.2 billion, accounting for 79% of the total U.S. gross sales ( National Agricultural Statistics Service, 2007 ). California nurseries produce more than a billion strawberry runner plants annually with a total value of ≈$60 million ( California Strawberry
Steven A. Fennimore, Milton J. Haar, Rachael E. Goodhue and Christopher Q. Winterbottom
Zahangir Kabir, Steven A. Fennimore, John M. Duniway, Frank N. Martin, Gregory T. Browne, Christopher Q. Winterbottom, Husein A. Ajwa, Becky B. Westerdahl, Rachael E. Goodhue and Milton J. Haar
For years, strawberry (Fragaria ×ananassa L.) runner plant nurseries have relied on methyl bromide (MB) fumigation of soil to produce healthy transplants. Methyl bromide, however, has been phased out due to its environmental risks. The potential for alternative fumigants to replace MB was evaluated at low and high elevation strawberry nurseries in California. The alternative fumigant iodomethane plus chloropicrin (IMPic) and a nonfumigated control (NF) were compared to methyl bromide plus chloropicrin (MBPic) at a low elevation nursery (LEN) and at a high elevation nursery (HEN) near Susanville, Calif. At a HEN near Macdoel, Calif., MBPic was compared to alternative fumigants IMPic, 1,3-dichloropropene plus chloropicrin mixture (Telone C35) followed by dazomet, chloropicrin (Pic) followed by dazomet and NF. Plants produced at the LEN were transplanted at the Macdoel HEN to measure the effects of soil fumigant history on plant health and runner plant production. Plants produced at both high elevation nurseries were evaluated for fruit yield and quality at two commercial fruit production sites in soils previously fumigated with MBPic or Pic. Runner plant production at the nurseries was similar in plots fumigated with either MBPic or alternative fumigants. All fumigation treatments had higher runner plant production than plants produced for two production cycles on NF soils. Generally, fruit yields from nursery plants produced on soils fumigated with IMPic, Pic followed by dazomet, or Telone C35 followed by dazomet, were similar to fruit yields from plants produced on MBPic fumigated soils. Overall, our results indicate that preplant soil treatments with IMPic, Pic followed by dazomet, and Telone C35 followed by dazomet, are potential alternatives to MBPic fumigation for strawberry runner plant nurseries. Fruit yields by plants in MBPic and Pic fumigated soils were comparable; however, they were more variable in Pic fumigated soils. Chemical names used: 1,3-dichloropropene (1,3-D), methyl bromide, methyl iodide (iodomethane), trichloronitromethane (chloropicrin), tetrahydro-3, 5-dimethyl-2 H-1,3,5-thiadiazine-2-thione (dazomet).
Kirk D. Larson
Each year, 500,000,000 bare-root plants (crowns) are used to establish strawberry plantings in California. Careful placement of plants in the planting holes is a critical determinant of plant growth and productivity, but large-rooted crowns are difficult to plant correctly. Use of uniform plant material would facilitate proper planting. I conducted a study in 1997–98 to determine the influence of three root pruning treatments on performance of `Camarosa' bare-root strawberry plants. Crowns were machine-dug from a nursery on 27 Oct. 1997. Two-hundred-forty plants were selected for uniformity of size, and root systems of all selected plants were >12.7 cm in length. Root systems of individual plants were randomly subjected to three pruning treatments: nonpruned (NP), pruned to 8.9 cm in length (P1), or pruned to 4.45 cm in length (P2). Twenty plants were randomly selected from each pruning treatment, washed, divided into excised and intact root tissues, and dried at 70 °C for 6 days. Pruning resulted in the removal of 23% and 78% of root dry mass for plants in the P1 and P2 treatments, respectively. For each treatment, the 60 remaining plants were established in raised beds at the Univ. of California South Coast R.E.C. in Irvine on 1 Nov. 1997. Experimental design was a RCB, with one 20-plant plot per treatment in each of three replicate blocks. There was no plant mortality and no difference among treatments in plant canopy diameter in March (mean diam. = 36.7 cm). Fruit yields were determined for each plot at weekly intervals from 1 Feb. to 18 Apr. 1998. There was no effect of pruning on yield or fruit size, suggesting that strawberry root systems have considerable regenerative ability.
Daniel S. Kirschbaum, Kirk D. Larson, Steven A. Weinbaum and Theodore M. DeJong
The pattern of total nonstructural carbohydrate [starch and soluble sugars (TNC)] accumulation in strawberry (Fragaria ×ananassa Duch.) nursery runner plants, cv. Camarosa, was determined for three growing seasons. A similar study was conducted on `Selva', but for only one year. Growth, development and fruit production patterns of plants transplanted to growth chambers (GC) or fruiting fields were also evaluated. The experiments were carried out on plants propagated in high latitude (41°50' N) nurseries in California (Siskiyou County). Plants were sampled beginning late summer through early autumn and analyzed for dry mass (DM) and TNC. Plants from different digging dates were established in GC or fruit evaluation plots in Irvine, Calif. (33°39'N). Initial TNC concentration in storage tissues at the time of nursery digging increased steadily from the second week of September to the third week of October. Crown and root TNC concentration and content were correlated positively with the accumulation of chilling units (CU = hours ≤7.2 °C) in the nursery. Root TNC concentration consistently increased from 6% to 10% DM in `Camarosa' (a short-day cultivar), and from ∼4% to 14% DM in `Selva' (a day-neutral cultivar) from mid-September to the first week of October. The root TNC content increased ∼2.5 times in `Camarosa' and ∼3.7 times in `Selva' during the same period. Transplant growth, development, and fruiting pattern were affected by digging date. Root TNC concentration and content were more sensitive to CU accumulation than crown TNC concentration and content. Therefore, root sampling appeared to be more appropriate than crown sampling for assessing the carbohydrate status and optimal digging dates of strawberry nursery runner plants early in the fall.
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.
Douglas V. Shaw, Thomas R. Gordon and Kirk D. Larson
Strawberry runner plants from the cultivar `Selva' (Fragaria ×ananassa Duch.) were produced using three nursery treatments in each of three years: propagation in soil fumigated with a mixture of 2 methyl bromide: 1 chloropicrin (w/w) at 392 kg·ha-1, propagation in fumigated soil but using planting stock inoculated prior to nursery establishment with a conidial suspension of Verticillium dahliae (106 conidia/mL), and propagation in nonfumigated soil naturally infested with V. dahliae. Runner plants were harvested and stored at 1 °C for 6, 18, or 34 days prior to establishment in fruit production trials. No significant differences were found between runner plants grown in naturally infested soil and runner plants obtained from artificially inoculated mother plants for V. dahliae infection rates detected by petiole isolation immediately prior to transplanting, the percentage of plants visibly stunted due to disease during the following production season, and seasonal yield compared with corresponding noninfected controls. Cold storage of runner plants for 18 or 34 days, produced using either natural or artificial inoculation systems, reduced the initial percentage of infected plants by 42% to 61% and the percentage of stunted plants during the following fruit production season by 43% to 57%, compared with plants from corresponding nursery treatments given only 6 days post-nursery cold storage. Yields for inoculated plants with 6 days cold storage were 16% to 20% less than those for uninoculated controls, whereas yields for inoculated plants with 18 or 34 days of storage were 3% to 9% less than the respective controls. Most of the cold storage effects on initial infection rate, stunting, and yield were realized at the 18 days of storage treatment. A reduction in the fraction of V. dahliae infected plants due to cold storage, suggests either a direct effect of cold storage on the disease organism or stimulation of secondary resistance mechanisms in the plant. Chemical name used: trichloronitromethane (chloropicrin).
Kirk D. Larson and Douglas V. Shaw
Bare-rooted `Camarosa' strawberry runner plants were established in a fruit production field on 1 Nov. 1993 using annual hill culture and two preplant soil fumigation treatments: 1) a mixture of 2 methyl bromide: 1 chloropicrin (wt: wt, 392 kg·ha-1) injected into the soil before forming raised planting beds (MBC); or 2) nonfumigation (NF). At about 33-day intervals between mid-January and the end of May, 20 plants were destructively sampled from each treatment to determine leaf dry mass (LDM), crown dry mass (CDM), root dry mass (RDM), and shoot: root dry mass (SRDM) ratios. Plant mortality was <0.2% throughout the study and did not differ with soil treatment. Regardless of sampling date, LDM, CDM, and RDM were greater for MBC plants than for NF plants, although treatment differences were not always significant. During the first 143 days, NF plants allocated a greater proportion of dry matter to roots than to shoots compared to MBC plants, indicating that roots are a stronger sink for photoassimilate in nonfumigated than in fumigated soils. However, there was no difference between treatments in SRDM by the end of the study. Fruit yield and a 10-fruit weight were determined at weekly intervals from mid-January until 23 May 1994. Yield and mean fruit weight of NF plants were 72% and 90%, respectively, of that of MBC plants. For both treatments, about one-half of total fruit production occurred between 144 and 174 days after planting (late March to late April). During that same period, rates of dry matter accumulation in leaf, crown, and root tissues decreased for plants in both treatments, but greatest reductions occurred in NF plants. Chemical name used: trichloronitromethane (chloropicrin).
Eva García-Méndez, David García-Sinovas, Maximo Becerril, Antońeta De Cal, Paloma Melgarejo, Anselmo Martínez-Treceño, Steven A. Fennimore, Carmen Soria, Juan J. Medina and Jóse M. López-Aranda
Spain is for preplant fumigation in strawberry ( López-Aranda et al., 2002a ). In 2005 and 2006, 230 t of MB was applied to 1300 ha in Castilla-Leon strawberry nurseries. More than 600 million strawberry runner plants per year were harvested and shipped
James P. Gilreath and Bielinski M. Santos
methyl bromide for strawberry runner plant production HortScience 40 1709 1715 Morales-Payan, J.P. Santos, B.M. Stall, W.M. Bewick, T.A. 1999 Influence of nitrogen fertilization on the competitive interactions of cilantro ( Coriandrum sativum ) and purple
Takashi Ikeda, Keisuke Yamazaki, Hiroshi Kumakura and Hiroshi Hamamoto
(uncooled) medium (○) in the ( A ) 2003 and ( B ) 2005 experiments. Strawberry runner plants were transplanted on 4 Sept. 2003 and 2 Sept. 2005 into the culture system. Each symbol is the mean of temperatures taken on the hour from 7 am to 6 pm each day