Blueberry

Description

Blueberry is a crown forming, woody, perennial shrub in the family Ericaceae grown for its fruits, or berries, of the same name. The blueberry plant possesses oval or elliptical leaves which grow alternately on the stems. The stems, or twigs, are yellow/green in color and turn reddish in winter. Flowers are bell shaped and can be either white or pink, occurring in clusters of 8 to 10 flowers. Berries are blue to black in color and 0.6–1.3 cm (0.25–0.5 in) in size. Lowbush blueberry plants (including Vaccinium angustifolium) are smaller in stature, reaching heights of 35 to 60 cm (13.8–23.6 in) and with proper management can produce fruit for between 40 and 50 years. Lowbush blueberries are also sometimes referred to as Maine, New Hampshire or wild blueberry and are native to eastern/central Canada and northeastern United States. Highbush blueberries (including Vaccinium corymbosum) are generally 2–3 m (6.6–9.8 ft) in height but can reach up to 5 m (16.4 ft) and may also be referred to as huckleberry or swamp blueberry. Highbush blueberry accounts for most of the commercial production of blueberry fruit and is also native only to North America.


Uses

Blueberries can be eaten fresh or can be dried or baked for further processing. Frozen or pureed berries are commonly used to make jams and preserves and baked goods. Lowbush blueberry is commonly used to make wine.


Propagation

Lowbush blueberry grows best in well-drained, acidic soils with a pH between 4.5 and 4.8 and should be planted in early Spring as purchased plants or as “plugs” (a small cutting, including root, from an established bush). The newly planted blueberry should be covered in a couple of inches of mulch to conserve moisture in the soil. Any flowers produced by the plants should be removed for at least one year after planting to promote vigor and new growth. Plants should be pruned by cutting close to the ground and a pruned plant will not produce any fruit in the first year, but in the second year subsequent to pruning their should be a good yield. Growth can be stimulated by field-burning, as these plants are very fire-tolerant.

Highbush blueberry can be propagated from seeds, cuttings from an established plant or bare root and should be planted in late Fall. Blueberry plants grow best in well drained, highly acidic soils with a pH between 4.5 and 5.8. The plants have a shallow root system and should be planted in a hole at least twice as large as the existing root system and mulched with a 7-10 cm (3-4 in) layer of organic mulch. The first year of blossom should be removed to encourage new growth and it is also recommended to do the same in the second year. Plants should be pruned annually, particularly after the first two years, to promote plant vigour and remove diseased or broken canes. Irrigation is recommended due to the shallow root system and greatly promotes the fruit yield this practice is highly recommended if growing commercially.


References

CABI Crop Protection Compendium. (2008). Vaccinium datasheet. Available at: http://www.cabi.org/cpc/datasheet/55994. [Accessed 07 November 14]. Paid subscription required.

Caruso, F. L. & Ramsdell, D. C. (1995). Compendium of Blueberry and Cranberry Diseases. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.

Lord, W. (2001). Growing Highbush Blueberries. University of New Hampshire Cooperative Extension. Available at: http://extension.unh.edu/resources/fi.... [Accessed 07 November 14]/ Free to access.

Lord, W. (2013). Wild New Hampshire Blueberries. University of New Hampshire Cooperative Extension. Available at: http://extension.unh.edu/resources/fi.... [Accessed 07 November 14]/ Free to access.

Nelson, G. & Davis, K. (2002). Highbush Blueberry Vaccinium corymbosum L.. United States Department of Agriculture & Natural Resources Conservation Service Plant Fact Sheet. Available at: http://plants.usda.gov/factsheet/pdf/.... [Accessed 07 November 14]/ Free to access.


Common Pests and Diseases

Blueberry bud mite
Acalitus vaccinii

Symptoms
Blistered red scales on buds; misshapen flowers, small leaves and fruit; damage may lead to poor growth and yields; mites are microscopic and difficult to see with the naked eye
Cause
Arachnid
Comments
Mite eggs are laid in the bug scales and adult mites migrate down stem to feed
Management
Control of mites can be difficult as they are protected from pesticides by bud scales; miticides are most efffective when applied just after harvest when the buds have not yet formed as they are more exposed to the chemical

Mummy berry
Monilinia vaccinii-corymbosi

Symptoms
Drooping of new leaves and shoots in Spring; rapid browning of upper surface of affected shoots and leaf midribs and veins; death of infected shoots,leaves and flowers 24-72 hours after appearance of brown discoloration; after initial symptoms in Spring, plants become symptomless until fruit development; infected berries are cream or pink in color and turn tan or gray; berries become shriveled and hard; shriveled skin of fruit breaks down to expose black rind of fungal tissue
Cause
Fungus
Comments
Disease affects highbush, lowbush and rabbiteye blueberry varieties; bees can aid the transfer of the fungus from infected to healthy flowers
Management
Plant disease-free, dormant plants; remove or bury mummified fruit, if burying fruit cover with at least an inch of soil; application of appropriate foliar fungicides are very effective at controlling the disease in commercial plantations

Botrytis blossom blight (Gray mold)
Botrytis cinerea

Symptoms
Corollas of expanded blossoms appear blighted; brown lesions on leaves which have come into contact with infected blossoms; infected blossoms do not produce fruit; in large fields, severe infedctions are often visible as brown patches
Cause
Fungus
Comments
Can be very damaging to lowbush blueberries; fungus overwinters in fruits, stems and leaves of plant; disease emergence is favored by wet weather; severe outbreaks can occur after wet periods lasting several days or more
Management
Disease can be controlled by application of appropriate fungicides, if available, at mid-bloom and late bloom stage

Powdery mildew
Erysiphe vaccinii

Symptoms
White fluffy growth on upper surfaces of leaves or lower leaf surface; leaves may be puckered in appearance; leaves may develop chlorotic spots with red borders; leaves may drop from plant
Cause
Fungus
Comments
Disease emergence is favored by warm, dry conditions
Management
Plant resistant highbush blueberry varieties; apply appropriate foliar fungicides, if available

Stem canker
Botryosphaeria corticus

Symptoms
Initial symptoms appear as red lesions on green stems which become swollen and conical; on rabbiteye blueberry varieties lesions are initially brown sunken spots; in susceptible varieties lesions develop into large swollen cankers with deep cracks after 2-3 years of infection; if the variety is very susceptible the cankers may kill the stem
Cause
Fungus
Comments
Infection occurs in late Spring; spores are spread by wind; at lower temperatures the disease may be limited to small red flecks
Management
The most important method of controlling stem canker is to plant resistant varieties in areas where the disease occurs as fungicides are largely ineffective; no varieties of highbush blueberry are resistant to all strains of the disease; infected wood should not be used for propogation

Sharpnosed leafhopper
Scaphytopius magdalensis

Symptoms
There are very few outward symptoms of feeding by this insect but they are considered a major pest as they transmit a mycoplasma-like organism that causes blueverry stunt; the adult insect is small and brown reaching approximately 5 mm in length with small cream colored patches on the body and wings; both adult and nymphal stages have a pointed head
Cause
Insect
Comments
In Southern regions, the sharpnosed leafhopper may undergo three generations per year; adult insects are capable of flying long distances and will also feed on huckleberry
Management
Plantations of blueberry can be monitored for sharpnose leafhoppers through the use of yellow sticky traps; insecticides registered for use on blueberry are generally quite effective at reducing leafhopper populations and should be applied to coincide with leafhopper dispersal to limit the spread of blueberry stunt

Flea beetle (Blueberry flea beetle)
Altica sylvia

Symptoms
Small holes or pits in leaves that give the foliage a characteristic “shothole” appearance; young plants and seedlings are particularly susceptible; plant growth may be reduced; if damage is severe the plant may be killed; the pest responsible for the damage is a small (1.5–3.0 mm) dark colored beetle which jumps when disturbed; the beetles are often shiny in appearance
Cause
Insect
Comments
Younger plants are more susceptible to flea beetle damage than older ones; older plants can tolerate infestation; flea beetles may overwinter on nearby weed species, in plant debris or in the soil; insects may go through a second or third generation in one year
Management
In areas where flea beetles are a problem, floating row covers may have to be used prior to the emergence of the beetles to provide a physical barrier to protect young plants; plant seeds early to allow establishment before the beetles become a problem - mature plants are less susceptible to damage; trap crops may provide a measure of control - cruciferous plants are best; application of a thick layer of mulch may help prevent beetles reaching surface; application on diamotecoeus earth or oils such as neem oil are effective control methods for organic growers; application of insecticides containing carbaryl, spinosad, bifenthrin and permethrin can provide adequate control of beetles for up to a week but will need reapplied

Japanese beetle
Popillia japonica

Symptoms
Leaves skeletonized (only veins remaining); flowers and buds damaged; plant damage may be extensive; adult insect is a metallic green-bronze beetle with tufts of white hair protruding from under wing covers on each side of the body; adult beetles are approximately 13 mm in length; larvae are cream-white grubs which develop in the soil
Cause
Insect
Comments
One beetle generation every 1-2 years; pheromone traps may actually attract more beetles to home gardens and should generally be avoided; beetle overwinters as larvae in soil; beetle has an extensive range of over 300 host plants
Management
If beetles were a problem in the previous year, use floating row covers to protect plants or spray kaolin clay; adult beetles can be hand picked from plants and destroyed by placing in soapy water; parasitic nematodes can be applied to soil to reduce the number of overwintering grubs; insecticidal soaps or neem oil can help reduce beetle populations

Thrips (Various spp)
e.g.Frankliniella vaccinii
Frankliniella tritici
etc.

Symptoms
Leaves curling around the stem beginning at stem tip; as new leaves emerge, the curling spreads from tip to base of stem; If population is high leaves may be distorted; flowers may be damaged; insect is small (1.5 mm) and slender and best viewed using a hand lens; adult thrips are pale yellow to light brown and the nymphs are smaller and lighter in color
Cause
Insect
Comments
Larvae pupate in soil; the time between egg and adult insect is approximately 3 weeks depending on ambient temperature
Management
Infested areas can be removed by pruning; in commercial plantations the insecticides registered can be very toxic to bees and should be applied at dusk when bees are not actively flying

Phytophthora root rot
Phytophthora cinnamoni

Symptoms
Yellowing leaves; lack of new growth on plants; highbush varieties become stunted and turn red; rabbit eye varieties may become chlorotic and srop leaves
Cause
Oomycete
Comments
Disease emergence is favored by water-logged soils and warm temperatures; disease is spread by movement of contaminated water and soil
Management
The best method of controlling phytophthora root rot is through the use of good cultural practices: plant blueberries in well-draining soils or in raised beds; sanitize all tool sand equipment regularly; avoid transferring soil between sites

Shoestring
Blueberry shoestring virus (BBSSV)

Symptoms
Elongated reddish streaks on green stems; purplish red leaves; cupped leaves; leaves may be elongated or strap-like; reddish-purple fruit
Cause
Virus
Comments
Infected plants do not show symptoms of disease for 4 years or more. During this latent period the virus can be spread to other plants making the removal of visibly infected bushes an ineffective control method; virus is transmitted by aphids
Management
One of the most effective methods of preventing the spread of the virus is to time applications of insecticides to coincide with aphid emergence; the first application is usually made in late May or early June; any equipment used to apply insecticides should be cleaned thoroughly before moving to a new area