Raspberry

Description

Raspberry is the name given to two plant species in the genus Rubus, Rubus idaeus (red raspberry) and Rubus occidentalis (black raspberry) grown for their edible fruit. Raspberry plants have perennial root systems and biennial stems which are known as canes. The canes are woody, erect and shrub-like and generally undergo a period of growth one year and fruit production the next although primocane varieties exist that produce fruit in the first year. The canes may possess spines. Raspberry plants produce white or pink flowers with five petals which are surrounded by green sepals. After the plant has been pollinated, an aggregate berry is produced which consists of numerous druplets which are held together into the familiar raspberry fruit by tiny hairs. Raspberry canes can grow from 0.5 to in excess of 2 m (1.6–6.6 ft) in height and red raspberry will produce a commercial yield of fruit for 16–20 years, while black raspberry has a shorter lifespan and will produce for 4–8 years. Red raspberry may also be referred to as European raspberry, red garden raspberry or hindberry, while black raspberry may be referred to as blackcap raspberry and may have originated in the Ide mountains of Turkey.


Uses

Raspberries are primarily consumed as a fresh fruit or may be processed into jams, jellies, juices and pulp.


Propagation


Requirements
Raspberry plants grow best in regions with cool summers and relatively mild winters. The plants are sensitive to high temperatures and grow best when daytime temperatures are around 25°C (77°F). Raspberries are best suited to well-draining sandy loams, rich in organic matter and have a pH between 5.5 and 6.5. Drainage it critical in raspberry propagation as the plants are susceptible to root rot. Plants require full sunlight and should not be planted in low lying areas where water may build up. Raspberries also require a post support system or trellis to support the weight of the fruit on the canes. Raspberry canes are biennial and produce fruit in the second year of growth. Canes in their first year of growth are called primocanes and those in the second year of growth are called fruiting canes or floricanes. The young canes are green in color, whereas the older floricanes are tougher and have a woody covering making them easy to tell apart.

Preparation
Soil may need prepared up to two years in advance of planting if major amendments are required. Acidic soil can be amended with lime to bring the pH up to a level suitable for raspberries. Organic content can be increased by planting a cover crop or by the addition of manure or compost. Avoid planting raspberries where peppers, eggplant, tomatoes or potatoes have been grown previously as these plants are host to Verticillium fungi which can cause root rot in raspberries. Choose a raspberry variety which is suited to your region. Red raspberries tend to be the most cold hardy, whereas black or yellow varieties are more sensitive.

Planting and trellising
Many raspberry varieties are very vigorous and using a support system such as a trellis will help to protect the canes from wind damage while also supporting the weight of the fruit crop. The trellis should be constructed before or at planting to avoid damaging the young plants after they are in the ground. The traditional method of supporting red raspberry canes is a post and wire system. This method involves running two wires about 60 cm (2 ft) apart vertically between wooden posts staked into the ground. The lower wire should be positioned 90 cm (3 ft) from the ground and the upper 1.5 m (5 ft) from the ground. The raspberry canes can then be tied to the wires. A second option is a T-trellis which is similar to the post and wire but the vertical wooden posts each have two cross bars to attach the wire. Two sets of wires run parallel to one another, one above the other. The vertical posts should be spaced 3.6–4.6 m (12-15 ft) apart with the lower wire positioned 90 cm (3 ft) from the ground and the upper 1.5 m (5 ft) from the ground. Raspberry plants in the home garden are usually grown from bare root plants or from tissue-cultured plants and should be planted in early Spring when the danger of any severe frosts has passed. The plants are usually planted in a row and the suckers will fill in the spaces to produce a hedge. Plant approximately 70 cm (27.5 in) apart, allowing 2.4–3 m (8–10 ft) between rows.

Pruning
Allow the raspberry plants to fill in the row to a width of about 30–38 cm (12–15 in) during the course of the growing season. Remove any suckers which are produced outwith this row. After harvest, cut the fruited canes of summer-fruiting varieties to ground level. Select 6–8 of the strongest young canes on each plant and tie them to the supporting wires so that they are spaced 8–10 cm (3–4 in) apart. Cut all of the canes of Autumn fruiting varieties to ground level after harvest. Cut back canes as needed in the summer if required to prevent crowding.


References

CABI Crop Protection Compendium. (2014). Rubus idaeus (raspberry) datasheet. Available at: http://www.cabi.org/cpc/datasheet/48002. [Accessed 06 April 15]. Paid subscription required.

Ellis, M. A. & Converse, R. H. (Eds.) 1991. Compendium of raspberry and blackberry diseases and insects. American Phytopathological Society. APS Press.

Strick, B. C. (2008). growing raspberries in the home garden. Oregon State University Extension. Available at: http://ir.library.oregonstate.edu/xml.... [Accessed 06 April 15]. Free to access.


Common Pests and Diseases

Fire blight
Erwinia amylovora

Symptoms
The infected cane tip become blackened, bend over and die which resembles the “shepherd’s crook” appearance. The affected cane may ooze cream colored bacteria under high humid conditions. If the infection continues down the cane, the leaf veins and surrounding tissue of the midvein turn black. Later whole leaf may wither and die. The infected berries do not mature, become brown, dry up, become very hard and remain on pedicel. Generally the infection is restricted to young growth of the plant.
Cause
Bacterium
Comments
The pathogen is transmitted by wind, rain splash and insects.
Management
Use healthy and disease free seed materials. Remove and burn the infected parts.

Spur blight
Didymella applanata

Symptoms
Purple-brown lesions on the stem just under the leaf or bud; lesions are usually on the lower portion of the stem; bark splitting on canes lengthways; brown triangular lesions may form on edges of leaves.
Cause
Fungus
Comments
Fungus is able to overwinter on diseased canes and disperse during rainfall and active wind.
Management
Increase air circulation within the canopy by reducing the frequency of periods of leaf wetness (avoid overhead irrigation where possible) and thinning plants to reduce crowding; avoid excessive application of fertilizer, particularly nitrogen; practice good weed management; if disease is severe then an an application of appropriate fungicide may be merited.

Cane blight
Leptosphaeria coniothyrium

Symptoms
Purple black cankers form at wounds on young canes; cankers enlarge to encircle cane and cause wilting and death of lateral shoots; infected canes are often cracked and brittle, breaking easily; black specks (fungal fruiting bodies) may become visible in the cankers.
Cause
Fungus
Comments
Spread by rain splash from infected to healthy canes.
Management
Always plant raspberries in full sun and in an area with good drainage; plant only certified planting material; avoid over fertilizing plants; remove and destroy fruiting canes immediately after harvest; if pruning is necessary then make cuts during dry weather to allow wounds to heal before wet weather; control insect pests which may cause wounds to the canes such as crown borers and stem girdlers.

Gray mold
Botrytis cinerea

Symptoms
Blasting symptoms (browning and drying) of one, or a cluster, of blossoms; soft, light brown areas on fruits which enlarge rapidly; berries become mummified and is covered in a gray powdery substance;
Cause
Fungus
Comments
Disease emergence favors high moisture and slow drying areas.
Management
Always plant raspberries in full sun and in an area with good drainage; plant only certified planting material; avoid over fertilizing plants; remove and destroy fruiting canes immediately after harvest; practice good weed management around the raspberry canes; harvest fruit frequently and during dry weather; remove and destroy diseased berries to reduce inoculum.

Yellow rust
Phragmidium rubi-ideai

Symptoms
Yellow-orange pustules on underside of leaves; premature death of leaves, increased cold weather injury.
Cause
Fungus
Comments
Pathogen is not systemic and will not spread within the plant; spores are transmitted by wind.
Management
Improve air circulation around the plants by pruning; removal of entire floricane and the first flush of growth on the primocane can greatly reduce the amount of inoculum but is not alwasy economically feasible; growing raspberries in tunnels can greatly reduce incidence of disease if plants are protected before conditions are favorable to the rust pathogen.

Raspberry leaf spot
Sphaerulina rubi

Symptoms
The symptoms appear on young leaves as small dark green circular spots. As the disease progress the spots become light tan to gray color. Later the infected tissue may fall out. Severely infected leaves may fall off prematurely.
Cause
Fungus
Comments
Spores are spread by splashing water.
Management
Remove infected crop debris and burn them. Provide proper air circulation around the plant. If the disease is severe, spray suitable fungicide.

Weevils (Black vine weevil, Strawberry weevil, Clay-colored weevil)
Otiorhynchus spp.

Symptoms
Large notches chewed in leaves; reduced plant vigor and development; feeding damage to roots .
Cause
Insect
Comments
Adult stage coincides with harvest; hides in fruit; larvae feed on roots.
Management
Hand pick weevils from plants; adult beetles are nocturnal and hide in plant foliage during the day; chemical control can be difficult and invloves spraying foliage or drenching soil with appropriate insecticides.

Phytophthora root rot
Phytophthora fragariae

Symptoms
Canes show a lack of vigor and reduced stand; symptoms often more apparent in low lying areas of field or in 'dips' within rows; leaves on affected canes may take on a yellow, reddish or orange tinge and have scorched leaf edges; canes which appear healthy may suddenly decline and collapse; infection can be confirmed by inspection of roots - infected plants will exhibit a characteristic brick red discoloration on scraping away the outer root surface.
Cause
Oomycete
Comments
Soilborne disease; emergence favors wet soil conditions.
Management
Once the disease has been introduced to a field then there is no method of treatment; good sanitation practices are important for preventing the introduction of the fungus into the plantation; always plant raspberries in well-draining soils or raised beds; one of the most effective methods of preventing the disease is to plant raspberry varieties which are resistant to the disease.

Leaf curl
Raspberry leaf curl virus (RLCV)

Symptoms
Leaflets small and rounded with margins curving downward and inward; new shoots yellowish, stiff, brittle, and shorter than previous year.
Cause
Virus
Comments
Transmitted by aphids.

Raspberry ringspot:
TomRSV

Symptoms
Yellow rings on leaves; yellow leaf veins; delayed leaf development; yellowing of canes; poorly formed fruit.
Cause
Virus
Comments
Spread by several species of nematodes.

Raspberry bushy dwarf
Raspberry bushy dwarf virus (RBDV)

Symptoms
Yellowing leaves; reduction in cane height; crumbly fruit; reduced plant vigor.
Cause
Virus
Comments
Symptoms are not consistent from year to year; virus is transmitted through pollen.

Raspberry mosaic disease
Black raspberry necrosis virus (BRNV)
Raspberry leaf mottle virus (RLMV)
Rubus yellow net virus (RYNV)

Symptoms
Short, fragile canes; mottled, puckered, upwardly arching leaves; green blister on leaves; downward curling leaves; yellow mottling.
Cause
Virus complex
Comments
Transmitted by aphids.