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Issue No. 16, Article 2/July 10, 2009

Soybean Aphids Found in Illinois--Infestations Off to a Slow Start This Season

While soybean aphids have been reported for some time by entomologists in several surrounding states, this insect pest is off to a very slow start in Illinois. On July 1, Russ Higgins, IPM extension educator, found eight wingless soybean aphids on a V5 stage soybean plant just south of Morris in Grundy County. In addition to the aphids, Russ observed several adult sevenspotted lady beetles in the field. Ben Reep, Pioneer Hi-Bred International, found a winged soybean aphid on a V3-stage soybean plant near Elliott in Ford County after scouting six fields on July 1.

Also on July 1, two research teams from the Department of Crop Sciences conducted a survey for soybean aphids along two north-to-south transects in the northern half of the state. Under the direction of Ron Estes, research specialist at the University of Illinois, one team travelled along Route 47 and began sampling fields north of Gibson City, ending up just beyond Yorkville. The second team followed a path north from Eureka to just south of Rockford. Fields were randomly chosen and sampled every 20 miles; 20 whole-plant counts were taken in each field. No aphids were found in any of the 12 fields that were sampled.

Collectively these observations confirm that low densities of soybean aphids are present in widely scattered Illinois soybean fields. As we know, densities of this insect pest can increase rapidly in the absence of natural enemies, especially under mild temperatures. The soybean aphid story for 2009 has yet to be written, but it's not too early to begin scouting for aphids and natural enemies in soybean fields.--Mike Gray and Ron Estes

Mike Gray
Ron Estes

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