Scale Insects May Flourish with Climate Change, Destroy Trees

New research indicates that scale insects may be able to flourish, even among global climate change, and their increased presence threatens to weaken and kill trees.

Researchers from North Carolina State University have found that century-old museum specimens hold clues to how climate change will affect this common insect pest.

"Recent studies found that scale insect populations increase on oak and maple trees in warmer urban areas, which raises the possibility that these pests may also increase with global warming," lead author Dr. Elsa Youngsteadt, a research associate at NC State, said in a news release.

This problem was found to be true in cities, but researchers wanted to know if it applied to rural areas as well. To address that question, Youngsteadt examined more than 300 museum specimens of red maple branches collected from 1895-2011 in rural areas of North Carolina, South Carolina and Georgia. After evaluating the scale insect remains attached to each specimen, researchers estimated scale population density and compared it to the average August temperature in each area they were collected in.

Youngsteadt then compared the findings from the historical specimens with more recent data from urban Raleigh, N.C.

"Scale insect density in rural areas was not as high as it was in the city, but there was a common pattern," Youngsteadt explained. "Scale insects were most likely to be present on specimens collected during warm historical time periods, and scales were most abundant when temperatures were similar to modern, urban Raleigh."

And naturally, researchers expected that scale insects would be more abundant in rural forests today compared to previous years, given recent climate warming.

To test the theory, Youngsteadt compared specimens from 20 different sites to modern-day populations.

"Sure enough, scale abundance had increased at 16 of the 20 sites," he said. "Overall, we found a total of about five times more scale insects in 2013 than on the historical specimens from the same locations.

The results were published in the journal Global Change Biology.