Effect of application method on dichlobenil efficacy of hair fescue (Festuca filiformis) in lowbush blueberry

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.

Hair fescue is a perennial grass weed in lowbush blueberry fields that forms dense sods and reduces yield. As a result of natural tolerance or resistance of this grass to other currently registered herbicides growers rely on preemergence (PRE) applications of pronamide and postemergence (POST) applications of the Group 2 herbicides foramsulfuron and nicosulfuron + rimsulfuron for hair fescue management. This causes repeated application of Group 2 herbicides, which is compounded by the recent registration of flazasulfuron for POST suppression of hair fescue in lowbush blueberry. Mixtures of Group 2 herbicides with the amino acid–inhibiting herbicides glyphosate (Group 9) and glufosinate (Group 10), however, can improve weed control and may delay herbicide resistance development. This research used a factorial arrangement of Group 2 herbicides (none, foramsulfuron [35 g ai ha−1], nicosulfuron + rimsulfuron [13 + 13 g ai ha−1], flazasulfuron [50 g ai ha−1]) and mixtures (none, with glyphosate [902 g ae ha−1], and with glufosinate [750 g ai ha−1]) to identify possible mixtures that improve weed control and delay resistance development. Herbicides were applied in spring nonbearing year, fall bearing year, and fall nonbearing year, with each application timing conducted as a separate experiment. Foramsulfuron and nicosulfuron + rimsulfuron were not effective as fall applications, and spring applications of these herbicides with glyphosate or glufosinate improved hair fescue suppression. Glyphosate and glufosinate were more effective as fall rather than spring applications. Flazasulfuron was effective across all application timings, although its mixture with glufosinate generally improved hair fescue suppression. Flazasulfuron + glufosinate is tentatively recommended as an effective mixture for management of spring nonbearing-year and fall bearing-year hair fescue in lowbush blueberry.

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.

Hair fescue is a 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 nonbearing-year terbacil applications (2,000 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 (Festuca filiformis Pourr.) is a tuft-forming perennial grass of concern in lowbush blueberry (Vaccinium angustifolium Ait.) as tufts form dense sods that reduce lowbush blueberry yield and inhibit harvest. Although generally tolerant to ACCase-inhibiting herbicides, injury to some Festuca spp. following clethodim applications has been reported. ACCase-inhibiting herbicides are important for non-bearing and bearing year perennial grass management in lowbush blueberry but have not been extensively evaluated for hair fescue management. The objectives of this research were to (1) determine the relative efficacy of foramsulfuron, fluazifop-P-butyl, sethoxydim, and clethodim on hair fescue, and (2) determine if foramsulfuron tank mixtures with fluazifop-P-butyl, sethoxydim, and clethodim improve hair fescue suppression. None of the herbicides evaluated caused unacceptable injury to lowbush blueberry. Foramsulfuron (35 g a.i. ha−1) reduced hair fescue total tuft density, flowering tuft density, and flowering tuft inflorescence number. Fluazifop-P-butyl (250 g a.i. ha−1) and sethoxydim (495 g a.i. ha−1) caused variable levels of visual injury to hair fescue and did not reduce total tuft density, flowering tuft density, or flowering tuft inflorescence number. Clethodim (91 g a.i. ha−1), however, caused >50% visual injury to hair fescue and reduced hair fescue total tuft density, flowering tuft density, and flowering tuft inflorescence number. Fluazifop-P-butyl and sethoxydim tank mixtures with foramsulfuron did not increase hair fescue suppression relative to foramsulfuron alone. A foramsulfuron + clethodim tank mixture provided equivalent hair fescue suppression as either herbicide applied alone. Foramsulfuron and clethodim should therefore be used in rotation rather than tank mixture to manage hair fescue in lowbush blueberry.

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 is a common perennial grass that reduces yields in lowbush blueberry fields. This grass is suppressed with nonbearing-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 nonbearing-year glufosinate applications, and spring nonbearing-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 nonbearing-year glufosinate application (0, 750 g ai ha–1), and spring nonbearing-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 nonbearing-year glufosinate applications, and spring nonbearing-year foramsulfuron applications alone provided inconsistent hair fescue suppression. Fall bearing-year glufosinate applications followed by spring nonbearing-year foramsulfuron applications, however, reduced nonbearing-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 nonbearing-year glufosinate applications or sequential spring nonbearing-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.

Red sorrel is a common herbaceous perennial weed species in lowbush blueberry fields that may be managed with acetolactate synthase (ALS)-inhibiting herbicides. Greenhouse and field experiments were established to determine the crop tolerance and potential efficacy on red sorrel of tribenuron-methyl, nicosulfuron + rimsulfuron, foramsulfuron, flazasulfuron, pyroxsulam, and halosulfuron-methyl. Ramet density of greenhouse-grown red sorrel plants established from root fragments was reduced by tribenuron-methyl, flazasulfuron, and pyroxsulam, though tribenuron-methyl and flazasulfuron were the most consistently effective herbicides under field conditions. Spring non-bearing year tribenuron-methyl and flazasulfuron applications reduced both non-bearing and bearing year total red sorrel ramet density and reduced non-bearing year red sorrel flowering ramet and seedling density without injuring lowbush blueberry. Fall non-bearing year tribenuron-methyl and flazasulfuron applications reduced bearing year red sorrel total and flowering ramet density, and this application timing should be evaluated further to improve understanding of crop injury risks. Fall bearing year tribenuron-methyl and flazasulfuron applications reduced non-bearing year red sorrel total and flowering ramet density but did not reduce seedling density. Nicosulfuron + rimsulfuron, foramsulfuron, pyroxsulam, and halosulfuron-methyl efficacy on red sorrel were inconsistent or limited, and these herbicides are not recommended for red sorrel management in lowbush blueberry.

Weed surveys provide the basis for weed management research in lowbush blueberry, but have not been conducted in Nova Scotia since 2001. Documented declines in herbicide efficacy, loss and/or acquisition of herbicide active ingredients, confirmation of herbicide-resistant weed biotypes, and documented vectoring of weed seeds by machinery necessitate a new weed survey. A total of 165 bearing year lowbush blueberry fields were surveyed from 2017 to 2019, within which approximately 211 weed species were identified. Most weed species were herbaceous perennial forbs (89 species) and woody perennials (50 species), followed by annual broadleaf (24 species) and perennial grass weeds (20 species). The remaining flora consisted of a range of ferns, biennials, sedges and rushes, and orchids. The most common weed species were red sorrel (Rumex acetosella L.), poverty oatgrass (Danthonia spicata L. Beauv.), haircap moss (Polytrichum commune Hedw.), hair fescue (Festuca filiformis Pourr.), narrow-leaved goldenrod (Euthamia graminifolia (L) Nutt.), tickle grass (Agrostis hyemalis (Walter) BSP.), woolly panicum (Panicum lanugosum Ell.), cow wheat (Melampyrum lineare Desr.), bunchberry (Cornus canadensis L.), and yellow hawkweed (Hieracium caespitosum Dumort). Increased occurrence of these weed species is likely the result of documented or observed reductions in hexazinone and terbacil efficacy, confirmation of triazine-resistant biotypes, and common occurrence of seeds of these weed species on machinery. Low crop prices have also caused reduced pronamide use, contributing to increased occurrence of hair fescue. Results are guiding future research priorities for weed management in lowbush blueberry.

Narrow-leaved goldenrod is a common creeping herbaceous perennial weed in lowbush blueberry that is difficult to manage due to limited control from pre-emergence hexazinone applications and incomplete control from post-emergence mesotrione applications. The objectives of this research were to (1) evaluate a range of summer and fall non-bearing year acetolactate synthase/ acetohydroxyacid synthase (ALS/AHAS) – inhibiting herbicide spot applications for narrow-leaved goldenrod control, and (2) evaluate broadcast applications of mesotrione applied alone or in tank mixture with foramsulfuron, nicosulfuron + rimsulfuron, flazasulfuron, and clopyralid for crop tolerance and management of narrow-leaved goldenrod in lowbush blueberry. Summer non-bearing year spot applications of glyphosate and flazasulfuron caused >90% visual injury to narrow-leaved goldenrod and reduced both non-bearing and bearing year shoot density. Spot applications of tribenuron methyl, foramsulfuron, nicosulfuron + rimsulfuron, halosulfuron, and pyroxsulam caused variable injury and did not consistently reduce narrow-leaved goldenrod shoot density. Results were similar in the fall non-bearing year experiment and they indicate that flazasulfuron could be used as an alternative to glyphosate for spot applications to narrow-leaved goldenrod due to lower crop injury from this herbicide relative to glyphosate. Broadcast mesotrione applications injured narrow-leaved goldenrod but did not reduce shoot density. Broadcast foramsulfuron, nicosulfuron + rimsulfuron, and clopyralid applications caused <60% narrow-leaved goldenrod injury and did not reduce shoot density. Tank mixture of these herbicides with mesotrione did not improve narrow-leaved goldenrod control. Broadcast flazasulfuron applications caused >60% visual injury to narrow-leaved goldenrod and reduced non-bearing year and bearing year shoot density. Flazasulfuron efficacy was reduced when applied in tank mixture with mesotrione.

Red sorrel is a common creeping herbaceous, perennial weed species in lowbush blueberry fields and reproduces asexually via ramets from creeping roots. Ramets emerge throughout the season but remain vegetative due to a vernalisation requirement for flowering. This weed may therefore be managed with fall herbicide applications, but few currently registered herbicides have been evaluated for fall red sorrel management in lowbush blueberry. The objectives of this research were to (i) determine the effect of various herbicide treatments on red sorrel shoot and root biomass in the greenhouse, (ii) determine the effect of fall bearing year herbicide applications on overwintered red sorrel ramet density in the field, (iii) determine if reduced overwintered ramet density reduces flowering ramet density in the field, and (iv) estimate the potential for red sorrel to recover from fall bearing year herbicide applications. Dicamba, tribenuron-methyl, and glufosinate reduced red sorrel shoot and root biomass in the greenhouse and reduced overwintered ramet density in the field. Clopyralid, sulfentrazone, and flumioxazin reduced shoot and root biomass in the greenhouse but exhibited limited efficacy in the field. Nicosulfuron + rimsulfuron and glyphosate were ineffective in both the greenhouse and field. Dichlobenil and pronamide reduced overwintered ramet density in the field. Reduction of overwintered ramet density did not consistently reduce flowering ramet density. Dichlobenil reduced seedling density at two sites, but no herbicide consistently reduced summer non-bearing year ramet density. Fall herbicide applications alone, therefore, do not appear to maintain red sorrel suppression in lowbush blueberry fields.

SummaryFestuca 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.

Narrowleaf goldenrod [ Euthamia graminifolia (L.) Nutt.] is the most common goldenrod species in lowbush blueberry ( Vaccinium angustifolium Aiton) fields in Nova Scotia, Canada. Knowledge of ramet emergence and phenological development of this weed is limited, and it is unknown if seedling emergence contributes to the maintenance of established populations. The objectives of this research were to 1) develop predictive growing degree day (GDD) models for E. graminifolia ramet emergence and phenological development, 2) determine if E. graminifolia forms seed banks in lowbush blueberry fields, and 3) determine if E. graminifolia seedlings emerge in lowbush blueberry fields. Cumulative E. graminifolia ramet emergence was explained as a function of GDD using a 4-parameter Weibull equation that predicted emergence to begin at 72 GDD and 90% emergence to occur at 458 GDD. Cumulative ramets at the flower bud and flowering stages was explained as a function of GDD using a 3-parameter Gompertz equation that predicted initiation of the flower bud and flowering stages at 644 and 1369 GDD, respectively, and 90% of ramets at the flower bud and flowering stages at 1522 and 2113 GDD, respectively. Cumulative E. graminifolia seedling emergence ranged from 2.4 ± 0.8 to 4 ± 1 seedlings m -2 , suggesting limited seedling emergence in lowbush blueberry fields. Seedling density from soil core samples, however, ranged from 38 ± 25 to 10,940 ± 1,456 seedlings m -2 . These results suggest that E. graminifolia forms seed banks in lowbush blueberry fields, despite the low levels of seedling emergence observed. Euthamia graminifolia seedling management should therefore be considered in current weed control programs and growers can use the developed GDD models to aid the management of established plants.

Granivory can significantly drive weed seed bank depletion in agroecosystems, but its role in weed biocontrol within commercial lowbush blueberry (Vaccinium angustifolium, Ericaceae) remains understudied. This research investigated the spatial-temporal activity and seed-feeding tendencies of Gryllus pennsylvanicus (Gryllidae), a common granivore in blueberry fields, to evaluate its weed biocontrol potential. Field and laboratory studies demonstrated that G. pennsylvanicus remained active for 14 weeks, with peak activity occurring in mid-August, aligning with the seed rain of economically significant weed species. Pitfall trap captures of G. pennsylvanicus showed no variation with distance from the field edge, indicating consistent activity across field interiors and margins. Laboratory trials showed that G. pennsylvanicus consumed seeds from nine weed species, with seed masses ranging from 0.057 to 1.9 mg. Individual crickets consumed an average of 65.5 hair fescue (Festuca filiformis) seeds per day. These findings suggest that G. pennsylvanicus may play a substantial role in reducing weed seed banks and contribute meaningfully to integrated weed management in commercial lowbush blueberry production systems.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), the spotted-wing drosophila, is an invasive pest of fruit crops, which appeared in eastern Canada in 2010. It represents a major threat to lowbush blueberry (Vaccinium angustifolium Aiton; Ericaceae) in the Saguenay-Lac-Saint-Jean region, Québec, Canada, at the northern limits of its distribution. The dynamics, overwintering capacity, population fluctuations, and damage to lowbush blueberry of D. suzukii are unknown in Saguenay-Lac-Saint-Jean. We aimed to 1) document D. suzukii abundance and phenology in lowbush blueberry in separate localities; 2) evaluate the potential of D. suzukii to overwinter and examine population dynamics over three seasons; and 3) study the spatial distribution of D. suzukii in lowbush blueberry fields with respect to forested borders. Drosophila suzukii is abundant in lowbush blueberry fields of Saguenay-Lac-Saint-Jean. In spring, D. suzukii were absent until late June, when few summer-morph females appeared. Drosophila suzukii densities started to increase regularly in August, with increasing male proportions, to culminate in fall at high levels with balanced sex ratios. Overwintering remains uncertain, D. suzukii being undetectable in spring despite intensive trapping. Appearance of diapausing winter morphs at high densities indicates that D. suzukii responds appropriately to local conditions preceding cold winter. Models of variation of D. suzukii densities and lowbush blueberry fruit infestation with distance from borders indicate that forest borders are favoured habitats over lowbush blueberry fields and the source of D. suzukii moving to some extent into lowbush blueberry fields.