The Ambrosia Beetle Megaplatypus mutatus: Tiny but Destructive

By David Coyle, Ph.D.

Although ambrosia beetles are a crucial part of natural systems around the world, helping to break down woody material and recycle nutrients, these tiny insects are rarely noticed except by those actively working with (or looking for) them. They spend most of their lives inside woody things, like a tree stem or branch, making them difficult to just casually bump into. They are attracted to alcohol—stressed trees and shrubs emit ethanol, which ambrosia beetles typically use to find their hosts—and can sometimes be seen hovering nearby if you’re enjoying an adult beverage outside. (They sort of look like little, slow-moving flies.) The point is, they’re everywhere, even if unnoticed.

While most of them aren’t aggressive tree killers, some are, like the redbay ambrosia beetle (Xyleborus glabratus), which spreads laurel wilt disease in the southeastern U.S., or the Euwallacea spp. shot hole borers in the southwestern U.S. Invasive species researchers are always watching for what might be the next impactful pest to come into North America, and one such candidate was profiled in a new article in August in the open-access Journal of Integrated Pest Management.

Megaplatypus mutatus is an ambrosia beetle that is native to South America but has since been discovered in Europe. As lead author Esteban Ceriani-Nakamurakare, Ph.D., and colleagues at the National Scientific and Technical Research Council in Argentina explain, in this species, the male initiates the gallery in a healthy tree and calls in females using pheromones. Both adults and larvae extend the tunnels, which eventually weaken the tree, lead to stem or branch breakage, and often tree death. Their ability to increase populations rapidly is impressive—in some cases, nearly 1,000 progeny have come from a single mated pair! This species has a broad host range, infesting both hardwoods and conifers.

Management of Megaplatypus mutatus is difficult because of the broad host range, cryptic lifestyle, and complex interactions with several fungal species (which it carries and transmits to the during gallery formation). Chemicals are typically not useful for ambrosia beetles, and thus far little has been done to examine biological control agents. Small infestations can be removed and managed with sanitation activities (i.e., removing and destroying all affected trees). Since this species relies on communication via pheromones to find mates, disrupting this process may prove as the most useful avenue for future research toward effective management strategies. Ultimately, like all non-native and potentially invasive species, the best thing we can do is prevent Megaplatypus mutatus from getting here in the first place.

David Coyle, Ph.D., is an assistant professor in the Department of Forestry and Environmental Conservation at Clemson University. Twitter/Instagram/TikTok: @drdavecoyle. Email: dcoyle@clemson.edu.