Chemical signals from fungi indicate bark beetles that infest trees

Fungi can help some killer tree beetles turn the tree’s natural defense system against itself.

Eurasian spruce bark beetleThe printer himself) killed millions of walnuts in forests across Europe. Already, research suggests that fungi associated with these beetles are key players in host insect infestations. These fungi distort host trees’ chemical defenses to create an odor that attracts beetles to crawl, researchers report on February 21. PLOS Biology.

This would be the reason why the bark beetles would tend to examine the same tree. As climate change makes Europe’s forests more vulnerable to insect attacks, understanding this relationship will help scientists devise new measures to ward off insect attacks.

Bark beetles are a type of insect found around the world that feed and reproduce inside trees.SN: 12/17/10). Over the years, several species of beet bark have invaded forests from North America to Australia, leaving a trail of dead trees in their wake.

But trees are not helpless. Conifers — which include pines and firs — are real chemical weapons factories. The green scent of Christmas trees and alpine forests rises from the air of these economic varieties. But while they may smell pleasant, the main purpose of these chemicals is to trap and poison invaders.

Or at least you wanted to do it.

“Conifers are full of resin and other material that must be repulsive to insects,” says Jonathan Gershenzon, a chemical ecologist at the Max Planck Institute for Chemical Ecology in Jena, Germany. “But the bark beetle doesn’t seem to mind at all.”

This ability of bark beetles to attack the strong defense system of conifers has led some scientists to wonder if fungi could help. Fungi break down compounds in their environment for food and protection (SN: 11/30/21). And play some kind, even some species in a kind Grosmannia — always in association with Eurasian spruce bark beetles.

Gershenzon and his associates compared the bark of the infested spruce to the released economy Grosmannia and other fungi for the chemical composition of infected trees. The presence of fungi fundamentally changed the chemical composition of spruce, the team found. More than half of the chemicals in the air — monoterpenes and other chemicals that are likely part of the tree’s defense system released by the fungus — were unique to the infected trees after 12 days.

This is surprising because researchers had previously assumed that invading fungi barely changed the chemical makeup of trees, says Jonathan Cale, a fungal ecologist at the University of Northern British Columbia in Prince George, Canada, who was not involved with the research.

Later experiments revealed that bark beetles can detect many of these chemicals produced by fungi. The team tested this by applying tiny electrodes to the beetles’ heads and detecting electrical activity when the chemicals emitted passed through their antennae. Indeed, the scent of these chemicals mixed with the beetle’s pheromones led the insects to dig at higher rates than the scent of the pheromones alone.

The study suggests that these fungal chemicals may help the beetle where it feeds and reproduces, perhaps by advertising that the fungus has taken down some of the tree’s defenses. The fine nature of the chemicals could also explain the behavior of beetles that cause the death of healthy mature trees.

But while the smell of mushrooms exhales trees, it can also lead to the destruction of beetles. Beetle traps in Europe now use only beetle pheromones to attract their victims. By combining pheromones with chemicals derived from fungi, the secret would be to attract more beetles to the traps and make them more effective.

The results present “an exciting opportunity to develop new tools to manage destructive beetle outbreaks” for other beetle species as well, Cale says. In North America, mild winters and drought have put conifer forests at greater risk from mountain pine beetles (Dendrocton pendersoae) attack The discovery and use of a fungus-based economy could be one way to ward off the worst bark beetle infestations in the years to come.