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Central Iowa Crop Update
Updates from an agronomist and weed nerd in central Iowa.
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In this issue:
- Aug. 28 Ag Engineering and Agronomy Farm Field Day
- 3rd generation thistle caterpillars out but hopefully small
- Weather conditions and crop development
- Potassium deficiency and other upper canopy ailments of soybean
- Soybean gall midge present in Dallas and Madison Co.
- Scout for corn earworm in corn fields
- Aphids showing up in soybean fields
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Aug. 28 Ag Engineering and Agronomy Farm Field Day
Next Wednesday, August 28, is the Ag Engineering and Agronomy Farm Field Day between Boone and Ames. This field day will start at 9:00 a.m. and include a welcome from the new Dean of the College of Ag and Life Sciences at ISU, a weather update from Dennis Todey, and a demonstration and discussion on soil compaction and equipment from Mark Hanna. Attendees can receive 2.5 Soil and Water Certified Crop Adviser (CCA) CEUs at the event. The field day will conclude at noon with a free lunch! Please join us for this great event!
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3rd generation of thistle caterpillars out but hopefully small
The third generation of thistle caterpillars are out and feeding in central Iowa soybean fields. These caterpillars will develop over the next several weeks, pupate, and hopefully fly south.
The threshold for treatment remains the same, 20% defoliation (whole plant, across the field), so it should be more difficult for caterpillars to consume enough tissue to reach this threshold now that plants are more mature, but caterpillar populations may be bigger as well. This article from the University of Nebraska-Lincoln has a nice graphic to demonstrate a quick method to scout for defoliation. As has been the case throughout the season, it seems the later planted fields will probably be at more risk (in general). See photos below of new caterpillars out in soybeans late last week.
Photo of the 3rd generation of thistle caterpillars from August 15 (4 larvae on one trifoliate leaf).
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