July 25, 2019
Issue 6

Thistle Caterpillars:    We are now experiencing the second generation of thistle caterpillars - read more about the life cycle here . Larvae from thistle caterpillars damage the soybean crop by consuming leaf tissue or defoliating the soybean plants.
This second generation will pupate fairly soon. Some thistle caterpillars are dying of natural causes - check the population before treatment is applied.
Treatment may be necessary if defoliation exceeds 20% during these early reproductive stages. This article has some good guidelines to estimate defoliation .
This insect is fairly easy to control. Labeled soybean insecticides applied so far have been effective to manage this insect.
Two generations of this insect are expected -it is not known if there will be a third generation. The third generation would appear in mid-August and may coincide with insecticide applications for soybean aphid.
Prepared by:
  Paul Kassel- Extension Field Agronomist


Phone:  (712) 262-2264


Serving Clay, Buena Vista, Dickinson, Emmet, Hancock, Kossuth, Palo Alto, Pocahontas, Sac and Winnebago Counties



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