Extension Ag Update
November/December 2001
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Fall Is Good Time to Find Buckthorn

John Church, Natural Resource Educator, Rockford Extension Center, 815-397-7714

Non-native, exotic buckthorn plants have been known to be a problem in wooded and other natural areas for a number of years, due to their competitive nature. However, in the past year, it has been found that they also can be host to the soybean aphid, a new field crop pest. Exotic buckthorn varieties have been introduced to North America as ornamental shrubs. There are also native buckthorn species in Illinois, but they are less competitive.

During the summer and autumn of 2000, the soybean aphid was observed in Midwestern states. Some of the heaviest infestations were observed in northern Illinois. U. of I. entomologists also found the aphids present in soybean fields this year. The aphids feed on soybean plants and can cause stunting and reduce pod set. It has been determined that at least two types of exotic buckthorn plants are overwintering hosts for the aphids. Researchers are continuing research on the types of buckthorn that act as hosts, their typical distribution, and the degree of involvement with soybean aphid infestations in fields. Buckthorn plants do not invade soybean fields, but can be common around field edges.

In wooded or other natural areas, exotic buckthorn species shade or crowd out native vegetation. When the desirable, low growing plants are lost, bare soil is often exposed and susceptible to excessive erosion, especially on slopes and near streams and rivers. The competitive buckthorn plants can also choke out bigger shrubs, which reduces food supplies for wildlife and creates dense barriers for humans and animals to travel through.

Now is a good time to identify buckthorn, since it is one of the last shrubs to lose their leaves in the fall, it stands out more easily. Buckthorn control can be done with herbicides or controlled burns. Researchers at the Illinois Natural History Survey indicate that regular prescribed burning is the preferred method when feasible. This may be especially true for areas with abundant numbers of plants. Proper burning permits and safety control measures should be in place before burning. For isolated plants, herbicide treatments may be the most feasible.

For further information on buckthorn, its control, or the soybean aphid, contact your local University of Illinois Extension office.