Paving the Way For Invasive Species

Horticulturalists help bring beauty to our gardens and landscapes by introducing plants from other parts of the world and breeding them for aesthetic characteristics. In the past, not enough attention was paid to the potential for these plants to become invasive. After several incidents of horticultural plants invading the landscape, horticulturalists are more aware of the potential harm and evaluate the possibility that an introduced plant will become invasive.

Buckthorn, Rhamnus cathartica, is a European Plant that was introduced to North America as an ornamental in the 1800s. Used as a hedgerow plant in landscapes, buckthorn produces berries that are spread by birds and forms impenetrable hedgerows in the forest. It thrives as an understory plant where it displaces native vegetation, destroys wildlife habitat, and prevents growth of native tree saplings. Currently there are prohibitions against planting buckthorn in North America and efforts are made to remove or manage invasive buckthorn populations.

Soybean Aphids on Buckthorn Leaves

It is Fall in Indiana and an invasive insect is in the air. Soybean aphids, an invasive pest first detected early this century is leaving senescing soybeans in search of an overwintering host. The primary soybean aphid overwintering host is buckthorn. Without the introduction of buckthorn and its invasion of the landscape, soybean aphid would have had far more difficulty locating overwintering hosts and likely have been far less of a pest problem or even would have failed to establish. Decisions to import buckthorn plants over a century ago, have altered the North American ecosystem in a way that makes it more favorable for soybean aphid. Who could have predicted that planting a hedgerow in the 1840s could make a major contribution to crop pests a century and a half later?