The effect of early cropping (no removal of fruit buds the first two years) and in-row spacing (0.45 or 1.2 m) on growth and yield of `Duke', `Bluecrop', and `Elliott' northern highbush blueberries (Vaccinium corymbosum L.) was studied. Plants were grown on raised beds for four years. No yield was produced on the control plants in the planting year (year 1) and year 2. Plant growth at the start of year 3 was adversely impacted by early cropping in years 1 and 2. Early cropping reduced the dry weight of the root system, crown, and 1- to 3-year-old wood in all cultivars. `Bluecrop' plants had less total dry weight than those of `Duke' or `Elliott'. Roots accounted for 30% to 45% of the total plant dry weight depending on cultivar. Early-cropped plants had a lower percentage of fruit buds than control plants. Early cropping reduced yield 44%, 24%, and 19% in year 3, compared to control plants, in `Elliott', `Duke', and `Bluecrop', respectively. Cumulative yield (years 1 through 4) was similar between control and early cropped plants in `Bluecrop' and `Duke', whereas early cropping reduced cumulative yield in `Elliott' 20% to 40%, depending on in-row spacing. Plants spaced at 0.45 m produced 62% to 140% more yield per hectare than those spaced at 1.2 m, depending on cultivar. `Elliott' plants seemed less suited to high density planting due to their large root system.
David Bryla and Bernadine Strik
Many growers in the Pacific Northwest are planting blueberry fields at higher densities to improve yields and increase the number of berries harvested per acre in the first few years after planting. The objective of this study was to determine the effect of high-density planting on blueberry water requirements. Although close spacing reduces individual plant size, we expected that plants spaced closer together would require more irrigation per unit land area than those spaced further apart due to increased canopy coverage within rows. The study utilized a 5-year-old planting of highbush blueberry, consisting of three cultivars, `Duke', `Bluecrop', and `Elliott', planted at 0.5- and 1.2-m in-row spacings. Plant water use was calculated from changes in soil water content measured using TDR probes for shallow depths and a neutron probe and access tubes for deeper depths. Stem water potentials were also measured periodically using a pressure chamber to determine how well irrigation was meeting crop water demands throughout the season. Surprisingly, plants spaced 0.5 m apart required only slightly more water than those spaced 1.2 m apart. They did, however, require more frequent irrigations due to their smaller root systems, especially during fruit filling. Water use by each cultivar increased during fruit filling and then rapidly decreased after harvest. `Duke' required the most water among cultivars, using 5–10 mm/day from mid-May to mid-August, while `Elliott' required the least, using 3–5 mm/day.
Paula Stonerod and Bernadine Strik
All life stages of grape phylloxera [Daktulosphaira vitifoliae (Fitch) (Homoptera: Phylloxeridae)] were eradicated with a hot-water treatment (dip) of 5 minutes at 43 °C (110 °F) to warm roots, followed by a 5-minute dip at 52 °C (125 °F). Neither grafted nor nongrafted dormant grape plants were damaged by the hot-water treatment.
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.
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.
Bernadine C. Strik and Arthur Poole
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.
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.
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.
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.