Bark beetles use the smell of fungus to pick the best trees to infest

Trees with fungal infections produce odours that appeal to bark beetles, which burrow into the bark and might devastate complete forests

By Corryn Wetzel

Bark beetles could use receptors of their antennae to detect and feast on fungus-infected timber.

The Eurasian spruce bark beetle (Ips typographus) – present in Europe, Asia and a few elements of Africa – burrows into the bark of Norway spruce (Picea abies) the place it feeds and reproduces. In doing so, 1000’s of the pine-nut-sized bugs can kill big swaths of forest.

Researchers already knew that bark beetles most well-liked to assault timber weakened by sure fungi, probably as a result of fungi present the bugs with protecting advantages from bothersome microbes and parasites, and will complement the beetles’ eating regimen. “They gang up and take down huge trees,” says Jonathan Gershenzon at Max Planck Institute for Chemical Ecology in Germany.

But how the beetles had been sensing their contaminated hosts was not recognized. Gershenzon and Dineshkumar Kandasamy at Lund University in Sweden investigated this by figuring out compounds launched by the spruce timber contaminated with Grosmannia penicillata, a fungus nearly at all times present in timber which have succumbed to bark beetle. They discovered that the fungus created two major chemical compounds: camphor and thujanol.

Next, the researchers examined the beetles‘ anatomy and located scent-detecting neurons of their antennae that may detect camphor and thujanol. When they gave the bugs their alternative of wholesome or G. penicillata-infected spruce bark within the lab, all the beetles had been extra interested in the fungus-damaged wooden. The presence of the fungus-produced compounds not solely attracted the beetles but additionally spurred them to tunnel into the bark.

When tree bark was contaminated with a sort of fungus that wasn’t useful to the beetle – and which produced totally different chemical compounds – the bugs weren’t interested in the wooden. “The beetles have evolved to sense the beneficial fungus… and avoid or ignore the ones that are not good for them,” says Kandasamy.

A extra thorough investigation of which fungi produce chemical substances which might be enticing to the beetles would have strengthened the research, says Jiri Hulcr on the University of Florida. “We cannot say that… G. penicillata is particularly special. It may be a natural function of any member of the microbial soup that grows inside a dead tree.”

The researchers are optimistic that pinpointing bark beetle-attracting compounds may result in simpler baiting efforts. Currently, researchers use a cocktail of enticing pheromones to lure the beetles right into a lure en mass, however the technique “hasn’t been that successful in the cycle of outbreaks that have started in the last 10 years”, says Gershenzon. He hopes including these fungi-related compounds to traps may increase their effectiveness.

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