News Bark and ambrosia beetles: small beetles, big impact

Bark and ambosia beetles are tiny beetles (barely 1.5–10 mm in size) that live in wood (Fig. 1). They seem harmless, but once they establish themselves in large numbers, they can have a massive impact on trees in forests, parks, and tree nurseries, resulting in significant tree mortality. They attack both coniferous and deciduous trees and create superficial tunnels in the trunk and branches of the tree. They easily hitch a ride under the bark during international timber transport (Fig. 2), allowing them to spread worldwide while escaping notice.

Two recent research projects, SCOLIBE and METASCOL, are helping to better map these beetles and ensure more efficient detection and control.

SCOLIBE: Mapping High-Risk Beetles

In the SCOLIBE project, scientists delved into the habitats of 165 beetle species known for their invasive behavior. They wondered which of these species might establish themselves in Belgium and what damage they could cause here.

By combining climate data, host plants, and information from previous problems with these beetles, the team created a clear ranking. This resulted in four priority lists that help determine which species we should focus our attention on. Some of the species at the top of these lists include Platypus apicalis, Scolytus kirschii kirschii, Trypophloeus striatulus, Phloeotribus liminaris, and Ips duplicatus. The latter species is rapidly approaching Belgium: it is currently spreading from Northeast Europe and is already present in Austria and Switzerland. So, we need to be on our guard.

Ips duplicatus, like the European spruce bark beetle (Ips typographus), occurs on spruce and fir. Both species look very similar, but Ips duplicatus is slightly smaller (2.8 to 4.5 mm vs. 4.2 to 5.5 mm for the European spruce bark beetle). The two species are usually distinguished based on the shape of the four “teeth” at the rear of the elytra (Fig. 3).

Extensive field experiments were conducted using various types of traps. The surprising result? Small, widely spaced fan traps (Fig. 4) proved to be the most effective for detecting the greatest diversity of species. This knowledge is essential for those working in ports, warehouses, or tree nurseries to prevent new introductions of these beetles into our country.

METASCOL: DNA Identification as the New Standard

While SCOLIBE focused on risk assessment and monitoring strategies, METASCOL addresses a different challenge: accurately identifying the correct species.

Until now, this has mainly been done under a microscope—a time-consuming process that requires taxonomic expertise. But that expertise is becoming increasingly scarce.

That is why METASCOL is investigating how DNA metabarcoding can be utilized. This is a technique in which DNA from beetles in litter is analyzed to identify all present beetle species in a single step. The researchers are comparing different methods, building extensive DNA reference databases, and testing which approach is the most reliable.

The goal of this recently launched project? A fast, accurate, and large-scale method for detecting bark beetles, so that monitoring teams are no longer dependent on rare specialists.

Why This Research Matters

The combination of SCOLIBE and METASCOL represents a significant step forward in protecting our forests. We now have a better understanding of which species pose the greatest risk, how best to detect them, and how to identify them quickly.

This paves the way for a future in which harmful beetles are no longer invisible invaders, but are detected and addressed early on—before they can cause damage.

What does ILVO do?

The Plant Diagnositic Center (DCP) regularly receives wooden packaging material that may contain wood-boring beetles, such as bark beetles. The FASFC also regularly sends us beetle traps that they have placed in Belgian forests. The DCP’s task is to determine whether these samples contain quarantine or only permitted (European) beetle species and, in the event that a quarantine beetle is found, to report this immediately to the FASFC.