Fresh Market Strawberries Research Articles

Supporting Successful Transition to the Fresh Market: Research and Extension Needs of Pacific Northwest Strawberry Growers

Pacific Northwest North America (PNW) strawberry (Fragaria ×ananassa) growers are transitioning away from the processing to fresh-market sector in response to changes in local and regional markets. However, many of the regional cultivars bred for the PNW were not developed for the fresh market. There is a need to gain a better understanding of growers’ priority traits and their relative importance to enable breeders, researchers, and extension specialists to better serve this growing industry. The objective of this study was to provide such information on strawberry genetic traits of importance for the changing strawberry industry in the PNW with an emphasis on fresh-market production. Six surveys were administered to 32 growers representing ≈53%, 23%, and 15% of the total strawberry acreage in Oregon, Washington, and British Columbia, Canada, respectively. Growers ranked the relative importance of five plant and fruit traits, including fruit quality, disease resistance/tolerance, insect pest resistance/tolerance, plant stress tolerance, and other plant factors. Information about target markets, marketing channels, and general grower characteristics were also obtained. Whereas overall responses differed among the surveyed locations, fruit quality was considered the most important trait across all locations, with disease resistance/tolerance as the second most important. Specific fruit quality traits of importance were external appearance free of defects, skin color, size, sweetness, firmness, and flavor, whereas phytonutrients, seed color, and low drip loss after freezing and thawing were less important. Plant stress tolerance was identified as less important for strawberry growers in all locations. Results also showed many growers have already or are in the process of transitioning to the fresh market. Information obtained from this survey can be leveraged to target important breeding traits for fresh-market strawberry breeders within the PNW. Results also suggest priority areas of synergistic research and outreach activities to help growers achieve high fruit quality while managing diseases for fresh-market producers.

Management of Xanthomonas fragariae with Pre- and Postharvest Treatments to Overcome Trade Barriers for California Strawberries.

Xanthomonas fragariae, the causal agent of angular leaf spot (ALS) of strawberry, is a quarantine pathogen in some export markets, causing trade restrictions and economic loss to the California fresh-market strawberry industry. Preharvest chemical management options are limited to copper, and there are no postharvest treatments available that reduce populations of the pathogen if ALS is detected at an export destination. Here, we report high preharvest efficacy for the experimental bactericide amino thiadiazole and the commercial product zinc thiadiazole, alone and in mixtures with low rates of copper or the antibiotic kasugamycin, with average disease incidence reduction of up to 92.8% compared with the control. Although effective against quarantine insect pests of strawberry, postharvest methyl bromide fumigation was ineffective against X. fragariae in diseased plant tissue at a standard commercial rate. Postharvest propylene oxide fumigation, used for decades by the California nut industries for insect and microbial disinfestation, significantly reduced X. fragariae populations in infected leaflet tissues by at least 2.5-log compared with controls at a dose of ≥142 µg/ml for 2 h at 15 to 20°C. Fumigated leaflets showed little to no phytotoxicity at effective rates, and fumigated fruit were not significantly affected in appearance or susceptibility to postharvest gray mold or Rhizopus rot following storage at 2°C for 3 days and at 15°C for an additional 5 days. Together, these new treatments offer potential strategies for establishing a systems approach with preharvest treatments significantly reducing the risk of ALS on plants and, in response to quarantine detections, a postharvest fumigation treatment that reduces viable pathogen populations in existing lesions.

The development of drosophilid species (Diptera, Drosophilidae) in different strawberry cultivars

Drosophilids were not considered to be agricultural pests as they develop in overripe and fermented fruits. With the arrival of invasive species of Drosophila suzukii (Matsamura, 1931) in Europe the status of drosophilids was changed as the species is able to develop in healthy, unwounded and ripening fruits causing economic losses in production of softskinned fruits. The first economic damages from D. suzukii in Croatia where observed in production of fresh market strawberry. The aim of this study was to determine which species of drosophilids can develop in strawberry fruits. The samples of fruits of three strawberry cultivars (‘Albion’, ‘Portola’ and ‘San Andreas’) were collected during the harvest season of 2016 at greenhouse cultivation farm near Zagreb (N 45° 41′ 24″, E 16° 24′ 0″). From each cultivar 50 samples of fully ripened fruit were randomly selected and placed into the chamber for insect development to a specific temperature and humidity regime. After development of flies, three drosophilid species: Drosophila immigrans Sturtevant, 1921 ; Drosophila simulans Sturtevant, 1919 and D. suzukii were identified. An analysis of variance showed statistically more drosophilids in cultivar ‘Albion’ compared to the other two cultivars. It was concluded that species D. immigrans and D. simulans can also develop in strawberries and damage the fruits if the fruit is primarily damaged by D. suzukii and also that drosophilids prefer the cultivar ‘Albion’ for development.

Variability of free and glycosylated volatiles from strawberries destined for the fresh market and for processing, assessed using direct enzymatic hydrolysis

Free- and glycosylated-volatile profiles of 14 strawberry varieties, 9 for industrial processing (‘Darselect’, ‘Clery’, ‘Honey’, ‘Honeoye’, ‘Siabel’, ‘FCMO060’, ‘Fraise19’, 2 ‘Senga Sangana’) and 5 for fresh market (‘Gariguette’, ‘Charlotte’, ‘CIR121’, 2 ‘Clery’ (full-field and hydroponic)), were compared. All volatiles were analysed by GC-MS. Volatiles from glycosides were first released by direct enzymatic hydrolysis. The extraction method was optimised for furaneol, a key component of strawberry aroma. More than 60 volatile compounds were identified, the most abundant being butyl acetate (average: 17 mg/kg), furaneol (average: 2 mg/kg) and free hexanoic acid (average: 3 mg/kg). Free-volatile profiles showed a split between fresh market strawberries, distinguished by esters and carbonyl molecules like isobutyl acetate or hexanal, and strawberries for processing, distinguished by molecule like 3-penten-2-one and 1-butanol. The three ‘Clery’ profiles were different notably in their hexanal, 4-vinylguaiacol and 3-penten-2-one concentrations. The glycosylated volatile profiles were similar among most strawberry varieties with, as major glycosylated volatiles, hexanoic acid (average: 1.7 mg/kg), benzyl alcohol (average: 0.5 mg/kg), gamma-decalactone (average: 0.5 mg/kg) and coumaran (average: 2.5 mg/kg). The potential for volatile enhancement by deconjugation was different. Potentially fresh market strawberries had a volatile increase of 6% against 50% for strawberries for processing.

What Consumers Are Looking for in Strawberries: Implications from Market Segmentation Analysis

ABSTRACTAn online choice experiment was conducted to investigate U.S. consumer preferences for attributes of fresh market strawberry fruit. Using a latent class logit model, three different groups of consumers are identified: “Balanced Consumers,” “Experience Attribute Sensitive Consumers,” and “Search Attribute Sensitive Consumers.” This information on consumer segmentation can help the fresh market strawberry industry identify target markets, and provides valuable information to breeders, growers, and retailers to prioritize fruit attributes in their breeding, growing, or product sourcing decisions.

Survival of Salmonella spp. on surface-inoculated forced-air cooled and hydrocooled intact strawberries, and in strawberry puree

Fresh-market strawberries are cooled to 1–3 °C before commercial storage and distribution; typically by forced-air cooling. Hydrocooling ensures a faster and more uniform cooling of strawberries, although its effect on reducing microbial contamination on the fruit has not been evaluated. Salmonella has been reported to survive on damaged strawberries, but is unable to multiply, potentially due to the low pH or other intrinsic factors associated with strawberries. This study evaluated Salmonella survival a) on the surface of intact hydrocooled or forced-air cooled strawberries; b) as affected by agitation and density of packing during hydrocooling and c) as affected by pH, temperature and food matrix (strawberry or tomato puree). Intact strawberries inoculated with Salmonella were subjected to forced-air cooling or hydrocooling in water containing 100 or 200 ppm HOCl. Salmonella population was enumerated 0, 7 and 8 days post-treatment. Strawberry and tomato puree (pH 3.7 and 4.6) spiked with Salmonella and incubated at 4, 10 or 25 °C, were evaluated at 0, 1 and 3 days post-inoculation (n = 9). Compared to forced-air cooling, hydrocooling significantly reduced Salmonella survival on inoculated intact strawberries, with levels below the enumerable limit (1.5 log CFU/berry) by day 8. Hydrocooling reduced the initial Salmonella levels by 1.9 log CFU/berry, while the addition of 100 or 200 ppm HOCl reduced levels by 3.5 and 4.4 log CFU/berry, respectively. Initial Salmonella populations (day 0) were significantly lower when the berries were agitated or loosely packed during hydrocooling. Salmonella survival was significantly higher at a higher pH (4.7) compared to lower intrinsic pH (3.6) of strawberry puree. Higher temperature (25 °C) was conducive for Salmonella survival on strawberry puree compared to lower temperatures (4 and 10 °C). The data shows that a lower pH of 3.6 or refrigeration below 10 °C are effective in controlling the survival of Salmonella on damaged strawberries.

Reusing Plastic Mulch for a Second Strawberry Crop: Effects on Arthropod Pests, Weeds, Diseases and Strawberry Yields

Florida is the second largest producer of fresh-market strawberries (Fragaria × ananassa Duchesne; Rosales: Rosaceae) in the United States. The annual hill “plasticulture” production system used to grow strawberries makes this crop one of the most expensive to produce. The cost of production may be reduced if synthetic mulch can be reused and the dead plants (thatch) from the previous season left in the field, without negatively affecting crop yields. Field studies were conducted during the 2010/2011 and 2011/2012 strawberry growing seasons to evaluate the effect of re-using plastic mulch with or without dead strawberry plants from the previous season on arthropod populations, disease incidence, weeds and strawberry growth, and marketable yields of strawberries. The study was conducted in a commercial field in Citrus County, Florida using 2-yr old synthetic mulch on the bed. Two strawberry varieties ‘Albion’ and ‘Florida Festival’ were planted in 2010/2011 and 2011/2012 growing seasons, respectively. During transplanting, one treatment had all strawberry thatch (dead plant debris from previous season) removed from the soil before planting the new strawberry transplants, while in the second treatment the thatch was left to grow with the transplants. Data were collected throughout the growing seasons on plant growth, spider mites and insect pest populations, weeds, disease incidence, and marketable yield of strawberries. Re-using plastic mulch with or without strawberry thatch had no significant effect on plant size or populations of beneficial and pestiferous arthropods. However, re-using mulch with strawberry thatch reduced weed growth but increased the incidence of fungal diseases. As a result of fungal diseases and plant mortality, marketable yield for the variety “Florida Festival”, but not “Albion” was significantly lower in plots with the strawberry thatch than in those without thatch.

Development and Impact of the Spotted Wing Drosophila, Drosophila suzukii, in Florida Strawberries

Drosophila suzukii (Diptera: Drosophilidae), an Asian pest of strawberries and other thin-skinned fruit, was first detected in the Americas in California in the fall of 2008, and its first discovery in Florida came on 4 August 2009 in Hillsborough Co. Although D. suzukii is now found throughout much of Florida, no commercially damaging larval infestations have been reported in fresh market strawberries. Although other drosophilids were present in surveys, only Drosophila melanogaster appears to be a formidable competitor for D. suzukii in strawberries and may prevent or even conceal economic damage in strawberries held for processing.

CURRENT SITUATION OF THE SPANISH PUBLIC STRAWBERRY BREEDING PROGRAM

Due to the economic and social significance of strawberry production for fresh-market in Huelva (Southwest coast of Spain), an increasing research effort is undertaken in strawberry breeding in Spain in order to give response to the producers and consumers demands. In this sense, in 2006 a new stage of the Spanish public strawberry breeding program started aiming to develop and release fresh market strawberry cultivars well-adapted to the agronomic and environmental conditions of Huelva. The new cultivars to be obtained must have a harvest calendar appropriate for the economic interest of the farmers, high yielding capacity, and high fruit quality. The resulting cultivars should also be competitive with cultivars released by other origins. Parameters related with the antioxidant capacity and adaptation to different culture techniques (soil-less culture, early planting, ...) have recently been incorporated in this program. The procedures and the new most promising selections of this program are described. In the current strawberry breeding program (CC05-024-C3-1) participate, along with the Instituto de Investigacion y Formacion Agraria y Pesquera (IFAPA), the Instituto Nacional de Investigacion y Tecnologia Agraria y Alimentaria (INIA), the Instituto Valenciano de Investigaciones Agrarias (IVIA) and the private companies Fresas Nuevos Materiales S.A. (FNM), Nuevas Tecnicas en Fresa S.L. (NTF) and Freshuelva Viveristas (FV).

Hydrocooling as an Alternative to Forced-air Cooling for Maintaining Fresh-market Strawberry Quality

Hydrocooling was evaluated as an alternative to forced-air cooling for strawberry (Fragaria × ananassa) fruit. `Sweet Charlie' strawberries were cooled by forced-air and hydrocooling to 4 °C and held in different storage regimes in three different trials. Quality attributes, including surface color, firmness, weight loss, soluble solids, and ascorbic acid content, pH and total titratable acidity, were evaluated at the full ripe stage. Fruit hydrocooled to 4 °C and stored at different temperatures for 8 or 15 days showed overall better quality than forced-air cooled fruit, with significant differences in epidermal color, weight loss, and incidence and severity of decay. Fruit stored wrapped in polyvinylchloride (PVC) film after forced-air cooling or hydrocooling retained better color, lost less weight, and retained greater firmness than fruit stored uncovered, but usually had increased decay. There is potential for using hydrocooling as a cooling method for strawberries.

Simulated In-Transit Vibration Damage to Packaged Fresh Market Grapes and Strawberries

Packaged fresh market strawberries and grapes were subjected to vibration conditions which simulate truck transportation. Frequencies ranged from 2 to 30 Hz. Fruit quality was evaluated by several methods before vibration, after vibration, and after a one-week storage period. Effects of vibration frequency and box position in a 9 or a 15 high stack on fruit damage were investigated. The frequency range of 5.0 to 10 Hz caused the maximum damage to both commodities and the top box in this range was the worst for the strawberries.

Annapolis and Cornwallis strawberries

Annapolis and Cornwallis are short-day, fresh market strawberry (Fragaria × ananassa Duch.) cultivars with resistance to red stele root rot caused by Phytophthora fragariae Hickman. Annapolis, which produces large fruit, is early ripening. Cornwallis, which ripens in the early to mid-season, may have some processing applications. Key words: Fragaria × ananassa, fruit breeding, Phytophthora fragariae

Development and Estimation of Aphid Populations Infesting Annual Winter Plantings of Strawberries in California

Temporal occurrence and sampling of aphids infesting fresh market strawberries were investigated in two successive annual winter plantings in Orange County, Calif. Chaetosiphon fragaefolii (Cockerell) was the dominant species as well as the primary cause of contamination. Aphis gossypii Glover was also a contaminant, but did not reach population densities as high as C. fragaefolii. Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) were less common and were of minor importance. Aphid densities in excess of a log (x + 1) value of 1.5 (30.6 aphids) per plant resulted in contaminated fruit. Populations of C. fragaefolii on the youngest or oldest leaves co-varied with total populations, but this technique was not reliable for the other species. A binomial sampling plan based on the presence or absence of aphid infestations on the oldest trifoliate leaf per plant provided an efficient and conservative estimate for determining when pesticide applications are necessary.