OSU BLUEBERRY SCHOOL
March 16-17, 2015
held at
Oregon State University, Corvallis, Oregon
This two-day blueberry “school” was organized for new and experienced blueberry growers,
farm managers, crew leaders, advisors, packers/shippers, and consultants. Experts from Oregon
State University, USDA Agricultural Research Service, Washington State University, and the
blueberry industry were asked to address key issues of where the blueberry market is going; how
you might be more successful in tight labor or volume markets; which cultivars are easiest to
grow and are in most demand; how to establish new acreage using cutting-edge methods;
projected costs and the resources available to growers for selecting new planting sites; how to
best manage existing acreage to maximize returns of high-quality fruit; provide basic information
on blueberry plant physiology to help growers minimize environmental stresses and improve
yield potential; nutrient management programs for optimal growth and quality; irrigation and
fertigation practices for higher quality and better efficiency; use of organic amendments and
mulches; planning for and improving machine harvest efficiency; pruning for hand or machine
harvest (where can you cut corners….or not), maximizing pollination for good fruit and seed set;
overviews of the most important blueberry viruses, diseases, insects, weeds, and vertebrate pests;
and tools for good pest management. Information throughout the program addresses the needs of
conventional, transitional, and organic growers. Simultaneous interpretation to Spanish has been
provided. This proceedings book contains information provided on these topics by each speaker
and co-authors. The thumb drive provided in the registration packet for each attendee includes a
copy of each presentation. Thank you for attending. It is our sincere wish that this will be a very
useful meeting and that you find the accompanying materials a valuable reference! –
Bernadine Strik, Professor and Extension Berry Crops Specialist, OSU and the members of the
organizing committee
Organizing Committee
Bernadine Strik, Chair, Oregon State University (OSU)
Wei Yang, OSU. Co-chair (sponsorship coordinator), OSU
Donna Williams, Rachel Williams & team at OSU Conference Services
Dave Bryla, USDA-ARS HCRU
Chad Finn, USDA-ARS HCRU
Vaughn Walton - OSU
Steve Castagnoli - OSU
Steve Renquist - OSU
Bryan Ostlund – Oregon Blueberry Commission
Eric Pond - industry
Jon Umble – industry
Derek Peacock - industry
Steve Erickson - industry
Nancy Jensen - industry
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Table of Contents
OSU Blueberry School
Title
Authors
Characteristics of production regions in the Pacific
Northwest
Lisa DeVetter, Pat Jones, Bernadine
Strik, Kathie Dello
1
Markets - what's the future for fresh, processed, and
organic markets? Things you MUST think about before
starting or expanding production
Rod Cook, Derek Peacock, Jeff
Malensky, David Granatstein
9
Cultivar choices- Tried and true to brand new
Chad Finn and Bernadine Strik
15
Economics of production – resources
Bernadine Strik and David Granatstein
29
Resources available for selecting a good blueberry site
Wei Q. Yang
37
Site selection and establishment of a blueberry field
Wei Q. Yang and Bernadine Strik
41
Organic soil amendments and mulches for blueberry:
the good, the bad and the ugly
Dan Sullivan (OSU)
47
On-farm irrigation system design and operation
David Bryla
53
Blueberry plant physiology - why it's important to
understand the plant to manage it well
Bernadine Strik
57
Irrigation scheduling: when, where, and how much?
David Bryla
63
Pruning - impact of plant age, cultivar, and harvest
method
Bernadine Strik
69
Harvesting - hand vs. machine
Bernadine Strik (moderator); Paul
Norris (Norris Farms); Frank Brown
(Littau Harvesters (Inc.); Doug
Krahmer (Berries Northwest)
75
Nutrient management of blueberry -- assessing plant
nutrient needs and designing good fertilizer programs
Bernadine Strik and David Bryla
79
Maximizing pollination in blueberry
Ramesh Sagili, Carolyn Breece, John
Borden
95
Blueberry viruses present in the Pacific Northwest and
suggestions for their management
Robert Martin
99
Blueberry bacterial and fungal diseases
Jay Pscheidt and Jerry Weiland
107
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Page
Title
Authors
Page
Weed management for blueberry fields in the Pacific
Northwest
Tim Miller
115
Getting hit high and low: Options for managing bird
and vole damage
Dana Sanchez (OSU
125
Management of arthropods, insect, and plant-parasitic
nematodes in blueberries
Vaughn Walton,Nik Wiman, Inga
Zasada, Joe DeFrancesco, Daniel
Dalton, Amy Dreves, Jana Lee, Lynell
Tanigoshi, Wei Yang
129
iii
Site selection and establishment of a blueberry field
1
Wei Q. Yang1 and Bernadine Strik2
North Willamette Research & Extension Center, Oregon State University
2
Department of Horticulture, OSU
Site selection
Selecting a potential site for a blueberry plantation is one of the most important decisions a
grower can make. Slope, elevation, drainage, soil type, microclimate, and surrounding vegetation
are all important factors to consider when choosing a site. With the rapid expansion of blueberry
production in the northwest, blueberry plantings have been established in some less than
desirable locations which either lead to reduced yield or increased management costs. The
question of what constitutes the best blueberry site is asked often, however, there isn’t always a
right answer.
Slope, elevation, and surrounding vegetation greatly affect site microclimate. In sloped ground,
leaving enough clear easement at the base of the slope will allow cold air to drain away in frosty
weather conditions because low-elevation areas on sloped ground often accumulate the most cold
air. This can be especially critical during the spring when blossoms can be damaged by frost.
Good air circulation also reduces fungal disease pressure such as gray mold (Botrytis spp.) and
mummy berry (Monilinia vaccinii-corymbosi). Slopes with a southern exposure can be 5 to 8°F
warmer during the spring and fall, thus encouraging earlier bud development (and potential for
spring frost injury) and earlier berry ripening. However, these sites are often warmer than a
northern facing slope, perhaps reducing the risk of frost injury.
Slope also should be considered if the field is to be harvested mechanically. The newest overthe-row harvesters can travel across steep slopes because they have automatic leveling. However,
excessive slope will interfere with the operation of the catcher plates on the picking unit,
resulting in more fruit loss and may be hazardous to the machine operator if the machine can tip
over. If the rows are to be oriented up and down the slope, slopes of greater than 10 percent (1
foot rise for every 10 feet) should be avoided for plantings to be machine harvested, as berries
will tend to roll to the back end of the picking unit and will not be collected properly.
Sites at high elevations often experience damaging wind and rain or snow from storms. Plants
should be trellised to prevent weather related damage. The use of windbreaks is recommended,
and they should be porous so as to slow wind speed by approximately 50 percent. Well-managed
windbreaks will reduce excessive water loss from the soil in the summer and will improve
pollination during bloom as bees will be more prone to exit their hives. A good discussion of
windbreak species and their installation and maintenance can be found in Trees Against the
Wind, PNW 5.
Surrounding vegetation should be considered when selecting a site. The perimeter of a site may
not only host wildlife (e.g. deer and birds) but it may also provide a refuge for spotted wing
drosophila (SWD), which is a serious insect pest of blueberries. Localized SWD hotspots have
been found in trees and vegetation adjacent to blueberry plantings because of the presence of
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non-crop hosts for SWD in the perimeter of a site. The characteristics of non-crop habitat for
SWD include high plant diversity, close proximity to alternative hosts (potential oviposition
sites), riparian habitat, landscape refuge and areas with a high degree of canopy cover.
Recognizing these high-risk areas in trees and adjacent vegetation of a blueberry planting is
important to employing management strategies. A good discussion about SWD non-crop hosts
can be found in Protecting Garden Fruits From Spotted Wing Drosophila, EM 9026.
Sites in eastern Oregon may not have the ideal blueberry soil, however, the unique climate
conditions and market niche warrant blueberry plantings, albeit often requiring higher inputs.
Soils and drainage
Blueberries do best in soils with a pH of 4.5 to 5.5. If the soil pH is too high, iron chlorosis
symptoms develop on leaves (green veins, interveinal yellowing) and plants will not grow well.
In areas west of the Cascades, the native soil pH usually is acidic unless there has been a
previous crop that has required the addition of agricultural lime. Soils east of the Cascades must
be acidified to grow blueberries and acidified irrigation water is typically used during production
(see nutrient and irrigation management presentations).
Soils in eastern Oregon are typically calcareous or sodic. Calcareous soils contain calcium
carbonate and generally have a pH of more than 7.0. Sodic, or sodium-affected, soils have a soil
pH of 8.4 to 10.0 or even higher and are not recommended for growing blueberries. These soils
need to be amended to increase soil organic matter and adjust soil pH to desirable levels. For
discussions of how to acidify soils east of the Cascades, please consult OSU Extension
Publication EC 1560.
Soil drainage is critical when selecting a site. The best blueberry soil type is one in which
precipitation drains through completely following a rain event, yet sufficient moisture is held
during the dry period to support good plant growth. Silt and sandy loam soils are best as they
generally have good water infiltration capacities and moderate water-holding capacities, and
therefore good drainage. Heavy and clay soil types have poor drainage and need to be amended
with organic matter to increase infiltration rates and drainage capacity. At least 5% organic
matter in the soil is recommended. See the separate presentation on soil amendments.
A quick way to determine soil drainage is to dig a 12 inch diameter hole to 1 foot deep and fill
the hole with water. If the water drains away after 3 hours, the soil has good drainage. If the
water does not drain completely after 8 hours, soil drainage is poor. Poor drainage affects plant
growth similarly to repeated flooding. Phytophthora root rot of blueberry often occurs in poorly
drained soils. Highbush blueberries can tolerate a maximum of 4 consecutive days of flooding
during the winter and 1 day in the spring or fall.
For sites where the water table is high, agricultural drain tile can be installed in fields with
problem drainage spots. The best blueberry sites are those that have a water table at least 18
inches below the soil surface. Plastic drain tile usually is set 3 to 5 ft below the soil surface and
must be installed prior to planting a field because the drain lines usually do not parallel plant
rows. To overcome problems with a high water table and/or increase drainage, planting rows can
be mounded to form raised-beds (see below).
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After a site is selected, a soil test is needed to determine whether soil modifications are
necessary. Any soil modifications should be planned at least one year prior to planting (see the
nutrient management presentation). All perennial weeds, including quackgrass, Canada thistle,
field bindweed, curly dock, horsetail rush, blackberries, and others, need to be totally eliminated.
Fall plowing prior to spring planting is not adequate. A broadcast application of herbicide
followed by plowing and disking will kill many perennial weeds (see the weed management
presentation).
Once the field is cleared and drainage problems have been addressed (e.g. through installation of
drainage tiles), a cover crop can be sown to protect the ground from weed invasion prior to
planting. Annual cover crop choices include cereal grains such as wheat, barley, oats, or cereal
rye (100 to 120 lb seeding rate/acre) and annual ryegrass (15 to 30 lb/acre). Cover crops can be
turned under by cultivation before building raised beds for planting in the fall or spring. Refer to
“Estimating Plant-Available Nitrogen from Cover Crops”, PNW 636; it is not advantageous to
have very high nitrogen in blueberry soils prior to planting as this may lead to late growth in the
planting year – this may be of particularly concern in growing regions east of the Cascade
Mountains due to potential for winter or cold damage.
Raised beds
In an 8-year study, plants growing on raised beds had a cumulative yield 23% greater than those
grown on flat ground (Strik et al., in progress). In addition, raised beds improve machine harvest
efficiency since the catcher plates fit lower down on the crown where it is more narrow. If the
field is to be harvested mechanically, make sure the width of the raised bed is no wider than the
“boot” (lower entrance) of the machine harvester. A typical raised bed is 12-18 inches high and 4
ft wide at ground level. Prior to forming the raised beds with a bed shaper, incorporate any
amendments and nutrients (see nutrient management and organic amendment presentations).
Make the raised beds just prior to planting, after the soil has been modified. Raised bed rows are
usually spaced 10 or 11 ft apart from row centers. While a 10 ft row spacing is presently most
common, 11 ft row spacings are being used in some new plantings to accommodate spray
equipment for anticipated SWD control when plantings are mature and to provide more room to
accommodate machine harvest.
Planting
Order plants well in advance of planting as the most some cultivars are in high demand (see
cultivar presentation). While many older plantings were established at an in-row spacing of 4 to
5 ft, a 10-year study at Oregon State University (Strik and Buller, 2002) yield of blueberry was
considerably greater during the plant establishment years (year 2 through 6) when plants were
established at 1.5 or 3 ft in the row. Not all cultivars are adapted to very high density planting
(Strik, personal observation) and plants at 1.5 ft in the row are very difficult to prune. Since the
study, the most common in-row plant spacing in new plants are 2.5 to 3 ft (1,742 and 1,452
plants/acre at 10 ft row spacing, respectively). More vigorous cultivas such as ‘Legacy’ should
be planted at 3 ft in the row (Strik, personal observation). Rabbiteye blueberry should be spaced
at 3.5 to 4 ft in the row. For intended machine harvest, include 25 to 30 ft of space at the ends of
43
rows (headland) to accommodate turning of the machine harvester. In addition, blocks or rows
should not be too long so that fruit can be unloaded more easily.
Planting in the spring or fall is acceptable in most production regions. However, spring planting
is best in the colder regions of the PNW. While many plant sizes are available from commercial
nurseries, plants with 3 or more strong whips (see physiology presentation and pruning) that are
at least 18 inches tall, generally in one-gallon pots, establish quickly and better tolerate adverse
weather conditions. Be aware that use of smaller-sized nursery plants may lead to more difficulty
in management and a delayed fruit production (longer establishment period). Plants must be
pruned to prevent fruit production in the planting year (year 1) and pruned to greatly limit fruit
production in year 2 to encourage good root and vegetative growth (see pruning presentation).
Plants should be irrigated and fertilized carefully – see irrigation design and nutrition
presentations.
A grass is typically seeded between rows and is maintained annually by mowing.
Some growers in windy regions have used grow tubes to aid in planting establishment. These
also reduce plant damage from contact herbicides and herbivory. When tubes are used in regions
without wind pressure (e.g. most areas in the Willamette Valley), plants in tubes may initially
have a larger top growth, but they also have less root growth than plants without tubes (Strik et
al., 2014). However, plants “catch up” after a few years showing no difference in growth
between tubes and un-tubed plants. Thus, tubes should only be used on windy sites – in such
cases, only use a tube material that lets some light through and tie the tubes to trellis wires and
stake them well to prevent the plant and tube rotating in the wind (this weakens the crown).
Mulching
While there are some plantings in the PNW that have bare soil within the row (no mulch), use of
an organic material as a mulch (most commonly sawdust) is most common. In new plantings,
weed mat (porous, polyethylene landscape cover) is becoming very common in conventional and
organic plantings. In an 8-year study in organic production systems, weed mat performed equally
well as sawdust or as yard debris compost plus sawdust as a mulch for yield and fruit quality
(Strik et al., in progress). However, addition of compost to the mulch greatly increased weed
pressure and weed control costs. While weed mat nearly offers complete weed control, the edges
of the grass cover crop between rows need to be managed to prevent encroachment on the weed
mat – organic growers often do this using a string trimmer. In addition, weed mat increases soil
temperature and may increase the top to root ratio – this has made irrigation management more
difficult, especially on raised beds. Finally, use of weed mat has reduced soil organic matter over
the 8-year study. We thus recommend a zippered weed mat that can be opened. This allows
addition of organic matter and any granular fertilizers in conventional as well as organic systems.
Plantings with weed mat mulch must have drip irrigation located under the weed mat and these
are often fertigated (see nutrient presentation).
44
Trellising
Trellising is now recommended in the PNW for fields intended for fresh market or processing.
Trellising improves hand- and machine-harvest efficiency, reduces wind damage to young
blueberry plants (e.g. ‘Liberty’ is sensitive to blowing over – see cultivar presentation), and
reduces fruit drop or loss when planting are sprayed during fruit production (e.g. for SWD
control). In an 8-year study comparing trellised and un-trellised ‘Bluecrop’, trellising reduced
losses during machine harvest by up to 8% of total yield – a trellis is thus paid for in one year
when machine harvesting (Strik and Buller, 2002). A trellis system consists of end posts (either
metal or wood), T-line posts, adjustable cross bars, and 2 galvanized, high-tensile, 12-gauge
wires. Line posts are typically spaced 20’ apart. Good wire tighteners are needed to keep a strong
tension on the wires to support the crop loaded canes. The wires should be raised as the plants
age. A trellis is generally installed in year 1 or 2.
45