Hair fescue is a widespread, seed-limited perennial grass in lowbush blueberry fields. Growers rely on pronamide, an expensive and difficult herbicide to use, for hair fescue management. Recent herbicide registrations provide opportunity to reduce pronamide use, though effects of these herbicides on hair fescue suppression and seedbank reduction are not well understood. The objectives of this research were to determine (1) the effects of herbicides currently registered in lowbush blueberry on suppression of hair fescue tufts and (2) whether suppression of hair fescue with these herbicides reduces hair fescue seedbanks. Pronamide gave the most consistent reductions in flowering tuft density, though applications after both autumn pruning and autumn of the nonbearing year were required to reduce the hair fescue seedbank by >60% across sites. Nonbearing-year hexazinone applications did not control hair fescue or reduce the seedbank. Nonbearing-year terbacil applications reduced flowering tuft density, but hair fescue recovered in the bearing year, and the seedbank was not reduced. Glufosinate applications following autumn pruning or in the spring of the nonbearing year did not suppress hair fescue or reduce the seedbank. Spring nonbearing-year foramsulfuron applications, alone or after autumn or spring glufosinate applications, reduced hair fescue flowering tuft density, but hair fescue recovered in the bearing year, and the seedbank was not reduced. In contrast, autumn and spring glufosinate applications followed by spring nonbearing-year foramsulfuron applications, when combined with autumn nonbearing-year pronamide applications, reduced flowering tuft density in both the nonbearing and bearing years and reduced the hair fescue seedbank by 58% to 83% across sites. Results indicate that hair fescue seedbanks can be reduced in lowbush blueberry fields and that a reduction in pronamide use will require alternative bearing-year treatments to prevent tuft recovery and seed production.
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...
Flazasulfuron was evaluated for crop safety and efficacy on hair fescue (Festuca filiformis Pourr.) in wild blueberry (Vaccinium angustifolium Ait.) fields. Treatments consisted of flazasulfuron applied at 38 and 50 g a.i. ha−1 in fall of the bearing year and spring and fall of the non-bearing year. Industry standard fall bearing year pronamide (2240 g a.i. ha−1) and spring non-bearing year terbacil (2000 g a.i. ha−1) and foramsulfuron (35 g a.i. ha−1) applications were included for comparison. Pronamide consistently reduced flowering hair fescue tuft density in the non-bearing and bearing years across sites. Terbacil reduced flowering tuft inflorescence height in the non-bearing year, but did not reduce total or flowering tuft density in either year. Foramsulfuron reduced flowering tuft density and flowering tuft inflorescence number and height in the non-bearing year, but hair fescue recovered in the bearing year. Fall bearing year flazasulfuron applications did not reduce total or flowering tuft density or flowering tuft inflorescence number and height. In contrast, spring non-bearing year flazasulfuron applications reduced flowering tuft density and flowering tuft inflorescence number and height, though hair fescue recovered in these treatments in the bearing year. Fall non-bearing year flazasulfuron applications reduced hair fescue total tuft density, flowering tuft density, and flowering tuft inflorescence number in the bearing year. No treatments caused significant injury to wild blueberry. Flazasulfuron may contribute to improved hair fescue management in wild blueberry, and this herbicide should be evaluated further to confirm crop tolerance and identify potential use patterns with currently registered herbicides.
Summary Festuca filiformis is a common perennial grass in lowbush blueberry fields, but little is known about the general biology, seedbank characteristics, seedling recruitment or susceptibility of seedlings to currently registered herbicides. The objectives of this research were to determine (i) the presence of F. filiformis seedbanks in lowbush blueberry fields, (ii) whether F. filiformis seedbanks accumulate near the soil surface in lowbush blueberry fields, (iii) the dormancy status of fresh F. filiformis seeds, (iv) the temporal patterns of seedling recruitment in established F. filiformis populations, (v) whether F. filiformis has a vernalisation requirement for flowering in lowbush blueberry and (vi) susceptibility of F. filiformis seedlings to various herbicides currently registered in lowbush blueberry. Festuca filiformis formed a seedbank in lowbush blueberry fields, with an average of 1660 ± 272–5680 ± 1409 seedlings m−2 emerging from soil cores collected from two infested fields. Most seeds were located at the soil surface, providing opportunities for seedbank management through predation or burning. Fresh seeds lacked dormancy and readily germinated, although germination was reduced by dark conditions. New seedlings emerged in spring and autumn and required vernalisation to flower. Seedlings were susceptible to several currently registered herbicides in lowbush blueberry, although mortality rates were highest in plants treated with glufosinate, flumioxazin, glufosinate + flumioxazin and terbacil. Growers should avoid movement of seeds on machinery, and additional research should be conducted to determine the effects of registered herbicides on F. filiformis seedling recruitment under field conditions in lowbush blueberry.
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