Farm Progress

Farmstead Forest: Study seeks to control invasive bush in woodlands, as it hosts crop pest in winter.

June 4, 2018

2 Min Read
APHID CONTROL: A new study in Minnesota is looking at how controlling buckthorn could alleviate soybean aphid damage, because the invasive shrub serves as an overwinter host for aphid eggs.Marcella Windmuller-Campione

Do you have problems with periodic soybean aphid infestations? If you do, buckthorn may be a potential cause.

Common or European buckthorn, members of the genus Rhamnus, is an invasive, understory shrub that was first brought to North America for windbreaks, hedgerows and landscape purposes in the 1850s. Growing to heights of 25 feet, it can outgrow native plants, survive extreme weather and cause problems for wildlife, as well as wetlands, prairie and native forests. It also serves as a host plant for overwintering soybean aphid eggs.

Soybean aphids are an invasive insect native to Asia that were discovered in Midwestern soybean fields in 2000. They use sucking, needle-like mouth parts to extract plant fluids, and their waste, known as honeydew, can promote the development of sooty mold on soybean leaves, reducing photosynthesis in the plants and reducing yields.

Much of the focus in controlling aphid damage to soybeans has centered on scouting aphids in midsummer and spraying fields that reach the economic threshold level of aphid populations.

Because buckthorn serves as a winter host for aphid eggs, a new interdisciplinary study by the University of Minnesota will look at controlling buckthorn in woodlands adjacent to soybean fields. Recent research at UM and in Ontario has established the relationship between buckthorn and early-season aphid populations. UM researchers, with assistance from the Minnesota Soybean Research and Promotion Council, are hoping to look at how buckthorn density levels impact soybean aphid populations, and how buckthorn management could lower the risk for aphid damage.

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“We have about 30 farmers that we’re working with in central and southern Minnesota,” says Marcella Windmuller-Campione, assistant professor at the UM Department of Forest Resources. “The farmers volunteer their fields throughout the growing season for sampling, and we share information about their individual fields, what their woodlands look like and soybean aphid numbers.” 

Although previous research into this relationship is limited, one hypothesis is that early-season spread of soybean aphid is related to buckthorn density and proximity to soybean fields. This was observed in prior Ontario research. Now, researchers have begun to look at Minnesota buckthorn populations, which are much higher than those observed in the Ontario study.

Windmuller-Campione says buckthorn is prevalent and likely underdetected across Minnesota, with an average of 1,228 stems per acre in the fields of project cooperators. “Part of our project was mapping buckthorn and soybean aphid, and we will be working to put that map into a peer-reviewed publication,” she says. “Buckthorn is a damaging invasive shrub, and it takes consistent management to control. If we can demonstrate that reducing buckthorn populations can also aid in reducing soybean aphid populations, there is a real potential to kill two birds, or two invasive species, with one stone by removing the buckthorn.”

Learn more at myminnesotawoods.umn.edu

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