Response of lowbush blueberry (Vaccinium angustifolium) to hexazinone applied early in the fruiting year

Abstract

The wild lowbush blueberry (Vaccinium angustifolium Ait.) is economically the most important fruit crop of Atlantic Canada and the State of Maine. Some 70 000 to 90 000 t of fruit are produced annually on about 53 000 ha. Commercial blueberry fields have been developed from cleared forest or abandoned farmland where the lowbush blueberry is an early seral species. The crop is managed on a 2-yr production cycle. In the first year, plants are pruned by either burning or flail mowing, which promotes new shoot growth from rhizomes and increases flower bud development. In the second year, the crop blooms and produces fruit (Yarborough 1997).Weeds have always been a major production problem. Weeds of lowbush blueberry fields are mostly members of the native flora that are also promoted by the 2-yr crop cycle and include a wide range of perennial herbaceous and woody species that typically reflect the original flora of the field (Jensen 1985). Prior to 1980, weed control mainly involved cutting, burning, and directed spot sprays or rollerwiper applications of non-selective growth regulator herbicides for woody weed control. This changed in the early 1980s with the introduction of the broad spectrum s-triazinone, hexazinone. When applied pre-emergently in the spring after the pruning operation, but before the emergence of the new blueberry growth, 1.5 to 2.0 kg ha -1 hexazinone provided selective control of most grasses and sedges, and many of the common herbaceous broadleaf and woody weeds found in blueberry fields at that time (Jensen 1985). This pre-emergence application is also the most effective in controlling weeds, while later postemergence applications cause serious foliar damage to the crop (Jensen 1985). Weed control in the prune year increases blueberry stem density, numbers of flower buds per stem, and fruit yield (Eaton 1994;Jensen 1986;Yarborough et al. 1986). Applications at other times do not generally affect potential yields directly because these applications do not affect yield parameters.Initial applications of 1.5 to 2.0 kg ha -1 hexazinone to a blueberry field generally results in excellent residual weed control over the 2-yr crop cycle. Subsequently, rates are reduced to control mainly germinating weeds. Rates are also reduced in response to increasing concerns about erosion on vegetation-free soils and potential ground/water contamination. However, hexazinone persistence in blueberry field soils is relatively short. Less than 10% of applied hexazinone was recovered in the upper profile (0-45cm) of soils 2 mo after application and year-to-year carryover was <5% (Jensen and Kimball 1987). Hence, a number of native grass and herbaceous broadleaf weed species, e.g., Danthonia spicata, Rumex acetosella, and Solidago spp., either recover from low herbicide rates or re-establish from seed. These weeds impede harvesting and reduce marketable yield in the fruiting year. Earlier prune-year studies (Jensen 1985) had demonstrated that good control of some of these weeds could be obtained with only 1.0 kg ha ...

Hexazinone and Fertilizer Impacts on Sheep Sorrel (Rumex acetosella) in Wild Blueberry

“…Where vegetative-year hexazinone applications reduced sheep sorrel populations, applying hexazinone in the fruiting year further reduced sheep sorrel densities by about half (Table 1). This is similar to the findings of Jensen and Specht (2002), where 94% control of sheep sorrel was obtained with 1.0 kg ai ha 21 hexazinone.…”

Growing Degree-day Models for Predicting Lowbush Blueberry (Vaccinium angustifolium Ait.) Ramet Emergence, Tip Dieback, and Flowering in Nova Scotia, Canada

“…Predictions from our proposed Weibull model were in close agreement with field observations ( Fig. 5E-F) and can be used to facilitate disease monitoring at early bloom and improve timing of bearing-year hexazinone applications (Delbridge et al, 2011;Jensen, 2002). When combined with the results from the Gaussian model ( Fig.…”

The Impacts of Fertilizer and Hexazinone on Sheep Sorrel (Rumex acetosella) Growth Patterns in Lowbush Blueberry Fields

“…Hexazinone controls sheep sorrel populations, but efficacy varies between sites and years (Kennedy 2009, Kennedy et al 2010. Hexazinone also can be applied POST at a rate of 1.0 kg ai ha 21 in the spring of the crop year if susceptible weeds pose a problem to crop yields (Jensen and Specht 2002). Applications must be conducted no later than the early bloom stage (DuPont 2009;Jensen and Specht 2002) as applications after this date will cause serious foliar damage to the blueberry plant resulting in significant crop damage and yield loss (Jensen 1985;Jensen and Specht 2002).…”

“…Hexazinone also can be applied POST at a rate of 1.0 kg ai ha 21 in the spring of the crop year if susceptible weeds pose a problem to crop yields (Jensen and Specht 2002). Applications must be conducted no later than the early bloom stage (DuPont 2009;Jensen and Specht 2002) as applications after this date will cause serious foliar damage to the blueberry plant resulting in significant crop damage and yield loss (Jensen 1985;Jensen and Specht 2002). During the 2-yr production cycle, blueberry farmers also add fertilizers to improve blueberry yields and promote growth (Jeliazkova and Percival 2003).…”