Potential Role of Sequential Glufosinate and Foramsulfuron Applications for Management of Fescues (Festucaspp.) in Wild Blueberry

Abstract

Sheep and hair fescue are perennial, tuft forming grasses that spread by seed and form dense sods in wild blueberry fields. These sods compete with the crop for resources and hinder harvest. Field and greenhouse studies were conducted in 2015 to evaluate 1) the effect of sequential glufosinate and foramsulfuron applications on suppression of fescues in the greenhouse and field, and 2) efficacy of glufosinate and foramsulfuron on fescue seedlings when applied at 2, 4, 6, and 8 wk after seedling emergence in the greenhouse. Glufosinate applications at 750 and 1,005 g ai ha −1 followed by foramsulfuron application at 35 g ai ha −1 reduced fescue leaf number and biomass relative to foramsulfuron application alone in the greenhouse. In the field study, fescue flowering tuft density, tuft inflorescence height, seed production, and seed viability were reduced by foramsulfuron alone, but there was a trend towards lower seed production and tuft height when fescues were treated with glufosinate at 1,005 g ha −1 followed by foramsulfuron. Foramsulfuron caused low seedling mortality at all application timings evaluated, but glufosinate caused >90% mortality in seedlings when applied at 2, 4, 6, or 8 wk after seedling emergence. Our results suggest that sequential applications of these herbicides are less effective under field conditions relative to results obtained in the greenhouse, though burndown glufosinate applications may have a role in reducing fescue seedling recruitment. Additional research should be conducted to determine the effect of early spring and autumn glufosinate applications on fescue seedling recruitment and suppression of established fescue tufts with subsequent foramsulfuron applications. Nomenclature: Foramsulfuron; glufosinate; sheep fescue; Festuca ovina L. FESOV; hair fescue, Festuca filiformis Pourret FESTE; lowbush blueberry, Vaccinium angustifolium Aiton. Key words: Perennial crop, perennial grass, burndown herbicide, sequential herbicide.Festuca ovina y Festuca filiformis son gramíneas perennes que forman espigas, que se son dispersadas por semilla y que forman céspedes densos en campos de arándano silvestre. Estos céspedes compiten con el cultivo por recursos y dificultan la cosecha. En 2015 se realizaron estudios de campo y de invernadero para evaluar 1) el efecto de aplicaciones secuenciales de glufosinate y foramsulfuron sobre la supresión de plántulas de Festuca spp. cuando se aplicaron a 2, 4, 6, y 8 semanas después de la emergencia de las plántulas en el invernadero. Aplicaciones de glufosinate a 750 y 1,005 g ai ha −1 seguidas por una aplicación de foramsulfuron a 35 g ai ha −1 redujeron el número de hojas y la biomasa de Festuca spp. en relación con aplicaciones de sólo foramsulfuron en el invernadero. En el estudio de campo, la densidad de inflorescencias, la altura de la inflorescencia, la producción de semilla, y la viabilidad de la semilla fueron reducidas con la aplicación de foramsulfuron solo, pero hubo una tendencia hacia una menor producción de semilla y de altura de infloresc...

Determination of Festuca filiformis seedbank characteristics, seedling emergence and herbicide susceptibility to aid management in lowbush blueberry (Vaccinium angustifolium)

“…Festuca filiformis seeds are also susceptible to heat (White & Boyd, ), and although burn pruning does not consistently reduce F. filiformis density (Penney et al ., ), the location of most seeds on the soil surface suggests that burn pruning may be an effective method of seedbank management for these grasses. It is unclear why seedling density, but not seed density, was affected by site, although viability of F. filiformis seeds is variable (White & Kumar, ) and the difference in seedling density at each site may simply be reflective of this characteristic of seeds of this weed in lowbush blueberry fields.…”

“…), future research should evaluate the effects of spring terbacil applications, spring or autumn glufosinate applications, or autumn flumioxazin + glufosinate tank mixture applications on F. filiformis seedling recruitment under field conditions. Although foramsulfuron did not cause high seedling mortality under experimental conditions, this herbicide stunts established tufts (Yarborough & Cote, ) and reduces flowering tuft density, tuft inflorescence number and seed production under field conditions in the non‐bearing year (White & Kumar, ). Spring foramsulfuron applications in the non‐bearing year may therefore reduce autumn non‐bearing year and spring bearing year seedling populations due to reduced seed rain and seedbank replenishment, and this should be investigated further under field conditions.…”

“…This was maintained at a constant temperature of 21°C with an 8 h photoperiod provided by fluorescent bulbs providing a light intensity of 23 μmol m −2 s −1 . Seeds were soaked in distilled water for 10 min prior to use in the germination tests to verify the presence of an embryo within the seed (White & Kumar, ). Seeds with visible embryos were considered viable, and 10 replications of 50 viable seeds were used for the light and dark germination tests.…”

“…Management of tufted fescues currently relies primarily on pre‐emergence applications of the herbicide propyzamide due to the limited efficacy of alternative herbicides (Yarborough & Cote, ; White & Kumar, ). Although effective, the lack of alternative control options limits the long‐term sustainability of propyzamide as a management tool, as exclusive reliance on this product increases the likelihood of selection for herbicide resistance (Ross & Lembi, ).…”

“…In particular, current lack of emphasis on seedling recruitment and seedling management is probably resulting in reduced efficacy of current control measures. Festuca filiformis seedlings are susceptible to some herbicides currently registered in lowbush blueberry (White & Kumar, ), but general evaluations to identify optimum products or product combinations are lacking. Growers are therefore lacking both basic biological data and practical efficacy data, to implement seedling management as a component of an overall fescue management plan.…”