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Protoporphyrinogen oxidase (PPO)-inhibiting herbicides (HG 14) inhibit the production of chlorophyll. PPO-inhibiting herbicides minimally translocation through plants, thus the injury will only occur where the spray droplets come into contact with the soybean plant. Injury incurred by PPO-inhibiting herbicides applied pre-emergence includes necrosis on the margins of cotyledons and leaves (Image ). Injury can occur via having treated-soil water-splashed onto the emerging plant or contact with the herbicide in the soil-water as the plant emerges. Soybeans injured by PPO-inhibiting herbicides applied pre-emergence can result in plant death if the hypocotyls are chemically-excised. Injury incurred by PPO-inhibiting herbicides applied post-emergence includes speckled-necrosis and plant stunting (Figure 1). The development of PPO-inhibiting herbicide injury will be rapid and injury will be greater on hot, humid days. The injury caused by PPO-inhibiting herbicides on soybeans will subside with 7 to 14 days after application. Labeled rotation restrictions should be followed to ensure that crops following soybeans are not injured by carryover of PPO-inhibiting herbicides.

PPO-inhibiting herbicide injury

Figure 1. PPO-inhibiting herbicide injury on soybeans applied pre-emergence.

Author

Extension Weed Specialist and Associate Professor
Crop & Soil Sciences

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Publication date: Jan. 22, 2021

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N.C. Cooperative Extension prohibits discrimination and harassment regardless of age, color, disability, family and marital status, gender identity, national origin, political beliefs, race, religion, sex (including pregnancy), sexual orientation and veteran status.