you intend to use the wood for yourself. Infestations occur much more commonly with logging or agriculture than homes and buildings, but they can attack any lumber that’s recently been cut.

Prevention is usually focused on removing and processing wood quickly before the beetles have an opportunity to attack them. Wood should be properly stored in a safe area where the beetles cannot reach. They also need to be handled with care.

If you have trees on your property, then you should ensure they’re properly cared for and treated with mulching and water. Make sure construction or landscaping hasn’t damaged the root system that can cause stress to a tree. Once the beetle infests a plant, then the best option is to completely replace it.

The tree is unlikely to recover from that point forward because it was probably already dying or damaged in the first place. Insecticides can kill some adult beetles, but it’s difficult to apply the chemicals effectively over the entire tree. Ethanol traps are mostly intended to monitor infestations, not stop them. Fortunately, these beetles tend to do most of the damage in the wild and don’t bother people too much.