The next generation of thistle caterpillars is making an appearance in central Iowa soybean. I have not received any reports of significant defoliation by this insect. Thistle caterpillars are easily recognized by the multibranched spines, which resemble Christmas trees that have lost their needles. The larvae are mostly black and yellow with no distinctive pattern. The adult butterfly, called the painted lady, is common along roadsides this summer.
Iowa State University
Rice, Marlin E., "Thistle caterpillars are webbing soybean leaves" (2001). Integrated Crop Management News. 1993.
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