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.
Hair fescue (Festuca filiformis) is a tuft-forming perennial grass that reduces yields in lowbush blueberry (Vaccinium angustifolium) fields. Nonbearing year foramsulfuron applications suppress hair fescue, but there is interest in increasing suppression through foramsulfuron use in conjunction with fall-applied herbicides. The objective of this research was to determine the main and interactive effects of fall-bearing year herbicide applications and spring-nonbearing year foramsulfuron applications on hair fescue. The experiment was a 5 × 2 factorial arrangement of fall-bearing year herbicide (none, terbacil, pronamide, glufosinate, dichlobenil) and spring-nonbearing year foramsulfuron application (0, 35 g·ha−1) arranged in a randomized complete block design at lowbush blueberry fields in Portapique and Stewiacke, Nova Scotia, Canada. Spring-nonbearing year foramsulfuron applications did not reduce total tuft density or consistently reduce flowering tuft density, flowering tuft inflorescence number, or flowering tuft seed production. Fall-bearing year pronamide applications reduced hair fescue density for the 2-year production cycle, although additional bearing year density reductions occurred when pronamide was followed by spring-nonbearing year foramsulfuron applications at Stewiacke. Fall-bearing year dichlobenil applications reduced total and flowering tuft density at each site, although reductions in flowering tuft inflorescence number and seed production were most consistent when followed by spring-nonbearing year foramsulfuron applications at Stewiacke. Suppression extended into the bearing year at each site, and dichlobenil should be examined further for hair fescue control. Fall-bearing year glufosinate applications reduced hair fescue total tuft density at each site and flowering tuft density and flowering tuft seed production at Stewiacke. Fall-bearing year glufosinate applications followed by spring-nonbearing year foramsulfuron applications also reduced nonbearing year flowering tuft inflorescence number and bearing year hair fescue seedling density at Stewiacke, indicating that this treatment may reduce hair fescue seedling recruitment at some sites. Fall-bearing year terbacil applications did not suppress hair fescue and are not recommended for hair fescue management in lowbush blueberry.
The susceptibility of poverty oat grass and rough bentgrass to foramsulfuron was assessed in greenhouse and field experiments. A dose response study was conducted in a greenhouse with treatments consisting of 0, 4.4, 8.8, 17.5, 35, 70, 140, and 280 g foramsulfuron ha−1. Field experiments were conducted using a similar dose response and also included industry standard fluazifop-P-butyl and sethoxydim applications. Foramsulfuron application rates of 4.04 ± 0.73 and 6.6 ± 1.3 g a.i. ha−1 reduced poverty oat grass biomass by 50% in the greenhouse. In contrast, 4.4 g a.i. ha−1 foramsulfuron caused >70% reduction in rough bentgrass biomass in the greenhouse. In the field, 280 g a.i. ha−1 of foramsulfuron was required to reduce poverty oat grass total and flowering tuft density and >35 g a.i. ha−1 (registered foramsulfuron rate) was required to reduce flowering tuft inflorescence number by 50%. In contrast, rough bentgrass was injured by 4.4 and 8.8 g a.i. ha−1 of foramsulfuron and total and flowering tuft density and flowering tuft inflorescence number were reduced by all other foramsulfuron rates evaluated. Foramsulfuron application rates of 13.1 ± 2.4, 10.3 ± 1.2, and 5.4 ± 0.9 g a.i. ha−1 reduced rough bentgrass total tuft density, flowering tuft density, and tuft inflorescence number, respectively, by 50%. Lowbush blueberry growers can consider foramsulfuron for postemergence management of rough bentgrass, but additional research is required to identify new herbicides for postemergence poverty oat grass management.
Hair fescue is common tuft-forming perennial grass weed that reduces yields and hinders mechanical harvest in lowbush blueberry fields. PRE terbacil applications traditionally controlled hair fescue, but currently only provide suppression in most fields. Terbacil use has not, however, been evaluated in conjunction with other currently registered herbicides in lowbush blueberry. The objective of this research was to evaluate a range of terbacil-based herbicide treatments for hair fescue management in lowbush blueberry. The experiment was conducted at three lowbush blueberry fields in Nova Scotia, Canada. Spring non-bearing year terbacil applications (2000 g ai ha-1) exhibited variable efficacy on hair fescue with reduced total tuft density at one site and reduced flowering tuft density and flowering tuft inflorescence number at two sites. Suppression was limited to the year of application only. Terbacil followed by (fb) foramsulfuron (35 g ai ha-1) did not improve suppression. A terbacil tank mixture with glufosinate (750 ai ha-1), however, reduced flowering tuft density and flowering tuft inflorescence number at each site and reduced total tuft density at one site, suggesting improved suppression with terbacil+glufosinate relative to terbacil alone. Terbacil+glufosinate fb foramsulfuron gave additional reductions in total tuft density at two sites and reduced bearing year flowering tuft density at two sites, indicating that hair fescue suppression with this herbicide combination extends into the bearing year. Although less effective than the industry standard pronamide applications, terbacil+glufosinate or terbacil+glufosinate fb foramsulfuron could be used as part of a weed management program for hair fescue in lowbush blueberry.
Hair fescue is a common perennial grass that reduces yields in lowbush blueberry fields. This grass is suppressed with non-bearing year foramsulfuron applications, though suppression may be improved through use of sequential glufosinate and foramsulfuron applications. The objective of this research was to determine the main and interactive effects of fall bearing year glufosinate applications, spring non-bearing year glufosinate applications, and spring non-bearing year foramsulfuron applications on hair fescue. The experiment was a 2 by 2 by 2 factorial arrangement of fall bearing year glufosinate application (0, 750 g ai ha-1), spring non-bearing year glufosinate application (0, 750 g ai ha-1), and spring non-bearing year foramsulfuron application (0, 35 g ai ha-1) arranged in a randomized complete block design at lowbush blueberry fields located in Parrsboro and Portapique, NS, Canada. Fall bearing year glufosinate applications, spring non-bearing year glufosinate applications, and spring non-bearing year foramsulfuron applications alone provided inconsistent hair fescue suppression. Fall bearing year glufosinate applications followed by spring non-bearing year foramsulfuron applications, however, reduced non-bearing year total tuft density, flowering tuft density, and flowering tuft inflorescence number at each site and reduced seed production at Portapique. Sequential fall bearing year and spring non-bearing year glufosinate applications or sequential spring non-bearing year glufosinate and foramsulfuron applications reduced flowering tuft density and flowering tuft inflorescence number at each site but did not consistently reduce total tuft density. Sequential herbicide treatments reduced bearing year seedling density and may therefore contribute to hair fescue seed bank management in lowbush blueberry.
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