Soybean aphid suction trap network

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Northcentral Regional Aphid Suction Trap Network was turned on last week in at least eight states. As in 2005, Michigan has three trapping locations that cover a north-south transect:  MSU’s Saginaw Valley Bean and Beet Research Farm in Saginaw County; the MSU Entomology Farm in Ingham County; and the Kellogg Biological Station in Kalamazoo County.  By the end of June, we will set up two new locations: one at the MSU Extension office in Monroe County to cover southeast Michigan and another in western Michigan in Oceana County.  Monroe County has a high population of buckthorn, the overwintering host for soybean aphid; it experienced heavy, early aphid infestation in 2005, and thus may benefit from trapping information.  The location in Oceana County is specifically targeted to provide information to vegetable growers in Western Michigan, where soybean aphid is implicated in virus spread.

The traps suck in migrating insects, including winged aphids, flying over 20 feet above the ground.  The insects end up in a jar of antifreeze just above the fan in the base of the trap.  Sample bottles are changed weekly and mailed to the University of Illinois where aphids are removed, identified and counted.  The soybean aphid counts are posted on a web site,, where you can view individual traps from each of the eight states. There are currently 33 traps on the network, plus 5 to 6 more that will come on line in June.

How can you use the suction trap data?

In early to mid-July, increasing flight tells you that winged soybean aphids are being produced in early infested fields and are now dispersing across the landscape. These infested fields could be local, in another part of the state or even in a neighboring state.  This means that previously uninfested, low-infested fields or seed-treated fields may get an influx of landing aphids that leave babies behind. This is how fields in areas that lack buckthorn (for example, many locations in southwest Michigan) get infested in July.

Later in the season, in late July and early August, increases in flight often time with peak infestations in soybean fields.  For example, last season (see the 2005 data at, tremendous numbers of soybean aphids were trapped in early to mid-August, when aphid populations peaked in nearby fields.  Such heavy aphid flights increase the risk of reinfestation in previously-sprayed fields we certainly experienced that frustrating situation in 2005.

In the last four years, heavy aphid flights in late July/early August coincided with virus infection in vegetable crops in Michigan. The suction traps can alert growers to a potential virus threat and may eventually help vegetable growers make decisions about late-plantings, for example, variety selection.

At the end of the season, the suction traps play their most important role, potentially predicting next year’s soybean aphid population.  Suction traps catch the winged males and females that leave soybean and go back to buckthorn, where soybean aphid overwinters.  In Illinois, the number of fall migrants caught in suction traps correctly predicted the next year’s aphid population (outbreak versus no outbreak) in four out of four seasons, including 2005. The 2005 season was the first year for the Regional network, across eight states. At the end of 2005, some areas (such as Michigan) had low fall trap catches; others (for example Minnesota) had high fall flights.  June 2006 is a critical test for the predictability of the traps in theory, Michigan should have low colonization this spring and Minnesota should have early, heavier colonization.  Stayed tuned!

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