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Mary Jo Kelly, Marvin P. Pritts and Robin R. Bellinder

Weed management continues to be a major challenge for strawberry growers who plant in the traditional matted-row production system where mother plants are set in spring and daughter plants fill in the rows over the first growing season ( Hancock et

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Timothy W. Miller, Carl R. Libbey and Brian G. Maupin

Weed control in matted-row strawberry culture systems of the Pacific Northwest (PNW) is a difficult challenge. Like in most of the northern United States, PNW strawberries are usually produced in a three-year cycle with tillage used for weed and

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Joseph A. Fiola, Gojko Jelenkovic and Gene Galletta

The major objective of the NJUS Strawberry Breeding Program is the development of early ripening cultivars with excellent fruit flavor and size for production under conventional matted-row, and high density annual production systems. In the 1993 replicated Step 3 trials (1991; 1992 planted), sixteen selections had higher yield than `Earliglow' (8127, 11312 kg/Ha), ranging from 8433 kg/Ha to 13334 kg/Ha. Thirty-one had higher weighted average fruit weight (WAFW) over the season than `Earliglow' (8.8 g; 8.4 g), ranging from 9.0 g to 12.3 g.

Selection for phenotype best suited for annual stem includes: low runnering, strong vigor, earliness, and large fruit size. In 1993 harvested Step III, four selections had comparable or higher yield (range: 12,866 to 27,128 kg/Ha) than `Chandler' (12,950 kg/Ha), as well as larger primary and WAFW (range: 13.5 to 16.4 g). All selections were significantly earlier than `Chandler'. In summary, the NJUS Strawberry Breeding Program has selections for the matted-row and annual production systems which are early, with excellent fruit flavor, size, and firmness for fresh market production.

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C.A. Weber

Adequate weed control in the establishment year of matted-row strawberries (Fragaria × ananassa) is crucial for the long-term viability of plantings. Suppression of weed growth until the new strawberry plants are established and runners rooted is an effective strategy in new plantings. Three biodegradable mulch films were compared to standard weed control for establishing matted-row strawberries. Two films were test products using a biodegradable polymer, either clear or black, covering brown 40-lb kraft paper (IP40 Clear and IP40 Black, respectively). The third material was Planters paper, a black paper mulch. The films were evaluated for weed suppression, rate of degradation and effects on runner production and fruit yield. Additionally, the ability of runners that were formed to root as the film degraded was also observed. The IP40 Black mulch reduced the number of weeds compared to the standard control but did not degrade quickly enough for runners to root. The Planters paper also had fewer weeds, but it degraded quickly along the edges where it was covered by soil. This allowed the wind to tear it and blow large pieces off the plots. The IP40 Clear degraded in a timely manner and allowed runner rooting, but it was not acceptable as a weed suppression material. The IP40 Black and Planters paper mulches were effective for weed control in the establishment year, but rate of degradation was too slow in the former case and too fast in the latter. Runner production and fruit yield were not affected by any of the mulch materials compared to standard control.

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Marvin Pritts, Mary Jo Kelly and Greg English-Loeb

The strawberry bud weevil (Anthonomus signatus Say; clipper) is considered to be a serious early-season pest in perennial matted row strawberry (Fragaria ×ananassa Duchesne) plantings in North America. Adult females damage flower buds in early spring by depositing an egg in the bud, then clipping the bud from the pedicel. Action thresholds are low (two clipped buds/meter of row) because pest managers and growers have assumed that one clipped flower bud results in the loss of one average-sized fruit. Fields with a history of clipper damage are often treated with insecticides during the first period of warm weather that coincides with inflorescence development, without scouting for clipped buds or evaluating damage. We examined 12 strawberry cultivars and found that most can compensate for a significant amount of flower bud loss, provided that the loss occurs early in the development of the inflorescence. A new threshold is proposed in which the potential loss of fruit per inflorescence is considered, along with the total number of severely damaged inflorescences. We believe that in most circumstances and with most cultivars, clipper injury will remain below the damage threshold.

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Brent L. Black, Stan C. Hokanson and Kim S. Lewers

In the perennial strawberry production system, removal of the harvested crop represents a loss of nitrogen (N) that may be influenced by cultivar. Eight strawberry (Fragaria ×ananassa Duch.) cultivars and eight numbered selections grown in advanced matted row culture were compared over three seasons for removal of N in the harvested crop. Replicated plots were established in 1999, 2000, and 2001 and fruited the following year. `Allstar', `Cavendish', `Earliglow', `Honeoye', `Jewel', `Northeaster', `Ovation', and `Latestar' and selections B37, B51, B244-89, B683, B753, B781, B793, and B817 were compared for yield and fruit N concentration. Harvest removal of N (HRN) was calculated from total season yield and fruit N concentration at peak harvest. There were significant differences in HRN among genotypes, ranging from 1.80 to 2.96 g N per meter of row for numbered selections B781 and B37, respectively. Among cultivars, HRN ranged from 2.01 to 3.56 g·m–1 for `Ovation' and `Jewel', respectively. The amount of HRN was largely determined by yield, however, there were also significant genotype differences in fruit N concentration, ranging from 0.608 to 0.938 mg N per gram fresh weight for B244-89 and `Jewel', respectively. These differences indicate that N losses in the harvested crop are genotype dependent.

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David G. Himelrick and Floyd M. Woods

Generalized recommendations for the southeastern U.S. would typically include soil testing well in advance of establishment. Lime, P, and K should be applied at least 2 weeks before planting. Nitrogen is either broadcast and incorporated before planting or sidedressed 2 to 4 weeks after planting at 30 to 70 kg·ha–1. Additional N at 30 to 65 kg·ha–1 is applied late August to mid-September. A late winter N application at 20 to 30 kg·ha–1 is suggested for sandy soils. On established plantings fertilization takes place at renovation, with P and K being applied based on soil test or foliar analysis results. Nitrogen rates are typically in the range of 35 to 60 kg·ha–1. Later season fertilization generally follows the rates and timings of fall and winter recommendations of the establishment year. Minor nutrients can be limiting on sandy soils and B may be required in a wider range of soil types.

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Marvin P. Pritts and Mary Jo Kelly

Various levels of weed competition were implemented in a second-year well-established strawberry (Fragaria ×ananassa `Jewel') planting by cultivating and hand weed removal for defined periods of time over 3 years. The impact of weeds on subsequent productivity was then determined. Sixteen treatments were established where weeds were allowed to grow for defined periods (0, 1, 2, 3, 4, or 5 months) throughout the growing season. Treatments were maintained in the plots for 3 consecutive years. Spring weed biomass in 1997 had no impact on yield that same year. Weed biomass in 1997 was negatively associated with yield in 1998, although the trend was nonsignificant. However, several individual contrasts were significant. For example, the weed-free control treatment had the highest average yield, while season-long weed competition reduced yield by 14%. The inverse relationship between weed biomass and fruit yield became significant in 1999. For every 100 g·m-2 increase in weed biomass in 1998, fruit yield was reduced by 6% in 1999. Season-long uncontrolled weed growth reduced productivity by 51%. However, several plots with a limited amount of weed competition had higher yields than the continuously weeded control. These data indicate that yields from a well-established strawberry planting may not be vulnerable to a limited amount of weed competition for at least 2 years. Furthermore, data suggest that hand weeding and cultivation on a monthly basis for multiple years may be damaging as well. Growers should direct a majority of their efforts and resources toward controlling weeds in the planting year. Once the planting is well-established, growers may limit the number of times they hand weed to two or three per season.

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John Strang, Carl Harper, Dana Hadad, Kay Oakley, Darrell Slone and John Snyder

Three landscape fabrics, Magic Mat®, a heavy black plastic woven fabric with a fuzzy underside; Weed Mat®, a thin black plastic sheet with small holes; and Typar®, a dark gray spun bonded material, with and without a cover of organic oak bark mulch, were evaluated for weed control and ability of strawberry plant roots to establish through the fabrics over a 4-year period. Landscape fabrics reduced weed numbers for the first 3 years in comparison with the bare ground treatment. With few exceptions. the organic mulch did not improve the weed control capability of landscape fabrics. Fruit yield for the Weed Mat and Magic Mat treatments did not differ from the bare ground treatment, but was lower for the Typar treatment when averaged over organic mulch treatments. Fruit yield was higher where the organic mulch was used when averaged over all landscape fabric treatments. Fruit size was slightly larger for the bare ground and smallest for the Typar treatments during the first harvest season, but there was no difference in fruit size by the third year of harvest. Fruit size for the organic mulched plots was slightly larger than that for the unmulched plots the second year of harvest, but there was no difference for the first or third years. The number of strawberry runner plants that rooted and plant row vigor were greater for the Weed Mat, Magic Mat and plots without the landscape fabric than for the Typar plots, particularly in the second and third season. Rooting of runner plants and plant row vigor was better with organic mulch. Landscape fabric tended to reduce extent of rooting, especially in the first season, but it was improved by the application of organic mulch.

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Marvin P. Pritts and Mary Jo Kelly

Competition from weeds and an interplanted sudangrass [Sorghum bicolor (L.) Moensch, formerly S. sudanense (Piper) Stapf.] cover crop was allowed to occur in newly-planted strawberries (Fragaria ×ananassa Duch.) for varying lengths of time, and at different times during the growing season. Newly planted strawberries were most susceptible to weed and cover crop competition during the first 2 months after planting, as both runnering (stolon formation) and subsequent yield were impacted. In 1994-95, 1 month of weed competition in June reduced yield by 20%, whereas 2 months of weed competition reduced yield by 65%. However, 1 month of uncontrolled weed growth later in the growing season had little to no impact on yield, although weed biomass was much less then. Herbicide (napropamide) use alone was insufficient to prevent weed competition and yield reduction. In our study, yield was reduced 0.67 t·ha-1 or 5.5% for each 100 g·m-2 of weed biomass. The data suggest that it is critical for growers to minimize weed competition early in the planting year when weed growth is greatest. Since an interplanted sudangrass cover crop displaced a portion of the weeds, it could be seeded later in the year to provide some weed suppression without a negative impact on yield. Chemical names used: N, N, Diethyl-2-(1-naphthalenyloxy)-propionamide (napropamide); N-(phosphonomethyl)glycine (glyphosate).