Fighting unwanted insects -- with more insects

            When Jean Williams discovered a blood-red beetle with long black antennae consuming the lilies in her Wakefield garden a decade ago, she recognized it at once as an invasive insect she had just learned about in a gardening class. University of Rhode Island researchers had been on the lookout for the new invader, which until then had not been found in South County. So she called URI entomologist Richard Casagrande, who verified that the insect was a lily leaf beetle, a Eurasian species responsible for wiping out populations of native and ornamental lilies in much of the Northeast.

            Today, the beetle is not nearly the pest it was back then. That’s because Casagrande and colleague Lisa Tewksbury identified the beetle’s natural enemy in Europe, a tiny parasitic wasp, and have been raising and releasing small numbers of them wherever lily leaf beetles have been found in the region. The wasps lay their eggs exclusively in the larvae of lily leaf beetles, and when the eggs hatch, the wasp larvae kill and consume the beetle larvae from the inside.

            “The wasps are such teeny weeny little iridescent things that I had no fear of them at all,” says Williams of the insects released in her garden. “By the following year, they were definitely starting to control the beetles, and within a few years the beetles were mostly under control.”

            Casagrande calls the parasitic wasp “fabulously successful” at controlling the lily leaf beetle. He and Tewksbury have released the wasps in numerous locations in Rhode Island and Massachusetts, and they have shipped them to New Hampshire, Maine, Connecticut and Ontario for release by partner researchers in those locations. Everywhere the wasps have been released, the lily leaf beetle population crashes within a few years, making the wasp an ideal poster child for what is known as biological control.

            The invasion of non-native species like the lily leaf beetle is a growing problem that has significant implications for native biodiversity, human health and the economy. Once an invasive species becomes established, it is a costly and challenging undertaking to get rid of it using chemical pesticides, mechanical means and other strategies. Despite the research required to do it safely, biologicalcontrol – what the U.S. Fish and Wildlife Service calls the purposeful use of an invasive species’ natural enemies to reduce populations – is often the most successful strategy for eradicating invasives....

Read the complete story in the September 2016 issue of Rhode Island Monthly.