2023 Preharvest Weeds Survey

November 27, 2023
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Each year just before harvest, the weed science team at OSU spends some time driving across the state and evaluating weed escapes in soybean fields. This year, 4027 fields were evaluated across 46 of the top soybean producing counties. We collected information on the frequency and distribution of 10 weed species, namely: marestail, giant ragweed, common ragweed, waterhemp, Palmer amaranth, redroot pigweed, volunteer corn, common lambsquarters, giant foxtail/grass, and velvetleaf. This allows us to evaluate the efficacy of management programs, monitor escapes, and forecast potential issues and threats for the next growing season.

In 2023, 48% of fields encountered on the survey were clean, or at least free of the 10 weeds being evaluated. The most commonly encountered weed this year was volunteer corn, which was found in 17% of fields. In second was giant ragweed at 14%, closely followed by waterhemp at 13%. The other two species among the top 5 were marestail/horseweed and grass/foxtail spp.

The most commonly encountered weeds – percent of total fields:

  1. Volunteer corn – 17%
  2. Giant ragweed – 14%
  3. Waterhemp – 13%
  4. Marestail/horseweed – 10%
  5. Grass/foxtail spp. – 9%

The most concerning outcome was that we once again encountered waterhemp at a higher frequency than in previous years, based on percent of fields encountered with waterhemp present. This year, waterhemp was found in 89% of surveyed counties and in 13% of total fields (Figure 1). In 2022, waterhemp was present in 93% of surveyed counties in Ohio and in 11% of the total fields encountered. Waterhemp in 2021 was found in 77% of counties and in 7% of surveyed fields. In 2020, pigweeds combined across species (waterhemp, Palmer amaranth, and redroot pigweed) were found in 89% of surveyed counties and in 8% of fields.

Information on the biological characteristics of waterhemp and results of previous herbicide resistance screenings were covered in an article published last year: Waterhemp on the Rise. For more information on the prevention and management of waterhemp populations, visit our website or reach out to Alyssa Essman, Essman.42@osu.edu.