Cucumbers

Photo Credit: Stockbyte Florida Fresh

Key Factswiki_pendingPPOD_Cucumber_2

  • The top three countries that imported cucumbers to the United States in 2013 were Mexico (1,144,458,000 Ibs) Canada (215,028,000 lbs) and Honduras (65,244,000 lbs).
  • In 2012, top cucumber producing states, as reported by the United States Department of Agriculture, were Georgia and Florida with 283.5 and 280.8 million pounds, respectively.
  • There are three growing seasons in South Florida for field planted cucumbers; the fall season is from September to October, the winter season is from November to December, and the spring season is from January to March.
  • In the United States from 1998 to 2013, there were ten reported outbreaks associated with cucumbers, and 483 people fell ill. The pathogens implicated in these outbreaks were enteropathogenic E.coli, norovirus genogroup I and II, and Salmonella Saintpaul.

Introduction

The cucumber plant (Cucumis sativus) belongs to the Cucurbitaceae family, a part of the Cucumis genus. The Cucumis genus contains nearly 40 species, such as the cantaloupe (C. melo), and watermelon (Citrullus vulgaris). The cucumber has many common names including pepino, cetriolo, gherkin, gurke, krastavac, concombre, hunggua, kiukaba, khira, kiukamupa, and kukamba.

Cucumis sativus is a frost sensitive annual, coarse (large, bold, and rough leaves) and, creeping vine that can reach upwards of six feet in length. The spiraling hairy vine and tendrils that originate from the axil, allows the plant to readily climb supporting structures. Hairy three to five lobed leaves with a triangular shape that are 10 – 40 cm in size are each supported on a petiole and provide a canopy to cover the flowers and fruit. The overall root system is generally shallow (usually penetrates top 30 cm of soil) with lateral roots extending further than the vine; however, a tap root can reach one meter deep.,

The cucumber plant produces three types of rough yellow flowers including a male or staminate flower, a female or pistillate flower, and a hermaphrodite flower with both male and female structures. The pistillate flower can be recognized from its’ thin pedicles and it has a large ovary (immature fruit) at its’ base. The ovary has three chambers and is connected to short, thick stigma lobes. The staminate flower grows in clusters and each flower is on a slender stem having three stamens. Hermaphroditic flowers are able to produce round fruits. Regardless of the sex, the flowers are yellow with wrinkled petals.,,

Cucumber plants are naturally monoecious, meaning there are separate male and female flowers on the same plant. Gynoecious predominately produce female flowers’, however they will produce male flowers under conditions that include longer days, high temperatures and with light intense days. The seeds of both monoecious and gynoeccious maybe mixed for planting in the same area. Pollen is transferred by bees and other insects from the male to female flower. On commercial farms, gynoecious hybrids are more frequently used as they are more productive and develop earlier.

The cucumbers’ fruit has a hard, thick, firm outer rind, while being round, triangular-shaped, and is known as a false berry. The fruit goes through two stages, immature and mature. During its’ immature stage chlorophyll in the cells located under the epidermis makes the rind green in color. In the mature stage, the rind changes into a yellow-white color and the epidermal layer may develop warty areas that form a trichome (spiky hair). The fruit has three locules that contain soft tissue, and where the seeds are embedded. The cucumber fruit ranges in colors from yellow, orange, white, and green. A regular cucumber contains seeds and can also be referred to as a seeded cucumber. Regular cucumbers have green stripes on a dark green skin with a rough surface including strong trichomes. They are about 15-25 cm in length and uniformly cylindrical. English cucumbers are evenly green throughout, and long in length about 25-50 cm. The English cucumber is cylindrical in shape with a short narrow neck at the end of the stem and contains either atrophic seeds that are barely identifiable or no seeds.

The cucumber plant is native to India and has been cultivated for more than 3000 years. In the United States, the volume of cucumbers pickled is higher than any other vegetable; with 550,000 metric tons being produced each year. The 2012, United States Department of Agriculture data, showed the state of Georgia producing more cucumbers than any other state in the United States with producing 283.5 million pounds of cucumbers. Florida followed producing 280.8 million pounds of cucumbers. The most prominent area in Florida producing cucumbers is the west-central region including counties of Hillsborough, Manatee, and Hardee.

Photo Credit: (scotsburn.blogspot.com) Burpless cucumber
Burpless cucumber. Photo

Common Varieties

Cucumbers are commonly grouped into three types: burpless, slicing, and pickling. Greenhouse cucumbers are also classified as a cucumber cultivar and can be included into this list. The information below will provide you with a brief guide on common cucumber types.

Burpless

This cucumber has a milder taste and contains less of the burp-causing compound called cucurbitacin. Burpless cucumbers are long and slender with tender skin and available year round.

The Asian cucumber, a sub variety of the burpless type has a dark green color with semi-rough skin and is 10 to 14 inches long; usually thin and straight. The taste is milder flavor than standard types.,

Photo Credit: (newrootsforrefugees.blogspot.com) Asian cucumber
Asian cucumber. Photo
Slicing

The slicing or fresh market cucumber is usually 8 – 9 inches with blocky ends and small yellow ground spots on a thick dark green skin. The thick skin makes this type of cucumber have the benefit of being less prone to damages during harvest. Slicing cucumbers are considered semi-dwarf. The plant only requires 2 feet of space for growth and is resistant to powdery mildew, anthracnose, cucumber mosaic virus, downy mildew, scab, angular leaf spot. Both monoecious and gynoecious hybrids are available.

Regular cucumbers are American cucumbers, belonging to the sub-variety of the slicing cucumber. They are usually 8 inches long with a slight bulge in the middle. After harvest, they are waxed to improve their moisture retention as well as the shelf life. The seeds are larger and more plentiful than other varieties.  Photo Credit: Brialle Brewton, English cucumbers sold at Action in Beauvais, France.

Photo Credit: Brialle Brewton, English cucumbers sold at Action in Beauvais, France.
English cucumbers for sale in at an outdoor market in Beauvais, France. Photo: Brialle Brewton
Pickling

These cucumbers typically have a warty, thin, usually light green color skin with the fruit size ranging from 3-7 inches. Maturation can take up to 50-60 days. Commercial cultivars have black or white spines that form as the fruit matures. The white-spined cultivars compared to the black-spined cultivars are usually slower in development, but unlike the black-spined fruit they are able to retain their green color and firmness of their skin longer. The premature black-spined cultivars turn yellow at higher temperatures. Both cultivars are used in the pickling industry. The white-spined cultivars are predominately used in the warmer seasons with mechanical harvesting; whereas as black-spined cultivars are grown in regions that experience cool summer conditions.,

The skin of the Kirby cucumber is thin, bumpy, and color varies from light to dark green. This cucumber is a sub-variety in pickling cucumbers.

Photo Credit: larkenspringsfarm.com Kirby cucumber
Kirby cucumber. Photo

It is smaller in size growing 3 – 6 inches long, they often grow in an irregular shape. The flavor it produces is mild to sour.

The Gherkin cucumber size is smaller than the other types, and has a long distinctive fruit stem. The color ranges from a light yellow to pale green and the fruit is covered in short fleshy spines. The taste of the West Indian Gherkin is sweet at first then turns sour.

The Bush Pickle produces 4 inch fruits that are deep green in color with pale green stripes and a blocky figure having that distinguished “pickle” look. Maturation takes place in 55 days.

 Photo Credit: www.clovegarden.com Armenian cucumber
Armenian cucumber. Photo

Armenian cucumbers are actually members of the melon family and known as the ‘snake cucumber’, the Armenian cucumber fruit is 12 to 15 inches in length with thin pale green skin.,

Greenhouse cultivars

The appearance of greenhouse cultivars are usually smooth-skinned with rounded ends, and are long and narrow. There are two types of greenhouse cultivars, English and Japanese. The Japanese cucumbers taste is never bitter, and flavors are melon-like. The English types have a high yield potential and are parthenocarpic (fruit being produced without presence of an egg in the ovary) with gynoecious expression, which are different from the Japanese types that are primarily monoecious.,

For more information regarding the production and distribution of Cucumbers please visit the Produce Point of Origin Database.

Foodborne Outbreaks

From 1998-2013 in the United States, there have been a total of 10 cucumber associated outbreaks, during which 483 people became ill and eight were hospitalized. Cucumber salad, cucumber sandwiches and raw cucumbers are among the implicated food items. The setting where these outbreaks occurred included private homes, restaurants, conferences, and hotels.

In 2013, an outbreak of Salmonella Saintpaul was linked to imported cucumbers from Mexico. This outbreak caused 84 people to become ill with 17 hospitalizations. On April 24, 2013, importation of cucumbers was shut down by The U.S. Food and Drug Administration; two trading firms were placed on import alert for cucumbers. These two firms had to prove the cucumbers they were importing into the United States were Salmonella- free to have the import alert lifted.

To contribute to the Cucumber-associated Foodborne Outbreaks section, please follow this link: http://fsi.colostate.edu/suggest-a-topic/

Production

Planting

With greenhouse types of cucumbers, the growth period lasts from 55-60 days. The primary method for cucumber planting is direct seeding. The row’s width should be 3 -4 feet, with a 4 -8 inch distance between plants in the row and the depth of the seeds 1- 1 ½ inches. Close proximity of plants will increase the yield, reduce weed growth, and keep the maturity rate uniform.

Cucumbers are sensitive to growing conditions. Favorable growing conditions for a cucumber are similar to a semitropical plant in that humidity, high temperatures, intensity of light, and constant water and nutrient supply, are all necessary. Under these conditions with proper pest management, the plants have an opportunity to grow fast and produce heavy yield. Frequent pruning of the stems, laterals, and tendrils as well as vertical wire training is needed in order to uphold a canopy that allows the maximum amount of light and air to the plant and will allow for maximum yield. When the plant produces too many fruit it can cause the plant to become exhausted and abort future fruit.

Air temperature impacts vegetative growth, flower initiation, fruit development and quality. Optimum growing night temperatures range from 66.2-68 degrees Fahrenheit and optimum day temperatures range from 68-71.6 degrees Fahrenheit.

Regulation of greenhouse conditions is important to maximize yield. A disadvantage with high relative humidity is that diseases can develop and there is an increased chance that water condensation could occur on the plants. With low relative humidity the conditions favor formation of powdery mildew and allow spider mites to reside. The irrigation system is a critical component because large amounts of water must be provided to the growing medium without flooding its roots and depriving them of oxygen.

The trellis saves space and is used to increase air circulation, helping to decrease risk of disease; it also serves as a way to protect the cucumber from developing damage due to moisture from lying on the ground.,

Cucumbers grown in Florida have a long harvest season when field grown. In North Florida, field grown cucumbers are planted from February to April and August to September. In Central Florida the planting season is from January to March and September for the fall season. For the Southern region of Florida planting can commence anytime from September to April. Greenhouse production in Florida is usually done September through June. Planting in greenhouses in summer months’ are avoided due to high heat and humidity, which reduces the plant’s production.

The type of soils used in growing cucumbers varies. Some acidic soils can be used but they need liming and fertilization done before the seeds are planted. Cucumbers grow best in slightly acidic soils with a pH range of 5.8-6.5. The soil should be properly prepared before field planting begins. Common steps include soil fumigation, black plastic mulching, applying fertilizer during bed preparation, using foil or other reflective mulches for repelling aphids, and applying direct seeding throughout the mulch. Cucumber seedlings develop faster in higher temperatures, but cucumber growth is improved when soil temperatures are cooler.

Nearly all greenhouse production of cucumbers in Florida use bag culture and perlite as the medium. Rockwell could also be used as a medium.  Greenhouse cucumbers do best in soil with a pH range of 5.5-7.5, but specifically for mineral soils the pH range must be from 6.0-6.5. As for organic soils in greenhouse production, the optimum pH level must range from 5.0-5.5. 

Different varieties of cucumbers are able to cross pollinate with each other. A pollen grain is needed for each seed within each cucumber. Without proper pollination the fruit could be aborted, disfigured, or be a poor fruit set (transition of an ovary to a young fruit). Proper pollination hives should be brought to the field when 25% of the plants in the field have flowered. A single flower needs to be visited by bees 10-20 times to be pollinated. If the bees are brought into the fields before 25% of the plants have flowered the bees could be attracted to other food sources such as wildflowers, therefore reducing yield. When bringing hives to the fields the weather should not be cool, or wet as these conditions are unfavorable for bees, the weather causes the bees to be less active and the outcome is poor fruit sets.

Soil and Amendments

Photo Credit: http://publicphoto.org/plants/young-cucumber-plant/ After germination.
Cucumber plan after germination. Photo Credit: http://publicphoto.org/plants/young-cucumber-plant/

Cucumbers are well grown in muck soil, but can be produced in sandy soils as well, which requires less cleaning before marketing.

In cucumber production soil amendments are used for improvement of soil quality. Composted green waste or manure can be added to soils before planting begins and this helps to increase the holding capacity for water, and supply nutrients to the crop. Farmers must be careful where they purchase the manure from since traces of E.coli can be found, it is best to look into commercially composted manure. Soil mulches are commonly used to modify soil properties such as temperature, weed control, conserving water, protection fruit from insects, soil moisture, and control erosion. There are nutrients that farmers choose to use during the process of producing cucumbers. The primary nutrients used are nitrogen, potassium, phosphate and the secondary nutrients are considered magnesium, calcium, and sulfur. For cucumbers that are grown on mulch that are polyethylene free, reductions of up to one half of the nitrogen and potassium fertilizer are applied at planting.

Irrigation

Many irrigation systems successfully produce good production results. Different irrigation systems are used and the type is based on technology, natural resources, cost and benefits. Drip, sprinkler, and surface are types of irrigations systems used with mulched production. Drip irrigation uses a variety of plastic pipes to carry a low flow of water under low pressure to plants. The low volume application of water to plant roots allows for a balance of air and water in the soil, providing plants with better growth. Sprinkler irrigation systems are different from the other systems because it applies water through the air versus directly in the soil. The water can be distributed through a pipe or sprinkler head and is sprayed into the air and falls on the ground similar to rainfall. Surface irrigation systems distribute water by gravity flow of water going over the soils’ surface. As this occurs the soil stores the water and the system acts as a medium spreading and infiltrating the water.

Some greenhouse cucumbers are irrigated using a closed irrigation technique or drain-to-waste irrigation. Common sources of water for irrigation are ground, surface, or potable waters. The water’s pH is important in an irrigation system, the recommended optimum pH of the nutrient (nitric, sulfuric, and phosphoric acid) solution that is applied to the plants through the irrigation system should range in between 5.5-6.0. These conditions vary if the water has a high bicarbonate concentration, which prevents precipitation when fertilizer salts are added.

The cucumber is sensitive during its growing process, being sensitive can affect its quality and yield such as salinity, perchlorate, chloride, and glyphosphate toxicity. Salinity can cause the plant growth to be stunted and cause leaves to have the appearance of the cucumber a dull, dark green color with a narrow band of yellow nercrotic tissue around the leaves that are prone to wilting. Studies have demonstrated that with the increase of salt in the water there is a decrease in cucumber yield.

Chloride when added to water used in the irrigation system showed the reduction of plant vigor and produced a light green tissue band around the leaves margins, along with necrosis and edge scorching. These leaves are at risk for a reduction in photosynthesis activity and premature leaf abscission.

Perchlorate is a strong acid and is available in mineral deposits of natural nitrates. Due to its strong chemical properties it decreases the Ribulose Diphosphate Carboxylase (RuDP) enzyme activity used for cultivation in greenhouse vegetables. The symptoms that follow exposure to high concentrations of perchlorate include female flowers beginning to open, leaves curled with partial necrosis causing a reduction in fruit sets which in turn reduced yields, and dysfunctional cucumbers.

Pests & Insecticides

Photo Credit: James Castner, Entomology and Nematology Department, University of Florida. The spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber
The spotted cucumber beetle, Diabrotica undecimpunctata howardi Barber. Photo Credit: James Castner, Entomology and Nematology Department, University of Florida.

Pesticides are used in the cucumber production process to help decrease the impact of insects on the plant. There is a range of insects that can attack cucumbers, but the major insects that are prominent in Florida are the pickleworm, melonworm, and silverleaf whitefly. In cucumber greenhouse production the major pest are the whiteflies. Other insects to impact production outside of greenhouse are arthropods as melon thrips, leafminers, banded cucumber beetle, flea beetles, mites, stink bugs, wireworms, grasshoppers, leafhoppers, squash bug, squash vine borer, and loopers. These pests may not cause serious damage of the cucumber but they are a serious concern for the grower due to the very low tolerance for insect damage in the crop. The cucumber beetle is comprised of six different species across the United States. Three of these beetles are found in Florida. The banded cucumber beetle is located in the southern part of Florida. The spotted cucumber beetle and striped beetle are found in North Florida.

Photo Credit: John L. Capinera, University of Florida, Pickleworm, Diaphania nitidalis, larva feeding inside cucumber fruit.
Pickleworm, Diaphania nitidalis, larva feeding inside a cucumber. Photo Credit: John L. Capinera, University of Florida.

The cucumber beetles larvae begin damage by eating away at the plant from the roots to the stems. As an adult host they eat away at the stems that are below the plastic mulch, as well as the leaves, and the fruit. The crop is damaged quickly by feeding on the cotyledons first and then moving to foliage. Crop damage from these beetles often transmits Erwinia tracheiphila, the causal agent of bacterial wilt. The squash mosaic virus can also be transmitted and the increase of incidence of powdery mildew, black rot and fusarium wilt.

Insecticides are typically used to combat bacterial wilt. As for the squash mosaic virus, which is transmitted by insects, once the plant is infected it must be removed so that it does not infect the other plants. There are preventative measures that can be taken to try to avoid the occurrence of the virus such as controlling the weeds.

In 2000, Florida growers applied insecticides totaling 15,500 pounds of active ingredient to 97 percent of the state’s fresh-market cucumber acreage. Annually between 94-97 percent of fresh market cucumber acreage has been treated with insecticides and the most commonly applied insecticides on Florida fresh-market cucumbers are Bacillus Thuringiensis, Methomyl (Lannate®), and Endosulfan a cyclodiene chlorinated hydrocarbon insecticide.

Disease Prevention

There are a few techniques that are used to help lessen the chance of the cucumber encountering disease. For commercial growers, Utilizing certified disease-free seeds, keeping the garden and surrounding area free of weeds that harbor insects, which can spread viruses and bacterial wilt, and once harvesting is complete remove the plant debris that is left behind in the garden, this is because some diseases have the ability to survive on plant debris. An important measure in controlling disease is host resistance. The types of diseases that can affect cucumbers are gummy stem blight, which is a leaf disease caused by the fungus Didymella bryoniae, Anthracnose caused by the fungus Colletotrichum obiculare, Fusarium wilt caused by the fungus Fusarium oxysporum, Downy mildew (favored in moist conditions) causedby the fungus Pseudoperonospora cubensis.

Glyphosphate is a herbicide that even in small amounts being absorbed by the cucumber will cause damages such as turning the color of the leaves from light green to a yellow, stunt the growth, and cause upwards curling.

Fungicides are most useful when they are applied prior to infection and must be reapplied once the infection occurs every 5 to 7 days. Some examples of the types of fungicides used are Previcur Flex, Gavel, Tanos, and Ranman.

Harvesting, Packaging, and Storage

The harvesting process can be done by hand or machine and is different depending on the cucumber. The following videos will show different harvesting techniques used in growing cucumbers.

Greenhouse Cucumbers:

Harvesting Machines:

Cucumbers should be picked when crisp, green, and tender; large fruits should be removed from the vine so that new fruits are encouraged to grow. Slicing cucumbers are hand harvested at a range of 6-10 inches long and 1.5-2.5 inches in diameter. They usually are picked over a three-week time frame, 6 to 8 times. Pickling cucumbers are generally harvested 5 to 6 times, in 3 to 4 intervals to avoid oversizing. Gherkin cucumbers are harvested daily or every other day based on the weather and the stage of growth.,

Photo Credit: Melisa F. Crane and Todd C. Wehner
Workers tending to cucumber plants. Photo Credit: Melisa F. Crane and Todd C. Wehner

Fresh-market cucumbers and European types they are hand harvested and placed in plastic bins to be transported to the packing-house. Once the cucumbers have reached the packing house they are washed, sorted, and graded. Since the fresh market cucumbers are prone to extreme dryness, they are waxed prior to being packed again to help with reducing water loss and skin injury. As for greenhouse cucumbers, most are shrink-wrapped with polyethylene films.

During storage cucumbers should not be stored with produce that generate ethylene. Common produce that produces ethylene are: apples and tomatoes. The ethylene causes the cucumber to become yellow rapidly from the loss of chlorophyll. For the best postharvest results including a long shelf-life, cucumbers should be stored at a temperature ranging from 44.6-50 degrees Fahrenheit and 85-95% relative humidity in air, 46.4-53.6 degrees Fahrenheit in1-4% oxygen and 50-54.5 degrees Fahrenheit in 0% carbon dioxide.

Photo Credit: Cucumber production (slides), 1979 North Carolina State University College of Agriculture and Life Sciences
Cucumbers planted in a field. Photo Credit: Cucumber production (slides), 1979 North Carolina State University College of Agriculture and Life Sciences

Cucumbers can go through a pickling process; the fermentation of cucumbers can be performed in three general methods. One way is by ‘salt shock’ in which cucumbers are preserved in 5-8% sodium chloride until the fermented sugars are converted to acids, increasing the salt concentration along the process. The second method is known as the ‘genuine dill’, the cucumber is fermented in 45% sodium chloride, flavor is added then the cucumber is sold as is. The ‘overnight dill’ is the third method performed by fermenting 2-4% sodium chloride containing dill weed and garlic, the fermentation continues until it reaches the desired acidity then its’ refrigerated.

Food Safety

To contribute to the Cucumber Food Safety section, please follow this link: http://fsi.colostate.edu/suggest-a-topic/

Consumption

From 1995-2005, there was a 15% growth in the consumption of fresh cucumbers, an approximately 1 pound per capita increase. As of 2012, Americans consumed an average of 6.5 pounds of fresh cucumbers per person. For pickled cucumber, Americans annually consume a more variable amount averaging 9-11 pounds per person. From the 2006-2007 FoodNet Atlas of Exposures, 46.9% of the survey cohort reported eating cucumbers within the past 7 days.

Nutrition 

Cucumbers are 90-95 percent water and have limited nutritional value compared to other vegetables because of this. In one serving of cucumbers there are about 45 calories along with the daily recommended intake; 6% of Vitamin A and Vitamin B6, and 14% Vitamin C. The cucumber can aid in alleviating irritation and sunburn similarly to the aloe plant by applying the sliced cucumbers to the affected area. The slices can also reduce puffiness under the eyes (also known as “bags” under the eyes) since it has anti-inflammatory properties and stimulates hair growth. Being rich in vitamin A, B1, B6, C, & D, Magnesium, Folate, Calcium, and Potassium, cucumbers contain a good source of silica that allows the connective tissue to be strengthened while promoting healthy joints. Cucumbers contain three lignans: lariciresinol, pinoresinol, and secoisolariciresinol, all of which have traits of reducing the risk of developing several cancers such as breast cancer, ovarian cancer, uterine cancer and prostate cancer.

References

Author

Brialle Brewton
Food Science Undergraduate Student
Florida Agricultural & Mechanical University

Editors

Benjamin G. Klekamp, MSPH, CPH
Liaison, Florida Integrated Food Safety Center of Excellence (Until April 2014)
Florida Department of Health

David Dekevich, MPH
Liaison, Florida Integrated Food Safety Center of Excellence
Florida Department of Health

Jamie DeMent, MNS
Coordinator, Food & Waterborne Disease Program
Florida Department of Health

 

Author

David Dekevich

David Dekevich

Florida Integrated Food Safety Center of Excellence Liaison at the Florida Department of Health

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