75: 923-926. Photosensitization of livestock in Nova Scotia has often been attributed to St. John's wort (Hypericum perforatum L.), even though the weed generally occurs at low densities. This study's objective was to determine whether levels of hypericin, the photodynamic toxin causing photosensitization, were unusually high in Nova Scotia biotypes and whether levels increased in late spring, when photosensitization most commonly occurs. The mean hypericin content in vegetative growth of I I Nova Scotia 1L perforatum biotypes was 195 pg g-l dry wt, whereas levels in biotypes from British Columbia and Australia were at least two-and ttneefold higher, respectiveiy. HvetJ in field-collected plants were lowest in May (60 lrg g-l dry wt) and peaked in midsummer (160-280 pg g-l dry wt). In a controlled-environment study, hypericin levels increased linearly with increasing temperatures. Furthermore, hypericin levels were not affected by infection by Colletotrichum gloeosporioi'des.Thtts, the hypericin content of Nova Scotia biotypes is too low to be the cause of photosensitization in livestock.

. 2004. Response of processing carrot to metribuzin on mineral soils in Nova Scotia. Can. J. Plant Sci. 84: 669-676. Metribuzin was examined as an alternative to linuron and prometryn when prometryn-treated processed carrot in Atlantic Canada in the 1990s could not be exported to the United States, where prometryn was not registered for this crop. Field studies demonstrated that 280 g ha -1 metribuzin applied after the three-leaf crop stage resulted in only minor injury and no yield loss for both a metribuzin-tolerant (Caro-Choice) and -sensitive (Dominator) cultivar. Metribuzin applied either pre-or postemergence controlled two Matricaria species, chickweed [Stellaria media (L.) Vill.] and shepherd's-purse [Capsella bursa-pastoris (L.) Medik.], equivalent to approved prometryn and linuron treatments. Controlled environment studies were conducted to examine the effect of crop growth stage, temperature and soil pH on metribuzin injury to carrot. Differential tolerance between the two cultivars occurred only up to the three-leaf stage. Under controlled environment conditions, carrot injury to metribuzin increased threefold as soil pH increased from 6.5 to 7.4. There was little injury when metribuzin was applied postemergence under cool temperatures (15/10°C), but injury increased from 25 to 85% under 20/15°C and 30/25°C regimes. Lower temperatures and naturally low pH soils contribute to carrot tolerance to metribuzin under Nova Scotia conditions. Based on this research, metribuzin at 280 g ha -1 applied after the three-leaf stage of carrot was approved for use in the Atlantic provinces. Medik.] comme le font la prométryne et le linuron. Les auteurs ont effectué des études en milieu contrôlé pour vérifier les effets du stade de croissance, de la température et du pH du sol sur les dommages que la métribuzine cause à la carotte. La différence entre les deux cultivars au niveau de la tolérance ne se manifeste que jusqu'au stade de la troisième feuille. En milieu contrôlé, le relèvement du pH du sol de 6,5 à 7,4 triple les dommages imputables à la métribuzine. L'application du pesticide après la levée par temps frais (15/10°C) entraîne peu de dommages, mais ceux-ci augmentent de 25 % à 85 % aux températures de 20/15°C et de 30/25°C. Une température plus basse et un faible pH naturel du sol concourent à accroître la tolérance de la carotte à la métribuzine dans les conditions normales en Nouvelle-Écosse. Compte tenu de ces résultats, on a approuvé l'application de 280 g de métribuzine par hectare au stade de la troisième feuille de la carotte dans les provinces de l'Atlantique.

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 ...

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Greenhouse and field experiments were conducted to characterize a synergistic interaction between fluazifop-P and terbacil in strawberry (FragariaxananassaDuchesne). In the greenhouse, injury from foliar terbacil applications generally increased two- or more fold when 75 or 150 g/ha fluazifop-P was applied foliarly 24 h later to either a terbacil tolerant (‘Veestar’) or sensitive (‘Kent’) strawberry cultivar. Synergism also occurred when terbacil was applied as a soil drench and fluazifop-P was applied 5 d later. There was little difference in effect between tank-mixed and sequential applications made 0.5 and 20 min apart. Increased injury was also observed with intervals up to 6 d between applications in the greenhouse, and the order of herbicide application did not affect injury level. Similar results were obtained in field experiments on newly planted ‘Honeoye’ and ‘Cavendish’ strawberry. An interval of 6 d or more between terbacil and fluazifop-P application is suggested to minimize the risk of increased crop injury.