Turfgrass injury from triazines has limited the use of photosystem II (PS II) inhibitors for weed control in seashore paspalum. Amicarbazone is a new PS II inhibitor with potential safety in seashore paspalum, but the effects of application timing on turf tolerance has received limited investigation. Field experiments were conducted in Griffin, GA to evaluate the tolerance of ‘Sea Isle 1’ seashore paspalum to amicarbazone applications in winter, spring, and summer. Seashore paspalum had minimal injury (< 5%) from amicarbazone treatments (98, 196, and 392 g ai ha⁻¹) applied for annual bluegrass control in winter and spring. By 6 wk after treatment (WAT), amicarbazone at 392 g ha⁻¹ provided 78 and 90% annual bluegrass control in 2013 and 2014, respectively, and was similar to pronamide at 1,680 g ai ha⁻¹. Amicarbazone at 196 g ha⁻¹ provided 71% control of annual bluegrass in 2014, but control was poor (< 70%) in 2013. Sequential amicarbazone applications at 98 g ha⁻¹ provided poor control in both years by 6 WAT. From six amicarbazone rates (up to 984 g ha⁻¹) applied in summer, seashore paspalum required 510 and < 123 g ha⁻¹ for 20% turfgrass injury (I₂₀) and 20% clipping reduction (CR₂₀), respectively, whereas I₂₀ and CR₂₀ measured > 984 g ha⁻¹ for ‘Tifway’ bermudagrass. Overall, amicarbazone may be safely applied to seashore paspalum in winter, spring, and summer at rates and regimens evaluated. However, seashore paspalum may exhibit shoot growth inhibition up to 4 WAT, suggesting that end users should be cautious when using amicarbazone during active growth in summer.

Nomenclature: Annual bluegrass, Poa annua L.; bermudagrass, Cynodon dactylon × C. transvaalensis Burtt-Davy ‘Tifway’; seashore paspalum, Paspalum vaginatum Sw. ‘Sea Isle 1’.

El daño al césped causado por triazines ha limitado el uso de inhibidores del fotosistema II (PSII) para el control de malezas en Paspalum vaginatum. Amicarbazone es un inhibidor PSII nuevo con potencial de ser seguro en P. vaginatum, pero los efectos del momento de aplicación sobre la tolerancia del césped han sido investigados poco. Se realizaron experimentos de campo en Griffin, Georgia para evaluar la tolerancia de P. vaginatum 'Sea Isle 1′ a aplicaciones de amicarbazone en el invierno, la primavera, y el verano. P. vaginatum tuvo daño mínimo (<5%) con tratamientos de amicarbazone (98, 196, y 392 g ai ha⁻¹) aplicados para el control de Poa annua en el invierno y la primavera. A 6 semanas después del tratamiento (WAT), amicarbazone a 392 g ha⁻¹ brindó 78 y 90% de control de P. annua en 2013 y 2014, respectivamente, y fue similar a pronamide a 1,680 g ai ha⁻¹. Amicarbazone a 196 g ha⁻¹ brindó 71% de control de P. annua en 2014, pero el control fue pobre (<70%) en 2013. Aplicaciones secuenciales de amicarbazone a 98 g ha⁻¹ brindaron control pobre en ambos años a 6 WAT. A partir de seis dosis de amicarbazone (hasta 984 g ha⁻¹) aplicadas en el verano, P. vaginatum requirió 510 y <123 g ha⁻¹ para causar 20% de daño al césped (I₂₀) y 20% de reducción en los residuos de corta o clippings (CR₂₀), respectivamente, mientras I₂₀ y CR₂₀ fue >984 g ha⁻¹ para Cynodon dactylon × C. transvaalensis Burtt-Davy 'Tifway'. En general, amicarbazone puede ser aplicado en forma segura a