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Study finds invasive insects are developing 'toxic shields': 'Chemical defenses against avian predators'

It suggests that nature's own pest control may be less effective than many had hoped.

A small bird perched on a twig, surrounded by blurred green foliage.

Photo Credit: iStock

New research out of Penn State suggests that spotted lanternflies may be gaining built-in "toxic shields" against birds, an alarming development in the fight against the invasive pest.

In a study published in the peer-reviewed Journal of Chemical Ecology, Penn State entomologists said several bird species were less likely to eat the invasive bugs after they fed on tree of heaven, another invasive species.

The Penn State research team, led by postdoctoral researcher Anne Johnson in the College of Agricultural Sciences, wanted to test whether birds could help reduce spotted lanternfly populations. These insects, originally from Asia, have become notorious for damaging crops and putting pressure on local agricultural economies.

The entomologists hypothesized that, after feeding upon the tree of heaven, spotted lanternflies stored bitter chemicals from the plant in their bodies and eggs, protecting against avian predation. They then used the lanternflies in bird-feeding trials, with house wrens tested in nest boxes. 

The birds generally chose lanternflies that had not fed on the tree of heaven. The wrens also consumed more, or gave more to their chicks, when the insects came from the group kept off the plant, according to the Penn State press release.

After conducting the study, Johnson noted that "we found that birds, including nesting house wrens, preferred to eat spotted lanternflies that had not fed on tree of heaven, suggesting that the insects that consume this plant are less tasty, thereby providing some chemical defenses against avian predators." 

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The chemicals, quassinoids, essentially create what the PSU press release on the finding described as a "toxic shield."

The study is quite significant because it suggests that nature's own pest control (birds) may be less effective in controlling the invasive insects than many had hoped, especially in communities already dealing with damage to vineyards, orchards, and plant nurseries.

And considering that estimates predict that the spotted lanternfly could cause hundreds of millions of dollars of economic damage in the Pennsylvania agricultural sector alone, these toxic shields could be quite costly to society.

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