Granular Preemergence Applied Herbicides Influence Annual Bedding Plant Growth

Mack Thetford,J David Williams,Charles H Gilliam

doi:10.24266/0738-2898-13.2.97

Mack Thetford, J David Williams + Show 1 more

Open Access

https://doi.org/10.24266/0738-2898-13.2.97

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Abstract

Abstract Three experiments were conducted to evaluate effects of preemergence applied herbicides on annual bedding plants. In experiment 1, five preemergence applied herbicides were evaluated for control of large crabgrass (Digitaria sanguinalis L. Scop.) and prostrate spurge (Euphorbia humistata Engelm. ex Gray) and phytotoxicity to spring planted herbaceous bedding plants. Dimension 0.5G (dithiopyr) applied at 1.1, 2.2 or 3.4 kg ai/ha (1.0, 2.0, or 3.0 lb ai/A), Southern Weedgrass Control (SWGC) (pendimethalin) 2.68G and Rout 3G (oxyfluorfen + oryzalin) each applied at 1.7, 3.4 or 6.7 kg ai/ha (1.5, 3.0 or 6.0 lb ai/A), Snapshot 2.5TG (trifluralin + isoxaben) applied at 3.4 or 6.7 kg ai/ha (3.0 or 6.0 lb ai/A) and Ronstar 2G (oxadiazon) applied at 4.5 kg ai/ha (4.0 lb ai/A) controlled both weeds up to 60 days after treatment (DAT). Bedding plant tolerance varied with herbicide and application rate. Basil and salvia were sensitive to Snapshot (trifluralin + isoxaben) [6.7 kg ai/ha (6.0 lb ai/A)], while Ronstar (oxadiazon) [4.5 kg ai/ha (4.0 lb ai/A)] injured begonia and impatiens. Species sensitive to Dimension (dithiopyr) at 2.2 or 3.4 kg/ha (2.0 and 3.0 lb ai/A) 60 DAT were begonia, salvia, and nicotiana. Bedding plants sensitive to SWGC (pendimethalin) were celosia and salvia. Rout (oxyfluorfen + oryzalin) was injurious to most species evaluated at 6.7 kg ai/ha (6.0 lb ai/A) and in some cases at 3.4 kg ai/ha (3.0 lb ai/A). In experiments 2 and 3, shoot growth of impatiens, geranium, basil, and ageratum was not affected by any herbicide treatment. However, impatiens root growth was suppressed (30 DAT) with Dimension (dithiopyr), Snapshot (trifluralin + isoxaben), SWGC (pendimethalin) (high rate only), and Ronstar (oxadiazon). Basil root growth was suppressed 15 DAT with Dimension (dithiopyr), Snapshot (trifluralin + isoxaben), and SWGC (pendimethalin); however, all root dry weights were similar to control root dry weights at 30 DAT.

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