On behalf of the Vaccinium Species Working Group, Vine and Berry Fruits Section of the International Society for Horticultural Science (ISHS), the conveners and organizing committee invite you to attend the10th International Vaccinium Symposium, to be held June 17-22, 2012 in Maastricht, Province of Limburg, The Netherlands. The meeting is being held in conjunction with the Floriade 2012 World Horticultural Expo: http://www.floriade.nl/
For more information or to contact the conveners, please visit the symposium website: http://www.vaccinium2012.com/
I look forward to seeing you in Maastricht!
Bill Cline, Chair
ISHS Vaccinium Working Group
Wednesday, November 30, 2011
2012 Blueberry Open House and Trade Show
The 46th Annual Open House of the North Carolina Blueberry Council is coming up on January 10th and 11th, 2012. The meeting will be held at the Sampson Agri-Exposition Center in Clinton, NC at 414 Warsaw Road near the intersection of Hwy 24 and Hwy 701 business. For more information or to preregister, Contact Julie Woodcock at (910) 471-3193, or email ncblueberry@bellsouth.net
Thursday, October 6, 2011
Evaluating leafspot effects
Late September is a good time of year to evaluate the effects of leaf spot diseases. If most of your leaves are still attached to the bush at this time of year, then most likely flower bud formation has occurred and the crop potential for next year is good. If, however, your leaves have already detached by the end of September, then chances are that some flower buds did not form due to premature defoliation, and crop potential for next year has already been reduced.
The image below shows three twigs from the cultivar Star, collected on 30 Sep 2011. Star is susceptible to Septoria leaf spot caused by the fungus Septoria albopunctata. These are older twigs from the first flush of leafy growth in spring, and by now should have formed visible flower buds at the base of each leaf.
The shoot on the left is from a bush that was protected with a fungicide, retained its leaves, and has formed 5-6 flower buds. The unprotected shoot in the middle defoliated early, and by comparison formed only a couple of flower buds at the tip. The shoot on the far right was also defoliated early, not by leaf spots but by hurricane Irene. It too, has only one or two flower buds. Note that the shoot defoliated by hurricane winds still has the leaf petioles (bases) attached -- the leaves did not abscise normally, but were torn away: This also happens (leaves missing, but petioles still attached) with caterpillar feeding damage.
Regardless of the cause, when the leaves are taken away too early, flower buds do not form, and the potential crop is reduced for the following year -- because fewer flower buds means fewer berries.
The two main fungal leaf spot diseases that cause defoliation on blueberries in North Carolina are Septoria leaf spot caused by Septoria albopunctata, and Anthracnose leaf spot, caused by Gloeosporium minus. The two diseases have very different symptoms, as shown below:
Anthracnose leaf spot, shown above, consists of large lesions that often occur at the edge of the leaf. Examples of susceptible cultivars are Pender (shown) and Duke.
Septoria leaf spot, by comparison, produces dozens of small lesions on each leaf. The southern highbush cultivar Star (shown) is very susceptible.
By evaluating leaf drop at this time each year, growers can get a good idea of how much disease pressure they have on their farm, whether fungicide use is warranted, and which cultivars are susceptible.
The image below shows three twigs from the cultivar Star, collected on 30 Sep 2011. Star is susceptible to Septoria leaf spot caused by the fungus Septoria albopunctata. These are older twigs from the first flush of leafy growth in spring, and by now should have formed visible flower buds at the base of each leaf.
The shoot on the left is from a bush that was protected with a fungicide, retained its leaves, and has formed 5-6 flower buds. The unprotected shoot in the middle defoliated early, and by comparison formed only a couple of flower buds at the tip. The shoot on the far right was also defoliated early, not by leaf spots but by hurricane Irene. It too, has only one or two flower buds. Note that the shoot defoliated by hurricane winds still has the leaf petioles (bases) attached -- the leaves did not abscise normally, but were torn away: This also happens (leaves missing, but petioles still attached) with caterpillar feeding damage.
Regardless of the cause, when the leaves are taken away too early, flower buds do not form, and the potential crop is reduced for the following year -- because fewer flower buds means fewer berries.
The two main fungal leaf spot diseases that cause defoliation on blueberries in North Carolina are Septoria leaf spot caused by Septoria albopunctata, and Anthracnose leaf spot, caused by Gloeosporium minus. The two diseases have very different symptoms, as shown below:
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| Anthracnose leaf spot (Gloeosporium minus) |
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| Septoria leaf spot (Septoria albopunctata) |
By evaluating leaf drop at this time each year, growers can get a good idea of how much disease pressure they have on their farm, whether fungicide use is warranted, and which cultivars are susceptible.
Tuesday, September 27, 2011
Cylindrocladium blight
Cylindrocladium blight is a disease caused by a plant pathogenic fungus. Infection results in leaf spots, brown, dead stems, and often dead plants. On blueberry it is a disease of propagation and nursery beds, and is rarely seen on plants in the field. Symptoms commonly appear in blueberry rooting beds in the late summer and into fall. The disease may also occur in potted plants that are spaced too close together in pot yards. One species of this particular fungus also infects peanut plants in the field, so blueberry propagators in North Carolina often call the disease "peanut blight". There are many species of Cylindrocladium that infect plants, and there may be more than one species of this fungus causing disease in blueberry rooting beds. At present the only species reported on blueberry in North Carolina is now considered to be Cylindrocladium parasiticum, hence the common name of the disease, Cylindrocladium blight.
The disease is most often seen in propagation beds and pot yards that have grown vigorously and are too dense to allow proper air movement between plants. Spores of the fungus infect leaves and stems, and eventually kill entire plants. Often the root system is the last healthy part remaining. The phenomenon of plants dying in the center of a dense block, while those at the edge (with better air circulation) survive, is characteristic of this disease in dense beds of plants.
In pot yards and late-stage propagation beds where the plants have already formed roots, this disease is best managed by not over-watering or over-fertilizing plants, and by maintaining proper plant spacing so that the leaves and stems can dry between waterings. Cull to remove and discard any dead plants, and space the remaining plants out as much as possible so that there is good air movement between the bushes. Do not re-use any old used potting media, as this disease can carry over from one year to the next in contaminated soil or potting mix. Clean up as much debris as possible and sanitize the bed area and any pots that you plan to re-use.
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| Cylindrocladium blight in a bed of softwood cuttings in late fall. |
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| Closeup of orange fungal fruiting bodies on an infected cutting |
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| Irregular-shaped spots on lower leaves of older rooted cuttings |
The disease is most often seen in propagation beds and pot yards that have grown vigorously and are too dense to allow proper air movement between plants. Spores of the fungus infect leaves and stems, and eventually kill entire plants. Often the root system is the last healthy part remaining. The phenomenon of plants dying in the center of a dense block, while those at the edge (with better air circulation) survive, is characteristic of this disease in dense beds of plants.
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| Large area of dead plants in a propagation bed late in the season |
In pot yards and late-stage propagation beds where the plants have already formed roots, this disease is best managed by not over-watering or over-fertilizing plants, and by maintaining proper plant spacing so that the leaves and stems can dry between waterings. Cull to remove and discard any dead plants, and space the remaining plants out as much as possible so that there is good air movement between the bushes. Do not re-use any old used potting media, as this disease can carry over from one year to the next in contaminated soil or potting mix. Clean up as much debris as possible and sanitize the bed area and any pots that you plan to re-use.
Tuesday, August 23, 2011
Blueberry Stem Canker
Blueberry stem canker caused by the fungus Botryosphaeria corticis is common on cultivated and wild blueberries in North Carolina. The disease spreads by spores and through the use of infected cutting wood for propagation. Canker is important because it can weaken and kill susceptible or stressed bushes.
Symptoms: Cankers are noticeably thicker than adjacent portions of the stem, forming raised areas with deep cracks. Usually only short sections of the stem are affected, though canes of some very susceptible cultivars can have multiple infection points along their entire length.
Disease cycle: Infection of stems is by spores (ascospores and conidia) that are released during wet weather and disseminated by wind from April through September. Young, succulent, actively growing shoots are infected, and symptoms appear within 4 to 6 months after infection. As the fungus continues to grow and invade the wood, large cankers with deep fissures and cracks develop that girdle, weaken and kill the stem.
Control: Fungicides are partially effective but not practical. Control relies on maintaining general plant health,
pruning to remove canker-weakened canes,use of resistant cultivars, and use of disease-free planting stock. Cutting wood should be selected from undiseased plants, or the plants sourced from disease-free nurseries. In areas where canker is not present, the use of disease-free planting stock is critical to avoid introducing this pathogen to an new field.
Highbush blueberry: Among the popular southern highbush cultivars (Vaccinium corymbosum) grown in eastern NC, O'Neal, Blueridge and Legacy are susceptible -- however all three are successfully grown where plant health is maintained via proper site selection, fertility, pruning and irrigation.
Rabbiteye blueberry: Cankers can be numerous on rabbiteye blueberries (Vaccinium virgatum, synonym V. ashei) but generally do not cause yield loss on this vigorous blueberry species.
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| 'O'Neal' canes dying out due to canker infections |
Symptoms: Cankers are noticeably thicker than adjacent portions of the stem, forming raised areas with deep cracks. Usually only short sections of the stem are affected, though canes of some very susceptible cultivars can have multiple infection points along their entire length.
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| Swollen area (at center) with deep cracks is a fully developed canker |
Disease cycle: Infection of stems is by spores (ascospores and conidia) that are released during wet weather and disseminated by wind from April through September. Young, succulent, actively growing shoots are infected, and symptoms appear within 4 to 6 months after infection. As the fungus continues to grow and invade the wood, large cankers with deep fissures and cracks develop that girdle, weaken and kill the stem.
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| Cankers on a young stem, exuding spores |
Control: Fungicides are partially effective but not practical. Control relies on maintaining general plant health,
pruning to remove canker-weakened canes,use of resistant cultivars, and use of disease-free planting stock. Cutting wood should be selected from undiseased plants, or the plants sourced from disease-free nurseries. In areas where canker is not present, the use of disease-free planting stock is critical to avoid introducing this pathogen to an new field.
Highbush blueberry: Among the popular southern highbush cultivars (Vaccinium corymbosum) grown in eastern NC, O'Neal, Blueridge and Legacy are susceptible -- however all three are successfully grown where plant health is maintained via proper site selection, fertility, pruning and irrigation.
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| Cankers on a one-year-old 'Legacy' stem |
Rabbiteye blueberry: Cankers can be numerous on rabbiteye blueberries (Vaccinium virgatum, synonym V. ashei) but generally do not cause yield loss on this vigorous blueberry species.
Monday, August 22, 2011
Collecting softwood cuttings
As discussed in a previous post, blueberries can be easily propagated in summer from leafy softwood cuttings by using an intermittent mist system to keep the cuttings from drying out during the six- to eight-week rooting period. However, a specific stage of shoot growth must be selected for cuttings, because not all leafy shoots will root -- those that are too old will tend to form flower buds rather than roots, and cuttings from shoots that are too young and succulent will wilt before rooting can occur. The photos below illustrate when and how to collect and stick softwood cuttings.
Timing: Collect cuttings when shoots are 10-12 inches long and semi-hardened. In southeastern NC, this occurs in late May and again in late July or early August:
Age of cuttings: Select cuttings with leaves that are intermediate in color between the darkest older leaves and the palest young shoots. Softwood cuttings should be immature but not succulent. Cuttings that snap easily when bent are too young -- the cuttings should be bendable and becoming woody.
Handling: Collect cuttings early in the morning if possible, to minimize wilting. Once collected, cuttings are susceptible to wilting and must be kept moist and cool. Sprinkle with water and store in a cooler with ice until ready to stick the cuttings in the rooting bed. Caution -- direct contact with too much ice can damage cuttings -- keep them cool but not icy.
Sticking cuttings: Cuttings are stuck into six- to eight-inch deep rooting beds filled with aged milled pine bark. Stick the cuttings 1.5 to 2 inches apart in rows by cultivar. Approximately half the length of the cutting should be in the bark, with only the leafy section above the bark. The mist system should be running during this process so that the cuttings are never allowed to dry out.
Cuttings typically root within six to eight weeks. Once fully dormant, the cuttings can be dug and either potted, or planted directly into the field. Most nurseries and commercial growers pot rooted cuttings and grow them out for a year prior to selling or setting in the field.
For further reading:
Krewer, G. K. and W. O.Cline. 2003. Blueberry Propagation Suggestions.
Bilderback, T. E., R. E. Bir and M. A. Powell 1993. A Simple Intermittent Mist System for Propagation.
Timing: Collect cuttings when shoots are 10-12 inches long and semi-hardened. In southeastern NC, this occurs in late May and again in late July or early August:
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| Blueberry bush in early August with suitable shoots for propagation |
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| Cuttings can be snapped off by hand or clipped with pruning shears |
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| Pinch off the top of the cutting and remove the lower leaves |
Age of cuttings: Select cuttings with leaves that are intermediate in color between the darkest older leaves and the palest young shoots. Softwood cuttings should be immature but not succulent. Cuttings that snap easily when bent are too young -- the cuttings should be bendable and becoming woody.
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| Leafy shoots from oldest to youngest. The two in the center are suitable for propagation. |
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| Softwood cuttings of the proper stage are bendable but do not snap |
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| Shoots that snap easily when bent are too succulent for outdoor propagation beds |
Handling: Collect cuttings early in the morning if possible, to minimize wilting. Once collected, cuttings are susceptible to wilting and must be kept moist and cool. Sprinkle with water and store in a cooler with ice until ready to stick the cuttings in the rooting bed. Caution -- direct contact with too much ice can damage cuttings -- keep them cool but not icy.
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| Take a cooler and water to the field to keep cuttings from wilting |
Sticking cuttings: Cuttings are stuck into six- to eight-inch deep rooting beds filled with aged milled pine bark. Stick the cuttings 1.5 to 2 inches apart in rows by cultivar. Approximately half the length of the cutting should be in the bark, with only the leafy section above the bark. The mist system should be running during this process so that the cuttings are never allowed to dry out.
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| A measuring stick is used to space the cuttings evenly across the bed. |
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| Cuttings are stuck approximately half their lengh in the bark |
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| A commercial rooting bed partially filled with cuttings |
Cuttings typically root within six to eight weeks. Once fully dormant, the cuttings can be dug and either potted, or planted directly into the field. Most nurseries and commercial growers pot rooted cuttings and grow them out for a year prior to selling or setting in the field.
For further reading:
Krewer, G. K. and W. O.Cline. 2003. Blueberry Propagation Suggestions.
Bilderback, T. E., R. E. Bir and M. A. Powell 1993. A Simple Intermittent Mist System for Propagation.
Wednesday, August 3, 2011
Blueberry cultivar 'LEGACY'
Released: 1993 (not patented)
Developed by: USDA and NJAES, Rutgers University
Selection number: G-290
Parentage: 'Elizabeth' x US75 (Vaccinium darrowi,'Florida 4B', x 'Bluecrop')
Species/Type: Vaccinium corymbosum (southern highbush)
Bloom date: April 1 in southeastern NC (approx 1 wk before 'Croatan')
Harvest season: First harvest around May 30 - June 3 in southeastern NC
Chill requirement: Estimated to be 700 to 800 hours below 45F
Description: Upright, open habit with flexible canes. Highly vigorous, forming an abundance of flower buds on both longer canes and lateral fruiting twigs. Often a few leaves from the previous season will overwinter, persisting until after bloom the following spring. Early-blooming with pure white,elongate flowers. Fruit light blue, firm, with excellent flavor; large berries becoming medium in size with successive harvests, small dry stem scar. Clusters are open and well suited to mechanical harvest. Berries maintain their quality even when slightly overripe, and are less prone to decay than other highbush cultivars.
Good Characteristics: Blooms exhibit cold hardiness during spring freezes. 'Legacy' is highly productive with high-quality fruit that can be hand- or machine-harvested for the fresh market. Widely adapted to different soil types, 'Legacy' is a good candidate for highbush production on pine-bark-amended soils in the piedmont.
Flaws: Early blooming may result in yield loss due to spring freezes. 'Legacy' ripens two to three weeks later than early cultivars like 'Star' and 'O'Neal'. 'Legacy' is susceptible to blueberry stem canker disease caused by the fungus Botryosphaeria corticis, and will require irrigation and selective pruning to manage this disease. Purchase of disease-free propagation stock will reduce or delay the effects of stem canker.
Potential: Rapidly becoming a leading cultivar in North Carolina due to high yields and excellent fruit quality, 'Legacy' is recommended for commercial planting on lowland blueberry soils in southeastern NC, and for trial plantings in amended upland soils in the coastal plain and piedmont.
Developed by: USDA and NJAES, Rutgers University
Selection number: G-290
Parentage: 'Elizabeth' x US75 (Vaccinium darrowi,'Florida 4B', x 'Bluecrop')
Species/Type: Vaccinium corymbosum (southern highbush)
Bloom date: April 1 in southeastern NC (approx 1 wk before 'Croatan')
Harvest season: First harvest around May 30 - June 3 in southeastern NC
Chill requirement: Estimated to be 700 to 800 hours below 45F
Description: Upright, open habit with flexible canes. Highly vigorous, forming an abundance of flower buds on both longer canes and lateral fruiting twigs. Often a few leaves from the previous season will overwinter, persisting until after bloom the following spring. Early-blooming with pure white,elongate flowers. Fruit light blue, firm, with excellent flavor; large berries becoming medium in size with successive harvests, small dry stem scar. Clusters are open and well suited to mechanical harvest. Berries maintain their quality even when slightly overripe, and are less prone to decay than other highbush cultivars.
Good Characteristics: Blooms exhibit cold hardiness during spring freezes. 'Legacy' is highly productive with high-quality fruit that can be hand- or machine-harvested for the fresh market. Widely adapted to different soil types, 'Legacy' is a good candidate for highbush production on pine-bark-amended soils in the piedmont.
Flaws: Early blooming may result in yield loss due to spring freezes. 'Legacy' ripens two to three weeks later than early cultivars like 'Star' and 'O'Neal'. 'Legacy' is susceptible to blueberry stem canker disease caused by the fungus Botryosphaeria corticis, and will require irrigation and selective pruning to manage this disease. Purchase of disease-free propagation stock will reduce or delay the effects of stem canker.
Potential: Rapidly becoming a leading cultivar in North Carolina due to high yields and excellent fruit quality, 'Legacy' is recommended for commercial planting on lowland blueberry soils in southeastern NC, and for trial plantings in amended upland soils in the coastal plain and piedmont.
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