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Painted Lady Irruption in the Upper Midwestern U.S.

July 5, 2019

Large numbers of Painted Ladies have been emerging in central and western Iowa and in the Omaha, Nebraska area (and most likely elsewhere in Iowa and the upper Midwest).  In central Iowa, the numbers of adult butterflies were relatively low up to and on June 27.  However, large numbers of mature 5th-instar larvae were observed feeding on thistles near Dawson, Iowa on June 17, and larvae were also reaching pest levels in some Iowa soybean fields - suggesting a huge irruption was about to occur.  Then, beginning on June 29, the next generation suddenly emerged in huge swarms, w