Recent Accomplishments

Berry Research: Recent Findings

Principal Investigator: Dr. Bernadine Strik.
Research Assistant: Gil Buller
Research Technician, cooperative breeding program: Connie Pace

Blueberries

Nitrogen uptake and distribution: A graduate student (Pilar Banados) is evaluating the uptake of N15 and (depleted ammonium sulfate -- rate and time of application) on yield, fruit size, and N partitioning in new and mature plantings of ‘Bluecrop’. We are also evaluating the effect of a late N application on growth/yield and how N is stored in the plant. [with T. Righetti]
Early cropping: In ‘Bluecrop’ we found that plants cropped in 1994 and 1995 had a significantly higher yield/plant than those in which blossoms were removed with early-cropped plants producing 14% and 21% greater yield at the 1.5' and 4' spacing, respectively. This “surprise” led us to establish a new planting in 1999 to look at the effect of early cropping (no blossom removal the first two years) on subsequent yield of ‘Duke’, ‘Elliott’, and ‘Bluecrop’ at 1.5' and 4' spacing. Early cropping (year one and two after planting) reduced the dry weight of all plant parts in February, 2002 in all cultivars. In year 3 (blossom removed treatments cropped for the first time), total yield per plot, picking efficiency and berry weight were significantly affected by cultivar, in-row spacing, and early cropping. Early cropping reduced yield in year three (2002) by 18% in ‘Bluecrop’, 26% in ‘Duke’, and 54% in ‘Elliott’. Yield was much higher at 1.5’ in-row spacing than at 4’ spacing. This study is still in progress.
We are also evaluating the effect of cultivar and in-row spacing on populations of mycorrhizae [with W. Yang and C. Scagel]
In-row spacing and trellising on machine-harvested yield of Bluecrop: This eight-year study has just been completed. Cumulative yield (1996-01) was 106% higher at the 1.5' spacing (41 tons/a) and 46% greater (29 tons/a) at the 3’ spacing than the 4' spacing (20 tons/a). In-row spacing had no effect on percent of total yield lost on the ground during machine harvest. Losses to machine harvest in un-trellised plots averaged 12 to 24% of total yield. Trellising improved machine harvest efficiency by as much as 7.8% of total yield. Pruning has taken as much as 98% longer at the high density.
Pruning of blueberries: We studied pruning method/severity in mature ‘Bluecrop’ and ‘Berkeley’: 1) “conventional” pruning with removal of unproductive canes, thinning of one-year-old shoots at the base of the bush, and removal of any unproductive wood or thinning of excessive fruiting wood near the top of the bush, as required; 2) “speed” pruning involving removal of one or two of the most unproductive canes at the base of the bush; and 3) “un-pruned” where no pruning was done for 5 years. Un-pruned plants had greater yield than conventionally pruned plants while speed pruning resulted in intermediate yields. Un-pruned and speed-pruned plants produced berries that were 19 to 27% smaller than conventionally pruned plants. The harvest season of un-pruned plants began 3 to 5 days later and lasted a week longer than that of conventionally pruned plants. The harvest efficiency of un-pruned plants was reduced as much as 51% in the later years of this study and was most closely correlated with berry weight. Conventionally pruned plants had a significantly higher percentage of the above-ground dry weight allocated to one-year-old wood and crown than un-pruned plants. Strik, B., G. Buller, and E. Hellman. 2002. Pruning Severity Affects Yield, Berry Weight, and Hand Harvest Efficiency of Highbush Blueberry, HortScience (in press).

Aronia
Cultivar evaluation: Evaluated Aronia melanocarpa ( ‘Albigowa’, ‘Darbrowice’, ‘Egerta’, ‘Kutno’, ‘Nero’, and ‘Nowa Wies’) planted in 1997. Yield in 1999 ranged from 4.4 to 12.4 kg/plant with 'Nero' having highest yield. Plants were pruned for the first time in winter 2000/01. In 2001, 'Nero' produced the highest yield (24.1 kg/plant ) and 'Egerta' the lowest (13.1 kg/plant ). Berries were 2.0 to 2.8 g. Strik, Finn, and Wrolstad. 200_. Performance of Chokeberry (Aronia melanocarpa) in Oregon, USA. Acta Hort. (in press).

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Blackberries

Alternative production systems in Marion: We are looking at various combinations of in-row spacing and primocane management to improve yield, cold hardiness, reduce thorn contamination, and potentially facilitate machine training in the “off year”.
Minimizing thorn contamination in machine-harvested Marion: Work is on-going to try to minimize risk of thorn contamination in machine harvested ‘Marion’ blackberry fruit by using a standard machine harvester in February to remove debris or a machine equipped with brushes. A machine harvester followed by brushing in February reduced thorny petioles/plot by 66% compared to an untreated control without adverse effect on yield. Strik and Buller, 200_. Reducing Thorn Contamination in Machine Harvested ‘Marion’ Blackberry. Acta Hort. (in press)
No prune system in Marion: Training primocanes of ‘Marion’ over dead floricanes (without removing/cutting off dead canes) may improve yield -- however, results have been inconsistent. This training system should not be machine harvested as it increases thorn content in harvested fruit. Training primocanes over dead floricanes has increased incidence of cane disease.[with J. Fisher and W. MaHaffee].
Raspberry Bushy Dwarf Virus: (RBDV) was discovered in ‘Marion’ blackberry at the NWREC. RBDV had no effect on cane growth or fruit number, but reduced yield (40 to 50%), fruit weight (23 to 40%), and drupelet number per fruit (36 to 39%) compared to uninfected plants. In 2000, we surveyed 32 commercial fields to test for the presence of RBDV using ELISA. Three grower fields tested positive for RBDV. Martin, R.R. and B. Strik. 2002. Impact of Raspberry Bushy Dwarf Virus on ‘Marion’ Blackberry. Plant Disease (in press). We are also evaluating the incidence of RBDV in other blackberry genotypes [with R. Martin and C. Finn].
Nitrogen management in Kotata blackberry: Mohadjer, P., B.C. Strik, B.J. Zebarth, and T.L. Righetti. 2001. Nitrogen uptake, partitioning and remobilization in `Kotata' blackberries in alternate year production. J. Hort. Sci. and Biotech. 76:700-708.

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Raspberries:

Nitrogen uptake and distribution: A graduate student (Hannah Rempel) is evaluating the uptake of N15 (ammonium sulfate -- rate and time of application) on yield, fruit size, and N partitioning in red raspberry, ‘Meeker’. [with T. Righetti]

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Strawberries

Pre-plant options in strawberry: We are looking at various pre-plant options for strawberry: fallow; meadowfoam grown until bloom and incorporated; meadowfoam grown until seed set and incorporated; and peas grown for an early crop. We are looking at impact on plant growth, yield and various pests. No yield or pest effects were found in the first fruiting season of ‘Totem’. Work in progress [with D. Hemphill]
Nitrogen management in ‘Totem’: We just finished studying the uptake, remobilization and storage of nitrogen using N15. Treatments included foliar applications of urea-N15 at various stages of development of ‘Totem’ and granular fertilizer (Ammonium nitrate-N15) applied in spring or at renovation. Treatments were imposed in 1999. We also repeated some labeled treatments in 2000 to compare uptake to an unfertilized control. [with T. Righetti]
Deblossoming ‘Totem’ in the planting year had no significant effect on yield, berry weight, or plant yield and vegetative components in the first and second fruiting seasons. Late planting of ‘Totem’ (on flat ground) decreased yield in the first fruiting season, but not the second fruiting season. Berry weight was greater with later planting dates in both fruiting seasons. Production system had no effect on yield.
Annual production systems: Late planting in annual systems increased populations of the two?spotted mite (Tetranychus urticae) the following spring. Populations then dropped due to suppression by the predatory mite, Neoseiulus fallacis. Late planting of ‘Totem’ on raised beds did not reduce yield the following season. Second year perennial plots of ‘Totem’ had a higher yield than all annual treatments except those plots fumigated and planted in August of 1997. Data comparing annual plots to a third year perennial were collected in 1999; an economic analysis is planned [with R. Rosetta].

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Kiwifruit

Fruit thinning: The effect of three severities of fruit thinning at pre- or post-bloom on yield and fruit size of ‘Ananasnaya’ were compared in a commercial vineyard. Pescie, M. and B. Strik. 200_. Effect of time and severity of thinning on fruit quality and yield of hardy kiwifruit (Actinidia arguta). NZ J. Crop and Hort. Sci. (submitted)
Effects of shading: The effect of time of shading (50%) on current season yield/quality and flower number, fruit number, seed number, yield and fruit size the following season in ‘Ananasnaya’ was studied in a commercial vineyard. Tiyayon, C. and B. Strik. 200_. Effect of overhead shading on yield and fruit quality of hardy kiwifruit (Actinidia arguta). NZ J. Crop and Hort. Sci. (submitted)
Morphology of hardy kiwifruit: Described the growth and fruiting pattern of hardy kiwifruit. Tiyayon, C. and B. Strik. 2002. Effect of fruiting cane origin on fruitfulness of hardy kiwifruit (Actinidia arguta). NZ J. Crop and Hort. Sci., (accepted)

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Berry and Grape Extension: Recent Accomplishments

Check out the Northwest Berry and Grape Information Net -- the production and marketing guide for berries and grapes in the Pacific Northwest. Contains links to recent extension newsletters for blueberries, blackberries, raspberries, strawberries, and grapes. All NWREC berry extension agents contribute.

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Integrated Pest Management Extension

Copies of recent berry crop IPM Newsletters can be found in The IPM Corner. Visit the IPM Extension web page.

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Nursery Crops Research: Recent Findings

Principal Investigator: Dr. Sven E. Svenson.
Assistants: Thirza Collins, Kathy Sanford, Geoff Lewis

Container Design and Irrigation Frequency

Three replicate blocks were installed for high-, medium-, and low-frequency irrigation, providing the equivalent of 1-inch, 0.35-inch or 0.22-inch of rainfall, respectively. For three ornamental plants potted in 1-gal pots, three container designs were tested: traditional drainholes located at the base of the sidewall (0% water storage), drainholes raised on the sidewall to provide 20% water storage (based on a water-filled pot), or drainholes raised on the sidewall to provide 40% water storage. The experiment was a 3 irrigation frequency X 3 container design factorial treatment arrangement within a randomized complete block design using 10 representative plants of each species within each of three replicate blocks. The largest 'Hetzii' holly, 'Hino Crimson' azalea and 'Claridge Druce' geraniums were grown using high-frequency irrigation with 0% water storage or using medium-frequency irrigation with 20% water storage. Geranium shoot weight was significantly less only when grown using low-frequency irrigation in containers with 0% water storage, or when grown using high-frequency irrigation in containers with 40% water storage. Of the three species tested, only 'Hetzii' holly grew roots below the level of the raised drainholes, with these roots exhibiting thickened, enlarged diameters. No increased incidence of root disease was observed during the study. Potential advantages and disadvantages of production using containers with raised-drainholes are discussed.

Retractable Roof Systems Improve Cold Protection of Nursery Crops

When retractable roof structures operated with "cold trapping" were used for unheated cold protection of container grown nursery crops, plants required fewer irrigation applications and fewer pesticide applications. Rhododendron flowering was delayed about 4 weeks in the retractable roof structure, providing an opportunity to ship blooming plants at a later date. Based on delayed initiation of vegetative growth, crops grown in the retractable roof structure maintained cold hardiness for a longer period of time. Crops grown in the seasonally-covered Quonset structure were susceptible to frost damage before Nov. 1, and after Feb. 16 and suffered some damage, while crops grown in the retractable roof structure were always protected from extreme temperatures and had no frost damage.

Retractable Roof Systems Reduce Soil Temperatures in Containers

Ornamental crops were established under 0, 30, 47 or 63% stationary black-polypropylene shading, under 50% white-poly retractable shading, or under 30% black-polypropylene shading placed below the 50% white-poly retractable shading. Plants arranged under each shading system in a completely randomized design with a minimum of three replicate shading blocks for each shading treatment, and a minimum of five plants within each block. Substrate temperatures were recorded in 1-gal containers planted with Picea 'Conica'. The southwest (SW) region of individual containers was the hottest in mid-afternoon. Substrate temperatures were lowest under retractable shading. Observation of the SW region of the root ball revealed no root death under retractable shading. Of the 12 taxa studied, three showed increased shoot dry weights when grown under retractable shading. The cooler substrate temperatures, and maintenance of a healthy root system under retractable shading may help explain the increased growth, reduced plant "losses," and reduced incidence of root rot diseases of some plants when produced under retractable shading facilities.

Liverwort Control Studies

A series of experiments were performed to study how irrigation practices interact with other cultural procedures to influence liverwort development. Liverwort infestation increased as irrigation and N fertilization increased. The combination of hazelnut shell mulch and the herbicide oxadiazon provided good suppression of liverworts for up to 12 weeks using low frequency irrigation application. In general, reducing irrigation frequency enhances the liverwort suppression of mulches, herbicides and fertilizers. The data supports speculation that the recent increase in liverwort infestations in Oregon nurseries is related to the increased rainfall in the region over the past few years. High frequency irrigation increased liverwort coverage of the surface of the growing substrate.

Increasing the amount N from a 20N-9P-17K fertilizer increased liverwort coverage, with nitrogen levels from 100 to 200 mg/liter (ppm) supporting the most coverage.

Hazelnut shells, oyster shells and copper-treated geotextile disc provided good suppression of liverwort growth for up to 6 weeks. Coarse sand, perlite, pumice and untreated geotextile discs suppressed liverwort growth under low frequency irrigation, but not under high frequency irrigation. Liverworts grew on the substrate surface below the untreated geotextile discs.

Surface-applied microelement fertilizers and surface applied preemergent herbicides suppressed liverwort growth with low-frequency irrigation. However, high frequency irrigation eliminated or reduced the effectiveness of these treatments. The combination of hazelnut shells and oxadiazon provided good suppression of liverwort growth for up to 12 weeks with low frequency irrigation, and the combinations of hazelnut shells or pumice with oxadiazon provided suppression for 8 weeks with high frequency irrigation. Liverwort growth appears to be optimized by high frequency irrigation and nitrogen rates between 100 and 200 mg/liter (ppm). irrigation frequency enhances the suppression of liverworts by mulches, surface-applied fertilizers or preemergent herbicides, whereas high frequency irrigation allows liverwort to avoid suppression. The best treatment for liverwort suppression in this study was a combination of low frequency irrigation, a hazelnut shell mulch, and the application of oxadiazon at label rates.

Root Weevil Controls (with Robin Rosetta as Co-PI)

For Thuja, no treatment influenced adult root weevil mortality until three days after application. Cryolite had the highest percentages of dead or moribund adult weevils three days after application. Eight days after application, Pinpoint and Cryolite had killed more weevils compared to Topcide or the untreated controls.

For Rhododendron one day after application, the percentage of dead adult weevils was higher for Cryolite and Gowan 1885 compared to all other treatments. Seven days after application, Cryolite, Gowan 1885 and the Pinpoint treatments had higher percentages of dead weevils compared to the Topcide treatments or the untreated controls.

Soil-applied insecticides provide a useful alternative to foliar cover sprays for adult root weevil control. Cryolite, Gowan 1885, and Pinpoint 15G (high rate) had the highest mortality (70% to 79%) compared to untreated or Topcide-treated plants. Pinpoint 15G and both sodium aluminofluoride bait treatments may provide an effective, viable option for adult root weevil control when pesticides cannot be applied in the evening, or when foliar cover sprays may harm nontarget organisms.

Controlling Weeds and Rooting-Out in Sandbed Subirrigation Systems (with Dr. Robert L. Ticknor, emeritus, and Dr. Dave Adams, emeritus, as CO-PI's)

Both Surflan and Snapshot provided good control of fireweed growth on the surface of the sandbed. Daphne shoots were shorter when grown on SnapShot-treated sandbed plots, but shoot weight was not influenced by herbicides. Both Surflan and Snapshot completely prevented rooting-out. Using a low water level in the sandbed reduced the number of fireweeds by about one third. Use of treated or untreated weed barriers significantly reduced fireweed growth at both low and high water levels, with the copper-treated barrier improving weed control in the high water level treatment. Compared to all other treatments, Forsythia shoot size was smaller when grown on copper-treated barriers in the low water level plots. Erica shoots were larger when grown on barriers in the high water level plots. While rooting-out of Erica was eliminated by placing treated or untreated weed barriers on the sandbed surface, rooting-out of Forsythia was controlled only by copper-treated barriers). Richards (1975) suggested that the water level in the sandbed could be regulated to prevent rooting-out. In this study, both Forsythia and Erica rooted-out on uncovered plots when the water level was at the surface of the sandbed, or when the water level was two inches below the sandbed. When sandbed subirrigation is an acceptable option for nursery production, weed growth and rooting-out can be reduced or eliminated using either herbicide treatments or weed barriers placed on the sandbed surface. Since herbicides may not be labelled for this type of use, weed barriers are currently the best available option. Weed barrier pretreated with copper is presently available (Texel Industries, Spartanburg, SC), but the copper treatment may not be needed to control rooting-out for all crops.

Evaluation of Hebe species and cultivars as ornamentals for the Pacific Northwest

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Nursery Crops Extension: 1994 Findings

Lygus spp. (Lygus bugs) have been identified as being responsible for RMTD (Red Maple Terminal Disorder). Control strategies have been studied (see Regan and Rosetta, 1995, The Digger 39:17-20).

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Vegetable Research: Some Recent Findings

Green bean yield was highest at 90 kg N/ha. At this rate, residual nitrate-N in the surface 30 cm of soil at the end of the growing season was 33 kg/ha, compared to 24 kg/ha for unfertilized soil.
In 1995, yield of sweet corn was highest at 265 kg applied N/ha, but yields with as little as 135 kg N/ha were not significantly lower. Yield of sweet corn did not respond to sidedressed N when the pre-sidedress soil nitrate concentration exceeded 30 ppm. Application of up to 135 kg N/ha to sweet corn did not significantly increase residual nitrate-N in the surface 30 cm of soil. At the recommended N rate of 200 kg/ha, residual nitrate was 50 kg/ha, compared to 3 kg/ha at planting. Results were similar in 1996, but the highest yield was at 180 kg N/ha.
On-farm research on the relationship of sweet corn yield to pre-sidedress soil nitrate levels indicated that very few growers will be able to skip a mid-season sidedressing of N. However, at 9 of 16 sites in 1995 and 8 of 12 sites in 1996, a 33% reduction in sidedress N application did not reduce yield significantly. In 1997, the PSNT successfully predicted the need for additional N application in 9 of 10 grower fields. Results from 1995 through 1998 resulted in a modification of the PSNT in which sweet corn yield is optimized when the total of sidedressed fertilizer N plus soil N equals 175 lb/acre.
A survey of 34 grower fields indicated that residual soil nitrate was highest with sweet corn and beans, intermediate with broccoli and cauliflower, and lowest with beets and carrots. The highest rates of N were applied to the broccoli and cauliflower.
A winter cover crop of either cereal rye, triticale, or triticale plus common vetch, reduced the amount of nitrate leached below the root zone nearly 50% compared to a winter fallow, as measured by passive capillary samplers. This effect has been consistent for eight of the last nine winters.
A winter cover crop of red clover increased yield of a subsequent sweet corn crop in 1996 when fertilizer N was reduced. The N contribution of the clover crop was about 50 lb/acre. Sweet corn yield was reduced slightly following a triticale cover crop compared to winter fallow. In 1997, broccoli yield, when averaged over rates of applied N, increased following a cover crop of relay-interplanted red clover or fall-planted triticale plus winter pea. A triticale cover crop reduced subsequent broccoli yield.
In 1998 and 1999 trials of the effects of between-row spacing and N rate on three varieties of edamame (vegetable soybean), 'Shironomai' outyielded 'White Lion' and 'Butterbeans'. Highest yields were with the high rate of N (120 kg/ha) and 0.5-meter rather than 0.75-m spacing.
Incidence of white mold (Sclerotinium) and grey mold (Botrytis) tended to increase when snapbeans were planted through a triticale cover crop residue.
The presidedress soil nitrogen test (PSNT) was modified for use as a predictive measurement of the amount of additional N fertilizer needed to ensure maximum sweet corn yield.
Several sweet corn varieties were determined to have much lower nitrogen requirements than does the industry standard 'Jubilee.'

Cooperators in this research included N.S. Mansour and John Luna, OSU Horticulture; Richard Dick and John Hart, OSU Crop and Soil Science; John Selker, OSU Bioresources Engineering; and Carol Miles, Washington State University.

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Vegetable Extension

A 1995 trial of zucchini lines for resistance to zucchini yellows mosaic and watermelon mosaic (race II) viruses demonstrated that several lines from Asgrow Seed Co. had excellent resistance to these viruses. Some lines appeared to have quality and yield suitable for fresh market or processing crops in the Willamette Valley.
In a greenhouse cage experiment, cucumber beetles (Diabrotica undecimpunctata) did not transfer the above viruses from inoculated plants to non-inoculated plants.

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