Identifying Weed Threats to Ohio Soybean Production
Agronomy & Pest Management
Stephanie Karhoff
Field Specialist, Agronomic Systems
The Ohio State University
Ottawa
Abstract
The Ohio State University Extension Pre-Harvest Soybean Weed Survey is an annual statewide effort designed to document weed escapes and identify emerging management challenges for Ohio growers. The primary objective of the survey is to quantify the frequency, distribution, and severity of problematic weed species present in soybean fields immediately prior to harvest. In 2025, Extension educators evaluated 4,459 soybean fields across 47 counties visually assessing weed infestations. Each field was rated on a three-point scale representing low, moderate, or severe infestations for observed species. The most frequently observed weeds statewide were waterhemp (17% of fields), volunteer corn (15%), marestail (10%), grasses/foxtail species (10%), and giant ragweed (9%). Approximately 48% of surveyed fields were free of weeds, a slight decline compared with the previous year. Waterhemp continued to increase in frequency and severity, becoming the most common weed observed in 2025 and demonstrating particularly high pressure in western Ohio. In fields where waterhemp occurred, 25% were rated as severe infestations, highlighting the growing management challenge associated with this species and its capacity for rapid growth, high seed production, and widespread herbicide resistance. The findings are summarized annually by crop reporting districts and shared along with weed management curriculum with OSU Extension Educators to be used in county programming. Results are also shared directly with crop consultants and industry representatives. Overall, the survey provides important insights into statewide weed management trends and supports the development of targeted Extension programming by documenting weed escapes and shifts in species prevalence.
Authors: Stephanie Karhoff, Alyssa Essman
-
Stephanie Karhoff Field Specialist, Agronomic Systems, The Ohio State University, Ohio, 45875
-
Alyssa Essman Assistant Professor, The Ohio State University, Ohio, 43210