The following are some azalea cultivars that are resistant to lace bug.
Lace bugs are a frequent pest on azalea, rhododendron, pyracantha and other hosts. These laceywinged insects feed on the undersides of leaves, suck leaf sap and leave a chlorotic dot on the upper leaf surface. They overwinter as eggs inserted into the leaves. Black varnish spots on the underside of leaves is diagnostic for this insect. Management techniques may involve malathion, insecticidal soap, pyrethroids, and resistant varieties.
The following azalea cultivars have resistance to azalea lace bug:
Dawn
Pink Star
Ereka
Cavalier
Pink Fancy
Dram
Seigei
Macrantha
Salmon Pink
Elsie Lee
Red Wing
Sunglow
Marilee
Information from the 2007 Nursery Crops Short Course, Mountain Horticultural Crops Research and Extension Center, Fletcher, NC, North Carolina State University.
Showing posts with label azalea. Show all posts
Showing posts with label azalea. Show all posts
Friday, October 23, 2009
Saturday, September 26, 2009
Landscape - Azalea Lace Bug
The last generation of Azalea lace bug is now active in Delaware. The following is more information.
Last Generation of Azalea Lace Bug Active
Azalea lace bug (Stephanitis pyriodes), nymphs and some adults are present in Delaware. The adults will be laying eggs in October and the insects overwinter in the egg stage. The eggs are inserted into foliage, usually along the midvein area. We usually see nymphs in May in Delaware and can see at least 2 to 3 generations per year. In southern Delaware where the growing season is a little longer the 3rd generation is more likely. Azalea lace bug populations tend to be highest when plants are grown in full sun and the damage can be the most severe at these sites.
Cultural control: The best thing you can advise your clientele to do is to stop growing rhododendrons and azaleas in full sun and move them into areas of filtered shade or landscapes with shade part of the day. Also, keep pH low with acidic mulch (pine needles, pine bark) and soil moisture even. A stressed plant is more likely to show heavier injury.
Chemical Control: Imidacloprid has been used by most landscape managers for the last decade. Some are starting to use some of the newer neonicotinoids such as Flagship and Safari for lace bug control. The imidacloprid has controlled both species of lace bug for at least a full growing season. We have had several landscape mangers report that they continue to see control carry into a second season.
Photo of azalea lace bug damage by Whitney Cranshaw, Colorado State University, Bugwood.org
Adapted for Delaware from an article in the September 25, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/09Sep25L.pdf
Last Generation of Azalea Lace Bug Active
Azalea lace bug (Stephanitis pyriodes), nymphs and some adults are present in Delaware. The adults will be laying eggs in October and the insects overwinter in the egg stage. The eggs are inserted into foliage, usually along the midvein area. We usually see nymphs in May in Delaware and can see at least 2 to 3 generations per year. In southern Delaware where the growing season is a little longer the 3rd generation is more likely. Azalea lace bug populations tend to be highest when plants are grown in full sun and the damage can be the most severe at these sites.
Cultural control: The best thing you can advise your clientele to do is to stop growing rhododendrons and azaleas in full sun and move them into areas of filtered shade or landscapes with shade part of the day. Also, keep pH low with acidic mulch (pine needles, pine bark) and soil moisture even. A stressed plant is more likely to show heavier injury.
Chemical Control: Imidacloprid has been used by most landscape managers for the last decade. Some are starting to use some of the newer neonicotinoids such as Flagship and Safari for lace bug control. The imidacloprid has controlled both species of lace bug for at least a full growing season. We have had several landscape mangers report that they continue to see control carry into a second season.
Adapted for Delaware from an article in the September 25, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/09Sep25L.pdf
Friday, April 3, 2009
Landscape - Scale Insects: Azalea Bark Scale
This is the first in a series on scale insects in the landscape. It is a description of the Azalea bark scale. Information is from the University of Maryland.
Azalea Bark Scale (Acanthococcus azaleae), Family Erioccicdae
Plants Damaged: This scale is a pest of azaleas and rhododendrons. This scale has been reported on hawthorn, Andromeda, poplar, willow and ornamental cherry trees.
Damage Symptoms: Azalea bark scale has become recognized as a prominent pest of azaleas. Infested plants usually appear chlorotic and unthrifty. Infested plants are often covered with sooty mold, a black fungus that grows on the honeydew excreted by the azalea bark scales as they feed. Eventually twigs may die back.
Life Cycle: As the female azalea bark scale matures, it secretes white, waxy threads, which become felted or matted into a thick covering over its entire body. Females lay eggs in this white wax. As the female lays eggs, its body shrivels gradually as the egg sac fills with eggs. Eggs are laid in May. They hatch in central Maryland in late May to early June. Individual crawlers are active and moving for 12 – 24 hours. New crawlers continue to emerge over a couple of weeks. There are two generations in Maryland. This new generation matures during the summer and produces eggs in September. Mature females tend to feed in crotches and on twigs. Adult males, two-winged and tiny, tend to feed on the leaves. Azalea bark scale overwinters as immatures in the forks of the twigs.
Control: If the population is low and damage is minimal, look for beneficial insects which do a good job controlling this insect. If necessary, apply a dormant spray for overwintering nymphs on twigs. In summer when crawlers are active, you can use a summer rate (0.5 – 1.0%) of horticultural oil for control.
Azalea bark scale. Photo from the United States National Collection of Scale Insects Photographs Archive, USDA Agricultural Research Service, Bugwood.org
Azalea bark scale crawler activity.
Information from "Scales Commonly Encountered in Maryland Landscapes and Nurseries" by Stanton Gill, Extension Specialist in IPM for Nurseries and Greenhouses,and Suzanne Klick and Shannon Wadkins, Technicians, Central Maryland Research and Education Center University of Maryland Cooperative Extension.
Azalea Bark Scale (Acanthococcus azaleae), Family Erioccicdae
Plants Damaged: This scale is a pest of azaleas and rhododendrons. This scale has been reported on hawthorn, Andromeda, poplar, willow and ornamental cherry trees.
Damage Symptoms: Azalea bark scale has become recognized as a prominent pest of azaleas. Infested plants usually appear chlorotic and unthrifty. Infested plants are often covered with sooty mold, a black fungus that grows on the honeydew excreted by the azalea bark scales as they feed. Eventually twigs may die back.
Life Cycle: As the female azalea bark scale matures, it secretes white, waxy threads, which become felted or matted into a thick covering over its entire body. Females lay eggs in this white wax. As the female lays eggs, its body shrivels gradually as the egg sac fills with eggs. Eggs are laid in May. They hatch in central Maryland in late May to early June. Individual crawlers are active and moving for 12 – 24 hours. New crawlers continue to emerge over a couple of weeks. There are two generations in Maryland. This new generation matures during the summer and produces eggs in September. Mature females tend to feed in crotches and on twigs. Adult males, two-winged and tiny, tend to feed on the leaves. Azalea bark scale overwinters as immatures in the forks of the twigs.
Control: If the population is low and damage is minimal, look for beneficial insects which do a good job controlling this insect. If necessary, apply a dormant spray for overwintering nymphs on twigs. In summer when crawlers are active, you can use a summer rate (0.5 – 1.0%) of horticultural oil for control.
Information from "Scales Commonly Encountered in Maryland Landscapes and Nurseries" by Stanton Gill, Extension Specialist in IPM for Nurseries and Greenhouses,and Suzanne Klick and Shannon Wadkins, Technicians, Central Maryland Research and Education Center University of Maryland Cooperative Extension.
Thursday, May 22, 2008
Nursery and Landscape - Azalea Lace Bug
Azalea lace bug is the most common pest that attacks Azaleas in Delaware. The following is some information on this pest and its control.
AZALEA LACE BUG: Adults will become active by mid-late May, feeding and laying eggs on the underside of azalea foliage. Leaves appear stippled and offcolored. Look for black fecal spots on the underside of foliage or for the lacy winged adults. Spiny black nymphs will also be noticeable by the end of the month. Azaleas planted in full sun and under drought stress exhibit the worst damage. Control with acephate (Orthene) when active life stages are first seen. Note that while insecticidal soap has offered good (>85%) control, obtaining contact with lace bugs on the underside of foliage may prove daunting on small plants. Field studies have shown that Imidichloprid (Merit) will provide excellent control for at least a full calendar season. Hence, it may be unnecessary to apply Merit to the same plant every year.
Reprinted from the May 1, 2008 Edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition, Rutgers University.
AZALEA LACE BUG: Adults will become active by mid-late May, feeding and laying eggs on the underside of azalea foliage. Leaves appear stippled and offcolored. Look for black fecal spots on the underside of foliage or for the lacy winged adults. Spiny black nymphs will also be noticeable by the end of the month. Azaleas planted in full sun and under drought stress exhibit the worst damage. Control with acephate (Orthene) when active life stages are first seen. Note that while insecticidal soap has offered good (>85%) control, obtaining contact with lace bugs on the underside of foliage may prove daunting on small plants. Field studies have shown that Imidichloprid (Merit) will provide excellent control for at least a full calendar season. Hence, it may be unnecessary to apply Merit to the same plant every year.
Reprinted from the May 1, 2008 Edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition, Rutgers University.
Monday, April 7, 2008
Landscape and Nursery - Phytophthora Root Rot in Rhododendron and Azalea
Each year we commonly see many plants that succomb to Phytophthora root rot. Rhododendrons and Azaleas often are killed by this disease. The following is an article on the subject from Virginia Tech.
Wilt and root rot of rhododendron and azalea are symptoms of a disease caused by the soil-inhabiting water mold fungus Phytophthora. Several different spe of Phytophthora have been reported to cause similar symptoms, but Phytophthora cinnamomi and Phytophthora parasitica are recovered most frequently from diseased plants in Virginia. In addition to rhododendron and azalea, Phytophthora species also frequently infect many cultivars of boxwood, andromeda, mountain laurel, blueberry, camellia, juniper, and yew.
In the early stages of disease, symptoms consist of retarded growth, slight drooping of the foliage and off-color foliage. Infected broadleaf species wilt during the heat of the day and recover at night. Roots become discolored and die. Dark or reddish brown discoloration may extend up into the wood of the lower stem. Severely affected plants wilt permanently and turn brown.
Environmental Factors Favoring Disease
Disease development is favored by high soil moisture and soil temperatures of 80°F and above. Infected plants growing on sandy soils are generally not as seriously affected by the disease, whereas those growing on poorly drained soils wilt and die. On well-drained soils, only feeder rootlets are rotted, but when drainage is poor, the main roots and stem become discolored and infected plants wilt and die. Many areas of Delaware have soil that is heavy in clay, poorly drained, and conducive to Phytophthora root rot. Infected plants may also be brought into Delaware from other states. These plants may appear healthy when received, but wilt from root rot when exposed to local conditions of high soil moisture and high temperatures. Plants with root systems impaired by Phytophthora root rot may also be more sensitive to subsequent periods of drought.
Losses from Phytophthora root rot in commercial operations have decreased due to the increased use of well draining mixes, such as 100% pine bark. In general, root rot occurs less frequently on plants grown in mixtures that have an air volume of 20-25%.
Control
Landscape
Planting sites should be well-drained. Growers often misinterpret wilt as a sign that a plant needs water and respond by applying more water. This reaction should be avoided in sites where plants are clearly receiving adequate water. The use of drain tiles to prevent rain water from collecting on the surface is suggested. Special care should be taken to set plants high so that the soil line is not more than one inch above the upper roots. Where subsoils are known to be poorly drained, planting on raised beds should be considered. After planting, the soil should not be mounded up around the base of the stem because this increases susceptibility to disease.
Chemical Control
Chemical control of Phytophthora root rot in established plantings of rhododendrons and azaleas is difficult. However, the spread of the fungus from diseased plants to adjacent healthy plants may be checked by drenching soil around the healthy plants with a fungicide containing mefenoxam (e.g. Subdue MAXX), metalaxyl (e.g. Subdue), fosetyl-Al (e.g. Aliette), etridiazole (e.g. Truban) or etridiazole + thiophanate methyl (e.g. Banrot). Follow label rates and treat at four-week intervals during the summer when environmental conditions are favorable for disease.
In locations where plants have died from Phytophthora root rot in the home landscape, it would be advisable to replant with a cultivar that has resistance to the disease. Lists of cultivars of azalea and rhododendron that are reported to have moderate to excellent resistance to Phytophthora root rot are available.
Propagation
Before sticking a new crop of cuttings, remove old rooting media from the propagating benches. To reduce the possibility of pathogen infestations originating from soil on the floor of the greenhouse, propagate on raised benches. Flats, baskets, and greenhouse benches can be treated with a disinfectant, such as Greenshield or Physan 2.0, to eradicate plant pathogens from surfaces. Propagating tools should be steam-sterilized or soaked in a commercial disinfectant. If a commercial disinfectant is not available, use household bleach containing sodium hypochlorite (1 part bleach to 9 parts water). Propagating benches should also be surface-sterilized between each set of cuttings prior to filling with sterile rooting media.
Containers
Containers should be placed on well drained sites, preferably on rock or gravel, so that any surface water contaminated with Phytophthora zoospores, which are motile in water, cannot enter the container through the bottom. Growing areas can be crowned to facilitate rapid runoff of water. If the water used for irrigation of containers is recycled, the hazard exists that the water may become contaminated with zoospores of Phytophthora spp. Chlorination will eliminate pathogens from the water.
Field
Some growers have learned to reduce disease losses in heavy soils naturally infested with Phytophthora species by growing plants on hills in rows or on well drained, raised beds. It is suspected that most of the field spread of Phytophthora spp. results from movement of fungal zoospores in water. Because it is possible to introduce Phytophthora spp. into fields through an irrigation system that draws and recirculates water from a catch basin or irrigation pond, chlorination of the water may be necessary to eradicate fungi.
Resistance
Many different rhododendron hybrids develop symptoms of Phytophthora root rot under natural conditions in Delaware. Field experiments with artificially inoculated plants have shown many well known hybrids and cultivars to be susceptible to P. cinnamomi, the most common species of Phytophthora found on azaleas and rhododendrons. However, some species and hybrids that have resistance to P. cinnamomi have been identified in experimental trials. Although performance of these species and hybrids in a given site may vary, resistant plants have a better chance of survival where Phytophthora diseases have been a problem in the past. Be sure to check with your nursery personnel for resistant cultivars.
Adapted from the factsheet "Phytophthora Root Rot of Rhododendron and Azalea" by Mary Ann Hansen, Extension Plant Pathologist, Department of Plant Pathology, Physiology and Weed Science, Virginia Tech. Go to the following site for the full article with resistant cultivar information go to http://www.ext.vt.edu/pubs/plantdiseasefs/450-615/450-615.html
Wilt and root rot of rhododendron and azalea are symptoms of a disease caused by the soil-inhabiting water mold fungus Phytophthora. Several different spe of Phytophthora have been reported to cause similar symptoms, but Phytophthora cinnamomi and Phytophthora parasitica are recovered most frequently from diseased plants in Virginia. In addition to rhododendron and azalea, Phytophthora species also frequently infect many cultivars of boxwood, andromeda, mountain laurel, blueberry, camellia, juniper, and yew.
In the early stages of disease, symptoms consist of retarded growth, slight drooping of the foliage and off-color foliage. Infected broadleaf species wilt during the heat of the day and recover at night. Roots become discolored and die. Dark or reddish brown discoloration may extend up into the wood of the lower stem. Severely affected plants wilt permanently and turn brown.
Environmental Factors Favoring Disease
Disease development is favored by high soil moisture and soil temperatures of 80°F and above. Infected plants growing on sandy soils are generally not as seriously affected by the disease, whereas those growing on poorly drained soils wilt and die. On well-drained soils, only feeder rootlets are rotted, but when drainage is poor, the main roots and stem become discolored and infected plants wilt and die. Many areas of Delaware have soil that is heavy in clay, poorly drained, and conducive to Phytophthora root rot. Infected plants may also be brought into Delaware from other states. These plants may appear healthy when received, but wilt from root rot when exposed to local conditions of high soil moisture and high temperatures. Plants with root systems impaired by Phytophthora root rot may also be more sensitive to subsequent periods of drought.
Losses from Phytophthora root rot in commercial operations have decreased due to the increased use of well draining mixes, such as 100% pine bark. In general, root rot occurs less frequently on plants grown in mixtures that have an air volume of 20-25%.
Control
Landscape
Planting sites should be well-drained. Growers often misinterpret wilt as a sign that a plant needs water and respond by applying more water. This reaction should be avoided in sites where plants are clearly receiving adequate water. The use of drain tiles to prevent rain water from collecting on the surface is suggested. Special care should be taken to set plants high so that the soil line is not more than one inch above the upper roots. Where subsoils are known to be poorly drained, planting on raised beds should be considered. After planting, the soil should not be mounded up around the base of the stem because this increases susceptibility to disease.
Chemical Control
Chemical control of Phytophthora root rot in established plantings of rhododendrons and azaleas is difficult. However, the spread of the fungus from diseased plants to adjacent healthy plants may be checked by drenching soil around the healthy plants with a fungicide containing mefenoxam (e.g. Subdue MAXX), metalaxyl (e.g. Subdue), fosetyl-Al (e.g. Aliette), etridiazole (e.g. Truban) or etridiazole + thiophanate methyl (e.g. Banrot). Follow label rates and treat at four-week intervals during the summer when environmental conditions are favorable for disease.
In locations where plants have died from Phytophthora root rot in the home landscape, it would be advisable to replant with a cultivar that has resistance to the disease. Lists of cultivars of azalea and rhododendron that are reported to have moderate to excellent resistance to Phytophthora root rot are available.
Propagation
Before sticking a new crop of cuttings, remove old rooting media from the propagating benches. To reduce the possibility of pathogen infestations originating from soil on the floor of the greenhouse, propagate on raised benches. Flats, baskets, and greenhouse benches can be treated with a disinfectant, such as Greenshield or Physan 2.0, to eradicate plant pathogens from surfaces. Propagating tools should be steam-sterilized or soaked in a commercial disinfectant. If a commercial disinfectant is not available, use household bleach containing sodium hypochlorite (1 part bleach to 9 parts water). Propagating benches should also be surface-sterilized between each set of cuttings prior to filling with sterile rooting media.
Containers
Containers should be placed on well drained sites, preferably on rock or gravel, so that any surface water contaminated with Phytophthora zoospores, which are motile in water, cannot enter the container through the bottom. Growing areas can be crowned to facilitate rapid runoff of water. If the water used for irrigation of containers is recycled, the hazard exists that the water may become contaminated with zoospores of Phytophthora spp. Chlorination will eliminate pathogens from the water.
Field
Some growers have learned to reduce disease losses in heavy soils naturally infested with Phytophthora species by growing plants on hills in rows or on well drained, raised beds. It is suspected that most of the field spread of Phytophthora spp. results from movement of fungal zoospores in water. Because it is possible to introduce Phytophthora spp. into fields through an irrigation system that draws and recirculates water from a catch basin or irrigation pond, chlorination of the water may be necessary to eradicate fungi.
Resistance
Many different rhododendron hybrids develop symptoms of Phytophthora root rot under natural conditions in Delaware. Field experiments with artificially inoculated plants have shown many well known hybrids and cultivars to be susceptible to P. cinnamomi, the most common species of Phytophthora found on azaleas and rhododendrons. However, some species and hybrids that have resistance to P. cinnamomi have been identified in experimental trials. Although performance of these species and hybrids in a given site may vary, resistant plants have a better chance of survival where Phytophthora diseases have been a problem in the past. Be sure to check with your nursery personnel for resistant cultivars.
Adapted from the factsheet "Phytophthora Root Rot of Rhododendron and Azalea" by Mary Ann Hansen, Extension Plant Pathologist, Department of Plant Pathology, Physiology and Weed Science, Virginia Tech. Go to the following site for the full article with resistant cultivar information go to http://www.ext.vt.edu/pubs/plantdiseasefs/450-615/450-615.html
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