A beetle that farms fungus inside avocado trees could threaten crops in the U.S., Australia and Israel, says a Virginia Tech researcher. The Ambrosia beetle and its kin cultivate a very specific kind of fungus inside trees, and they could be creating new and more dangerous strains for avocado trees. They are being spread globally by infested wood pallets that are transported around the world by cargo ships.

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The beetles do their work by boring into trees where they grow a species of Fusarium fungi to feed their young. It’s the fungus that can damage or kill the trees according to Matthew Kasson of Virginia Tech, who recently received his doctorate in forest pathology from Penn State University.

The beetles are nothing new, and Kasson has found another species doing the same thing to dying or dead Tree of Heaven trees in the northeast U.S. (in contrast to the avocado trees’ ambrosia beetles which prefer to bore into live trees). The problem is that ambrosia beetles are popping up everywhere and researchers are worried that these two beetles, or their different strains of fungus, could cross to create hybrids that could threaten crops and forests.

“This really wasn’t on the radar screen of too many researchers,” said David Geiser, a plant pathologist at Penn State, who worked with Kasson on the study. “But, over the past four or five years, ambrosia beetles seem to be really out of control,” he said in Penn State press release.

“There is already strong evidence for genetic exchange between fungi from different beetles,” said Geiser. “We want to know if a beetle of one species bored into the same tree as another beetle species, can the fungi they maintain mate and produce new genotypes that are even more problematic?”

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The researchers identified nine lineages of Fusarium on ambrosia beetles. The lookalike fungi are genetically different and included the four that threaten avocado crops in Israel, Australia, California, and Florida. They published their discoveries in a recent issue of the journal Fungal Genetics and Biology.

IMAGES: Avocado cut in half. (Jamie Grill/Corbis); a female ambrosia beetle, E. validus. (Matthew Kasson)