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Bernadine C. Strik

Primocane-fruiting blackberry (Rubus L. subgenus Rubus, Watson) cultivars, Prime-Jan® and Prime-Jim®, grown only for a primocane crop, were studied for 2 years to evaluate whether this type of blackberry should be sampled at a certain stage of development or time of season to best evaluate plant nutrient status. Leaves were sampled every 2 weeks from a primocane height of ≈0.75 m in spring through fruit harvest in autumn and were analyzed to determine concentration of macro- and micronutrients. Primocanes were summer pruned at 1.4 m, by hedging to a height of 1.0 m, to induce branching, a standard commercial practice. Leaf nutrient concentration was related to stage of primocane growth and development and whether the leaves originated on the main cane or on the branches that resulted from summer pruning. Nutrient concentration of leaves sampled on the main primocane from early growth in spring until early branch growth in summer was significantly affected by cultivar, year, and week for most nutrients. When leaf sampling occurred on the older leaves of the main cane (for 4 weeks after hedging), the concentration of Ca, Mg, B, Fe, Mn, and Al increased, likely a result of the relative immobility of most of these nutrients. When samples were taken on primocane branches, leaf N, Mg, S, B (2009 only), Fe, Mn, Cu (2009 only), Zn, and Al concentrations did not differ between samples taken 6–8 weeks after summer pruning or hedging. Leaf K and Ca were more stable when sampling was done from weeks 8 to 10 (early bloom to green/early red fruit). There was a significant difference in leaf P among all weeks sampled during this period. A sample date corresponding to early green fruit stage (week 8) would thus likely provide the best compromise for assessing plant nutrient status in this crop. During this stage of development the nutrient concentrations measured for both cultivars and years, were within the present recommended nutrient sufficiency levels for other blackberry and raspberry crops for all except leaf K and P which were below current standards. The results suggest leaf sampling primocane-fruiting blackberry at the early green fruit stage (about 8 weeks after summer pruning) rather than a particular calendar date. The present leaf sufficiency range for P and K may need to be lowered for this crop. In addition, sampling cultivars separately for tissue analysis would still be advised to better manage nutrient programs.

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Bernadine C. Strik and Arthur Poole

Timing and severity of pruning in a 30-year-old commercial `McFarlin' cranberry (Vaccinium macrocarpon Ait.) bed were studied. Treatments in 1989 and 1990 consisted of early or late pruning and heavy, moderate, light, or no pruning. Yield component data were collected in Fall 1989 and 1990, just before harvest. Time of pruning did not affect yield components. In 1989, the unpruned and lightly pruned vines had a higher total plant fresh weight, fewer berries, higher berry yield, longer and more fruiting uprights, and fewer nonfruiting uprights (U,) compared with moderately or heavily pruned vines. Average length of UN and anthocyanin content of berries in 1989 were not influenced by pruning. In 1990, the effects of pruning severity were similar to 1989. In 1990, unpruned vines had a lower percent fruit set and berries contained less anthocyanin than pruned vines. Annual pruning with conventional systems in use decreases yield.

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Bernadine C. Strik and Arthur Poole

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Bernadine C. Strik and Gil Buller

Summer pruning systems were compared for ‘Prime-Jan’® primocane-fruiting blackberry (Rubus subgenus Rubus) grown in a fully closed, plastic covered tunnel in Aurora, OR. Individual canes were soft-tipped (by removing 0.10 m) or hard-tipped (removing 0.45 m) to a 1-m height on each of four dates in 2008 and 2009. On average, canes that were hard-tipped produced more branches and had more fruit/cane than soft-tipped canes. Canes that were tipped early (22–27 June) produced more fruit/cane than those tipped later (7–24 July). When canes were hard-tipped early in the season, the number of fruit/cane was increased threefold compared with soft-tipping canes early. In contrast, when plots were hedged to 1-m tall lightly (“soft” hedge removing 0.10 m) on 22–27 June or more severely (“hard” hedge, removing 0.45 m) on 29 June–2 July, using shears, there was no significant effect on yield/plot. The hard-hedge treatments may have performed better if they had been done earlier or at the same time as the soft-hedge treatments; this would only have been possible if canes had been cut back (hedged) to a shorter height than 1 m. Hard hedging, done ≈1 week later than soft hedging, delayed the fruiting season by 10–14 days. Fruit harvest continued until early to mid-November. Daily average air temperature in the closed tunnel was 2–7 °F warmer than the outside and fruit were protected from autumn rainfall. Hard-tipping individual canes, by hand, or hedging primocanes mechanically early in the season shows promise in this crop for maximizing economic returns.

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Bernadine C. Strik and David Yarborough

Blueberry production area in North American increased 30% from 1992 to 2003 to 239,818 acres (97,054 ha); most of this increase occurred in Canada. During this period, lowbush blueberry (Vaccinium angustifolium) area increased 33% and highbush 24%. In the United States, the area planted to highbush, which includes northern (V. corymbosum) and southern highbush (Vaccinium sp.) and rabbiteye (V. ashei) blueberries, increased from 48,790 acres (19,745 ha) to 55,898 acres (22,622 ha) from 1992 to 2003, a 15% increase. In 2003, the midwestern region of the U.S. accounted for 35% of the area of highbush blueberries planted. The southern, northeastern, and western regions accounted for 29%, 19%, and 13% of the planted area, respectively. Specific states in the U.S. that had considerable growth from 1992 to 2003 were California, Mississippi, North Carolina, Oregon, and Washington. In Canada, the area planted to highbush blueberries increased 105% to 11,010 acres (4456 ha). Commercial blueberry plantings in Mexico were estimated at 70 acres (28.3 ha) in 2003. In the U.S., total lowbush area increased 6% in 10 years, with Maine accounting for 97% of the area planted. In Canada, lowbush area increased 57% since 1992 with 37% and 34% of the total area present in Quebec and Nova Scotia, respectively. The blueberry industry is still projected to grow considerably in the next 5 to 10 years. Highbush blueberries in the U.S. are expected to increase in area planted by 14% and 31% in the next 5 and 10 years, respectively. In Canada, planted area of highbush blueberries is expected to increase by 22% in 5 years and 26% in 10 years. If projections are correct, planted area in Mexico will increase by almost 30-fold in 10 years. The managed area of lowbush blueberries is expected to increase by 5% to 10% over the next 10 years. Data on typical yields, types of cultivars grown, markets, proportion of machine harvest, major production problems, and changes in production practices are presented.

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Juliet Mann and Bernadine C. Strik

Mature `Kotata' and `Marion' trailing blackberry plants were studied in 1994. In `Kotata', canes were subjected to 0%, 25%, 50%, 75%, or 100% primary bud removal in Feb. 1994. In `Marion' 0, 55, or 100 primary buds were removed per dm2 from fruiting sections (panels). Primary bud removal did not subsequently affect yield per cane or per dm2 in either cultivar. Yield compensation occurred through production of secondary laterals, which were as fruitful as primary laterals.

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Bernadine C. Strik and Ellen Thompson

Primocane-fruiting blackberries produce fruit on current-season canes (primocanes) and second-season canes (floricanes), if desired. Primocane-fruiting blackberries are likely adapted to a diverse range of climates, particularly because cold hardiness is not an issue when plants are grown for a primocane crop only. The floricane crop of ‘Prime-Jan’® and ‘Prime-Jim’® is from 3 June to 6 July in Arkansas and 30 June to 22 Aug. in Oregon, thus overlapping with other fresh market blackberries. However, although the primocane crop overlaps with the semierect cultivar Chester Thornless, the fruiting season of the primocane-fruiting types is longer. Harvest on primocanes began 17 July and mid-August in Arkansas and Oregon, respectively. The primocanes of ‘Prime-Jan’ and ‘Prime-Jim’ tend to branch naturally, producing a couple of branches near the base. However, soft-tipping primocanes at 1 m early in the season increased branch and flower number, resulting in a threefold yield increase compared with untipped canes. Yield and berry size in Oregon has been from 1.8 to 5.2 t·ha−1, depending on primocane management treatment, and 5.2 to 7.4 g, respectively. However, yield would have been much higher if all fruit could have been harvested as would be possible under protected culture. Our research to date indicates that primocane-fruiting blackberry can be easily manipulated to adjust harvest time. Remowing primocanes to create a delayed flush of growth will delay harvest. Rowcovers or tunnels that increase temperature will advance primocane growth and harvest. Soft-tipping height and frequency can affect cane architecture and season. Management techniques along with new genotypes of primocane-fruiting blackberry will have a great impact on blackberry production worldwide.

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Bernadine C. Strik, Neil Bell and Gina Koskel

`Redcrest' plants were renovated at 2, 4, 6, 8, or 10 weeks after harvest (WAH) from July 1 to Aug 26, 1992 and July 7 to Sept 1, 1993, plus an unrenovated control. Data on fall yield, maximum cold hardiness, and summer yield and berry weight were collected. For maximum cold hardiness, crowns were subjected to controlled freezing (-8, -11, -14, -17 or -20°C) and then evaluated by oxidative browning. Fall yield in 1993 was greater than in 1992. In 1992, fall yield was comparable for all renovation dates except the latest, 10 WAH. Unrenovated plants tended to have a lower fall yield than renovated plants. In 1993, plants renovated 2, 4, or 6 WAH had higher yields than control or late-renovated plants. Fall yield was not correlated with summer yield in 1993. Plants renovated 4 WAH had a higher summer yield in 1993 than unrenovated plants or those renovated at other times, which all had similar yields. Date of renovation had no effect on berry weight or percent fruit rot. Unrenovated plants and those renovated 2 or 4 WAH were hardier in winter 1992/93 than those renovated later.

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Jessica M. Cortell and Bernadine C. Strik

Treatments consisting of 0, 4, 8, or 12 floricanes were established in March 1993. An additional treatment was set up with zero floricanes and early primocane pruning. Starting in April and continuing through early November, weekly primocane measurements were taken including: number of nodes, number of primocanes, number of branch canes, length of primocanes, and length of branch canes. Additional plants in each treatment were harvested in August to assess total biomass partitioning. The zero floricane treatment had a significant increase in the number and length of both primocanes and branches. Primocanes grown without competition from floricanes had a 65 % increase in primocane dry weight. Primocane pruning resulted in significantly shorter internodes, an increase in branch dry weight, and a decrease in total length of the primocanes. The increase in total primocane biomass with removal of the floricanes should contribute to higher yields the following season.

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Amanda J. Vance and Bernadine C. Strik

Fresh market blueberry (Vaccinium sp.) sales require high-quality, firm fruit with no significant defects. A new phospholipid biofilm product was developed to reduce splitting and increase firmness when applied directly to blueberry fruit. Two trials were undertaken to test the effects of the biofilm using various application timings and methods. In highbush blueberry cultivar Elliott (Vaccinium corymbosum), four treatments included: 1) rate and timing on the current product label (5- to 10-mm berry size, 10% to 20% color change, and between the first and second harvests), 2) addition of a preharvest timing (5- to 10-mm berry size, 10% to 20% color change, and 7 to 10 days preharvest); 3) starting applications later (10% to 20% color change, 7 to 10 days preharvest, and between the first and second harvests), and 4) a water-sprayed control. Biofilm was applied at a rate of 2 qt/acre for all applications. In highbush blueberry cultivar Legacy (Vaccinium corymbosum × Vaccinium sp.), the same volume of biofilm was applied via an airblast sprayer or through an overhead sprinkler system typically used for chemigation and compared with a water-sprayed control. Data collected included yield (in ‘Elliott’), berry weight, firmness, skin toughness, total soluble solids (TSS), weight loss during storage, percent splitting (in ‘Legacy’), and a visual rating, evaluated on the day of harvest and about 14 and 28 days postharvest. There were no visual defects caused by application of biofilm. Compared with the controls in either study, biofilm had no consistent impact on fruit quality, firmness, shelf life, yield in ‘Elliott’, or splitting in ‘Legacy’.