S-Metolachlor Crop Safety – 2024

Research Summary Abstract

From 2004 to 2023, IR-4 completed 258 trials on Pennant Magnum (s-metolachlor). The data contained in this report was generated to register uses of s-metolachlor on and around environmental horticulture plants with over-the-top applications. The s-metolachlor rates in the testing program were 2.5, 5.0, and 10.0 pounds active ingredient per acre (lb ai per A) as the 1X, 2X and 4X rates with 4, 6, or 8 week intervals between applications. Pennant Magnum has been applied to 136 plant genera or species. Of these, 14 plant species exhibited no or minimal transient injury after application at all three rates. Thirteen (13) crops exhibited no phytotoxicity at 2.5 lb ai per acre but did have some injury at 5.0 and/or 10.0 lb ai per acre. Twenty-five (25) crops exhibited significant phytotoxicity at even the lowest rate. For 11 crops, the response among sites was variable, and 40 crops have less than three trials completed.

Link to Summary: S-Metolachlor Crop Safety Summary