Simulated herbicide drift alters native plant flowering phenology

• Published in: Ecotoxicology (London) 2024-11, Vol.33 (9), p.1009-1025
• Main Authors: Olszyk, David, Pfleeger, Thomas, Shiroyama, Tamotsu, Blakeley-Smith, Matthew, Lee, E. Henry, Nash, M. S., Plocher, Milton
• Format: Article
• Language: English
• Subjects: Buds; Developmental stages; Dicamba - toxicity; Drift; Drift rate; Earth and Environmental Science; Ecology; Ecotoxicology; Environment; Environmental Management; Eriophyllum lanatum; Experimental farms; Farms; Flowering; Flowering plants; Flowers - drug effects; Glycine - analogs & derivatives; Glycine - toxicity; Glyphosate; Herbicides; Herbicides - toxicity; Indigenous plants; Indigenous species; Iris tenax; Oregon; Phenology; Plant layout; Plant reproduction; Plant species; Plants; Plants (botany); Prunella vulgaris; Seed production; Seeds
• ISSN: 0963-9292; 1573-3017; 1573-3017
• DOI: 10.1007/s10646-024-02795-3

Data for herbicide effects on plant flowering are needed to determine potential impacts on plant reproduction. Thus, flowering phenology was determined for up to 12 weeks after herbicide treatment for native Willamette Valley plants growing in small plots on two Oregon State University experimental farms. Six perennial species were evaluated: Camassia leichtlinii (CALE), Elymus glaucus (ELGL), Eriophyllum lanatum (ERLA), Festuca idahoensis subsp . roemeri (FEID), Iris tenax (IRTE), and Prunella vulgaris var. lanceolata (PRVU). Effects of glyphosate and dicamba, alone and in combination, were determined using simulated drift rates of 0.1 or 0.2 x field application rates (FAR) of 1119 g ha −1 active ingredient (a.i.) (830 g ha −1 acid glyphosate) for glyphosate and 560 g ha −1 a.i. for dicamba. Flowering phenology was evaluated as stage of development on a scale from no buds (converted to 0), buds (1), pre-flowering (2), flowering (3), post-flowering (4), to mature seeds (5) before herbicide treatment and for 12 weeks after treatment. Flowering response to herbicides varied by species and farm; but, in general, dicamba and glyphosate resulted in earlier flowering stages (delayed or not full flowering) for the dicot ERLA, and to a lesser extent, PRVU; and glyphosate resulted in earlier flowering stages for the monocot IRTE. Based on these data, the concentration of herbicide affecting flowering stage was 0.1 x FAR. Once flowering stage was inhibited by dicamba and glyphosate, plants generally did not recover to full flowering. This study provided evidence that common herbicides can affect flowering phenology of native plants with implications for seed production. Highlights Flowering phenology (stage of development) of six perennial plant species was evaluated in the field after treatment with dicamba and/or glyphosate. Dicamba and glyphosate resulted in delay of flowering (earlier stages of development) for dicots, especially Eriophyllum lanatum and, to a lesser extent, Prunella vulgaris var. lanceolata . Glyphosate resulted in delay of flowering for the monocot Iris tenax . Flowering stage was affected by 0.1 x a field application rate of 1119 g ha −1 active ingredient (a.i.) (830 g ha −1 acid glyphosate) for glyphosate and 560 g ha −1 a.i. for dicamba. Once flowering stage was inhibited by herbicides, the plants generally did not recover.