Invasive Triple Threat

Common Buckthorn Rhamnus cathartica
photo credit Richard Webb (www.forestryimages.com)

Recently the ALE lab and collaborators Andy Michel (OSU), Doug Landis (MSU), Matt O'Neal (ISU), and David Lusch (MSU) received a $494,000 grant from the USDA to study the impacts of common buckthorn, an invasive shrub. This plant was introduced as a landscape plant in the early 1800's and has since spread throughout the north central states. It can be found invading woodlots and agricultural fence-rows. So why is common buckthorn a triple threat? Unfortunately this plant is the overwintering host of the soybean aphid (see last week's insect of the week). This pest spends the winter in the egg stage on common buckthorn and about this time of year, hatches and begins feeding on buckthorn leaves. In early summer, the aphid disperses from common buckthorn into soybean fields.

In soybean, the soybean aphid can reach populations of thousands per plant, and producers often apply insecticides 1 or more times per year to control this pest. The presence of soybean aphid has allowed the multicolored Asian lady beetle (pictured in Chelsea's previous post and the March 19 edition of Insect of the Week) to increase in abundance. This lady beetle feeds on soybean aphid and other aphid species within crop fields.

Predation of soybean aphid by the multicolored Asian lady beetle is a positive, but unfortunately there are some significant negative impacts associated with the presence of this exotic lady beetle. First, this is the lady beetle that invades homes in the fall looking for a place to spend the winter. In addition to being an annoyance, some people have asthmatic reactions to their presence. Second, in the late fall multicolored Asian lady beetles can move into vineyards and feeds on ripe grapes. When the grapes are harvested the beetles become a contaminate in wine, giving it a distinctive bitter taste. Finally, the multicolored Asian lady beetle has been implicated in the decline in native lady beetles. It is known to eat the eggs and larvae of other lady beetle species.

The multi-state research team studying the impacts of common buckthorn will be examining whether the abundance of buckthorn in the landscape influences the abundance of soybean aphid and multicolored Asian lady beetle. Our goal is to determine if the presence of buckthorn has facilitated the success of these other invasive species, and if so determine the spatial scale at which buckthorn removal efforts should be made to reduce the impacts off this entire invasive triple threat.

Recently we were interviewed about this project by science reporter Spencer Hunt of the Columbus Dispatch. To read the full article on the project click on the "share me" link below.

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