Strawberry Production Around The World

 

Strawberry belongs to the family Rosaceae, genus Fragaria, and is among the most widely consumed fruits throughout the world. Strawberry flowers are bisexual and mostly self-pollinated.

Flowering in most cultivars is influenced by photo-period and temperature. Based on their response to photo-period, strawberry cultivars are classified into short-day cultivars eg. Sweet Charlie, Camarosa; and day-neutral cultivars  eg. Selva, Seascape. Most cultivars grow well under cool climatic conditions. However, temperatures below -0.5°C can cause severe damage to full blooms. The temperatures in European countries like Holland, Belgium, U.K. and Germany are below freezing point for a prolonged period of time during winter. Spain and Italy also have very cold winters. Growers in these countries have adopted various methods of "forced cultivation" for off-season strawberry production to take advantage of the high market prices during winter. In Holland and Belgium, strawberries are grown in glasshouses during winter using bags and pots filled with a peat-based substrate. Strawberries are also ‘forced’ under polyethylene tunnels in Spain, Italy, France, U.K. and Germany. In Israel, strawberries are cultivated under polyethylene tunnels and in greenhouses using PVC troughs and styrofoam containers filled with soilless media like a mixture of coconut coir and perlite.

 

  

 

                   Strawberries growing in troughs  (Israel)                                         Strawberries growing in styrofoam containers  (Israel)         

 

 

Strawberry Production In The United States

 

United States is the largest producer of strawberries in the world. Unlike strawberry growers in most other countries, U.S. strawberry growers are production-oriented rather than market- oriented. Although greenhouse technology for producing ‘off-season’ vegetable crops is available, strawberry growers in the U.S. have not yet adopted these techniques to increase ‘off-season’ strawberry production. Instead, they have been relying on volume sales during the regular season for making a profit. Strawberry production under protective structures like greenhouses or tunnels is not very common in the U.S. Almost 100% of the strawberry production is done in the field, using raised-beds fumigated with methyl bromide and covered with plastic mulch.

In California, strawberries are grown as a perennial crop. It is the No.1 producer accounting for 80% of the total U.S. strawberry production. However, supply of fresh strawberries from California starts decreasing by the end of October and this is where Florida strawberry growers dominate the market supply. In Florida, strawberries are grown as an annual crop and it is the second largest producer of strawberries in the U.S. Also, due to the relatively mild winters, Florida is the largest supplier of fresh strawberries during winter.

 

Growing Winter-Strawberries Under Protective Structures In Florida

 

The Florida strawberry industry survives mainly on the high market prices that prevail during the winter months of November, December and January. Florida has 6,300 acres under strawberry production. In terms of revenue earned from vegetable crops, strawberries rank third, after tomatoes and bell peppers (FASS Vegetable Summary 1999-2000). During the 1999-2000 strawberry season, 18.3 million flats were produced from November to April, with a total value of $167.58 million. However, only 11% of the total strawberry production occurred during November-December, when the average market price was high ($15.36 per flat). The bulk of the production (38% of the total) occurred in March-April, when the average market prices dropped down to $6.12 per flat (FASS Vegetable Summary 1999-2000). Any further drop in the market price makes the cost of harvesting prohibitive, and many growers have to stop picking berries after April. Thus, the key to maintain profitability in the Florida strawberry industry is to enhance winter-production during November, December and January. Growing strawberries under protective structures with new growing systems using soil-less media can enhance winter-production in Florida.

 

Hydroponic Strawberry Culture Under Plastic Greenhouses : Protected Agriculture Project

 

The Protected Agriculture Project of the Horticultural Sciences Dept., University of Florida, has been conducting various experiments to generate up-to-date, practical, and location-specific information for greenhouse vegetable production in north-central Florida. Researchers are experimenting with various growing systems and soil-less media for producing off-season strawberries under plastic greenhouses.

Presently, two experiments are being conducted in the greenhouse located at the Horticulture Unit, University of Florida, Gainesville, FL 32606.

 

The Protected Agriculture Project greenhouse located at the Horticulture Unit, Gainesville, FL 32606.

 

 

 

 

                                Left : Strawberries growing in ‘Polygal’ troughs            Right : Strawberries growing in polyethylene bags placed on the ground

 

This trial was conducted during Fall 2000 – Spring 2001, and is being repeated during Fall 2001 – Spring 2002.

Three growing systems, three soil-less media and two kinds of plug transplants of cv. Sweet Charlie were evaluated in a passive ventilated, double-poly, high-roof greenhouse located at Gainesville, FL.

 

GROWING SYSTEMS

 

The three growing systems used in this experiment are described below :

 

1) Polyethylene bag laid on the ground :

Polyethylene bags (100 x 25 x 10 cms) placed on 10 cm wide styrofoam strips covered with plastic sheet. The channel formed between the stryofoam strips acts like a gutter to drain-off the leachate.

 

2) Polyethylene bags placed on PVC gutter sections suspended in air :

 

Polyethylene bags (100 x 25 x 10 cms) are placed on 10 cm wide PVC gutter sections that are suspended 1.2 m above the ground level with 2 mm dia. steel wire.

 

 

3) Polygal troughs suspended in air :

 

This system is manufactured by Polygal Industries, Israel. The system consists of a U-shaped corrugated plastic sheet (10 cm bottom width x 12 cm wall height with 5 cm diameter holes) placed in PVC gutter sections suspended 1.2 m above ground level.

 

 

SOILLESS MEDIA

 

Three different soil-less media were used in this experiment :

1) Perlite (coarse)

2) 2 Peat : 1 Perlite mix

3) Pine bark

 

PLUG TRANSPLANTS

 

A)  4-month-old “Sweet Charlie” plugs grown in a greenhouse using a sub-fertigation system with two weeks chilling before transplanting (25°C Day / 15° Night temperature and 9 hour photoperiod). These plugs were produced at the Deptartment of Horticultural Sciences, University of Florida.

 

B)  2.5-month-old “Sweet Charlie” plugs produced at Norton Creek Farms, North Carolina.

 

EXPERIMENTAL DESIGN AND TREATMENTS

 

A total of 18 treatments with three replications are arranged in a split block design.

 

Treatments :

 

 

 

RESULTS

A total of 20 harvests were done from Nov 17 to March 10. Fruits weighing more than 10 g were considered as marketable whereas fruits that were weighing less than 10 g or deformed or diseased were considered as culls.

 

EARLY / MID-SEASON YIELD : (Nov 17 – Jan 20) :

More than 83% of the early / mid-season yield was marketable and average fruit size was 20 g in all treatments. Growing system influenced early / mid-season yield from 2.5-month-old plugs, while it had no effect on the yield from 4-month-old plugs. Plants grown in perlite produced a higher marketable fruit number and fruit weight per plant as compared to pinebark and mixture of (2 peat : 1 perlite), regardless of growing system or plug type.

 

TOTAL YIELD : (Nov 17 – March 10) :

For the total yield, there was an interaction between growing system and media, but not plug type.

Plants grown in a mixture of (2 peat : 1 perlite) produced higher yield (gm per plant) in ‘polyethylene bags placed on PVC gutter’ as compared to ‘Polygal troughs’ and ‘polyethylene bags kept on ground’.

Plants grown in pinebark produced similar (and higher) yields (gm per plant) in ‘polyethylene bags placed on PVC gutter’ and ‘Polygal troughs’ as compared to ‘polyethylene bags kept on ground’.

Plants grown in perlite produced similar (and higher) yields (gm per plant) in ‘polyethylene bags placed on PVC gutter’ and ‘polyethylene bags kept on ground’ as compared to ‘Polygal troughs’.

Plants grown in (2 peat : 1 perlite) produced greater number of fruit per plant in ‘polyethylene bags placed on PVC gutter’ as compared to ‘Polygal troughs’ and ‘polyethylene bags kept on ground’.

Plants grown in pinebark produced similar (and greater) number of fruit per plant in ‘polyethylene bags placed on PVC gutter’ and ‘Polygal troughs’ as compared to ‘polyethylene bags kept on ground’.

Plants grown in perlite produced similar (and higher) number of fruits per plant in ‘polyethylene bags placed on PVC gutter’ and ‘polyethylene bags kept on ground’ as compared to ‘Polygal troughs’.

 

 

   Strawberries growing in ‘Polygal hanging bed-pack’ troughs suspended at a height of 1.8 m above the  ground level

 

Typically, the plant density of strawberries grown in the field is 4.3 plants per m². There are limitations to increase this density in the field since wide walkways are required for operations like spraying and harvesting.

In protected strawberry cultivation, the plant density can be increased by using specially designed growing systems. The need for walkways is practically eliminated by raising the growing systems above shoulder-level and by using a fogging machine for delivering pesticides. An density trial is presently being conducted to evaluate the performance of cv. Sweet Charlie at eight different plant densities (22, 20, 18.3, 16.9, 14, 12.7, 11.7, 10.8 plants per m² ) in a passive ventilated, double-poly, high-roof greenhouse located at Gainesville, FL. The eight densities are derived by having four between-row spacings (50, 55, 60 and 65 cm center-to-center) and two within-row spacings (17.5 cm and 35 cm plant-to-plant). The growing system consists of ‘Polygal Hanging Bed-Pack’ troughs (10 cm bottom width, 12 cm wall height and 60 mm planting hole diameter) that are suspended 1.8 m above the ground level. Troughs are filled with locally available pinebark (2.5 cm² sieved). Three-month-old, greenhouse-grown plug transplants that were conditioned (25°C day / 15°C night temperature,  9 hour photo-period) for two weeks prior to transplanting are being used in this density trial. Transplanting was done on October 12, 2002. Harvesting was started in the third week of November. The early, mid-season and total yield will be recorded and the final results of this trial will be available in May, 2002.

 

Management practices like irrigation, fertilizer application, heating, pollination and biological pest control for both experiments is similar and is described below :

 

 

IRRIGATION

Plants are irrigated with a drip tape (Chapin Watermatics Inc. U.S.A.) with 5 cm emitter spacing and 9.45 ml discharge per minute per emitter. Plants receive nutrients with every irrigation and each plant receives about

140 ml nutrient solution per day. Irrigation starts at  8.00 A.M. and ends at 5.00 P.M. Every irrigation event is one minute, with 90-minute intervals between two irrigations.

 

 

FERTILIZER

Fertilizer solution is discharged by two injectors (Dosatron Inc., U.S.A.) assembled in series. Two separate stock tanks are used for fertilizer application.

Dosatron injectors assembled in series inject fertilizer from two separate stock tanks

 

 

Macronutrients  (ppm in final solution)

N : 80 ppm P : 50 ppm, K : 85 ppm Ca : 95-100 ppm, Mg : 40 ppm, S : 56 ppm,

 

Micronutrients  (ppm in final solution)

Fe : 2.8 ppm, B : 0.6 ppm, Mn : 0.4 ppm, Cu : 0.1 ppm, Zn : 0.2 ppm, Mo : 0.03 ppm

 

pH ~ 6.0 – 6.2  and E.C. ~ 1.4 – 1.6 mS/cm

 

HEATING

Diesel heaters (Sundair Inc.) are operated to maintain a base minimum temperature of 3-5°C on days with sub-zero temperatures.

 

POLLINATION

Strawberry is mostly self-pollinated, and under field conditions, self-pollination is supplemented with natural agents like wind, honey bees, and other insects. However, under greenhouse conditions, the activity of these natural agents is highly restricted by the protective structure and the use of bumble bees is absolutely essential to ensure good pollination. One beehive (Koppert Biological Systems Inc.) containing approximately 50 bumblebees is sufficient for pollinating about 4,000 strawberry plants (500 m² greenhouse area).

                                             Bumblebee pollinating a strawberry flower

 

 

BIOLOGICAL CONTROL OF GREENHOUSE STRAWBERRY PESTS

 

Biological pest control is an important part of integrated pest management of greenhouse strawberry pests. We use various species of beneficial insects to control pests like the cotton aphid (Aphis gossypi), the green peach aphid (Myzus persicae), the two-spotted spider mite (Tetranichus urticae), and the western flower thrips (Frankliniella occidentalis).

 

Coleomegilla maculata (Ladybug beetle) adults and larvae (Entomos L.L.C., FL) are used for controlling aphids and mites. C. maculata has a Life cycle of 18 days from the egg to the adult stage and adult beetles can survive for 3-6 months. The larvae can consume 10-15 aphids per day.

                                   Ladybug beetle (Coleomegilla maculata)

 

                                                                                                                                                 

Aphidius colemani (Parasitic wasp) adults (Syngenta Inc) parasitize aphids and provide excellent control if released early in the season before the aphid populations start increasing. Life cycle from the egg to adult stage is 14 days. Adults can live for 2-3 weeks and parasitize about 100-200 aphids per day.

 

                                    Aphidius colemani  wasps parasitize adult aphids 

 

 

 

 

Geocoris punctipes (Big-eyed bug) nymphs (Entomos L.L.C., FL) are used to control aphids and mites. 

G. punctipes has a life cycle of 30 days from the egg to the adult stage, and life span of adults is 2-4 months. They can consume about 10-15 aphids and 45-50 mites per day.

 

Orius insidiosus (Insidiosus Flower Bug) adults (Entomos L.L.C., FL) are used to control mites and thrips.

O. insidiosus has a life cycle of 12 days from the egg to the adult stage. Adults can survive for 35 days and can consume about 30 mites per day.

 

Neoseiulus californicus (predatory mite) adults (Syngenta Inc.) feed on two-spotted spider mite adults and eggs. Life cycle of N. californicus from the egg to adult stage is 1-2 weeks and they can consume one adult and a few eggs per day.

 

Bacillus thurengiensis  var. israelensis is applied every two weeks through the fertilizer injectors for controlling fungus gnats.

 

Powdery mildew [Sphaerotheca macularis (Wallr. Fr.) Jacz. f. sp. fragariae, Peries] infects strawberry flowers and fruits in all stages of development and is especially severe in Florida from November through March.

A biofungicide called AQ-10 (Ampleomyces quisqualis) is used for controlling this disease.