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Commercial Horticulture May 16, 2014Coordinator Weekly IPM Report: Stanton Gill, Extension Specialist, IPM for Nursery, Greenhouse and Managed Landscapes, [email protected]. 301-596-9413 (office) or 410-868-9400 (cell)
Regular Contributors: Pest and Beneficial Insect Information: Stanton Gill and Paula Shrewsbury (Extension Specialists) Disease Information: Karen Rane (Plant Pathologist) and David Clement (Extension Specialist)Weed of the Week: Chuck Schuster (Extension Educator, Montgomery County)Cultural Information: Ginny Rosenkranz (Extension Educator, Wicomico/Worcester/Somerset Counties)Fertility Management: Andrew Ristvey (Regional Specialist, Wye Research & Education Center)Design, Layout and Editing: Suzanne Klick (Technician, CMREC)
In This Issue...
If you work for a commercial horticultural business in the area, you can report insect, disease, weed or cultural
plant problems found in the landscape or nursery to
TPM/IPM Weekly Report
Mowing TimeThe warm weather has really made the turfgrass grow and with it comes the mowing. We had a couple of emails reporting commercial lawn mowing equipment and homeowners driving their riding mowers and zero turn mowers on the sides of streets. Police have issued warnings and some tickets if the mowers do not have slow moving vehicle signs posted. Tell your workers and customers to make sure they use caution when moving between lawn areas and make sure they have the orange slow moving vehicle signs attached to the mowers.
- Mowing time- MDA container recycling- Request for scale insects- Caterpillars on euonymus- Winter damage reports- Boxwood psyllids- European pine sawfly- Emerald ash borer- Green tiger beetle- Scale updates- Fourlined plant bug- Ambrosia beetle update- Walnut twig beetle and thousand cankers disease- Imported willow leaf beetle- Lace bugs- Woolly aphids- Maple eyespot gall- Scab and rust- Oakleaf blister
Beneficial of the WeekWeed of the WeekPlant of the WeekPhenologyDegree DaysAnnouncements
IPMnet
Integrated Pest Management for
Commercial Horticulture
extension.umd.edu/ipm
Maryland Department of Agriculture Pesticide Container RecylingMDA has a brochure on the dates and details of the pesticide container recycling program which is available at: http://mda.maryland.gov/plants-pests/Documents/recycle.pdf
Request for Scale Insect SamplesWe are looking for samples of scale insects for a training program for master gardeners on May 29. If you find scale insects and can get them to us, we would appreciate it. You can reach us at 301-596-9413. Our address is 11975 Homewood Road, Ellicott City, MD 21042. Thank you.
Euonymus Leaf-notcher CaterpillarMarty Adams, Bartlett Tree Experts, reported euonymus leaf-notcher caterpillar (Pryeria sinica) feeding on Euonymus ‘Manhattan’ in Baltimore. This caterpillar, which is striped, is close to pupating at this point. Now is the time to start looking for the early stages of another euonymus caterpillar (Yponomeuta cagnagella), which is spotted.
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Winter DamageLast week we mentioned the winter damage on Leyland cypress and crape myrtles and asked for input on what you are seeing in your customer’s landscapes. We noted that in College Park, crape myrtles have dead tops, but suckers on lower part of plants. Some look better than others. Ginny Rosenkranz is not seeing any dieback on crape myrtles on the Eastern Shore. The following are the responses we received:
Valerie Pawlewicz, CPH, Your Personal GardenerI work in 40 private gardens in Annapolis, Crownsville and Severna Park. This spring I witnessed much damage or death on following plants: Damage to all Nandina domestica; death to all but one Loropetalum; damage to cherry laurels; damage to some Japanese hollies; death to all rosemary; damage to all lavenders and death to many of them. Lawn and Garden Company Reports from our customers include the following - Buddleia damaged and not resprouting or resprouting very irregularly, rosemary dead, figs dead or resprouting near ground, many of the Hydrangea macrophylla resprouting from ground level, Camellias showing severe winter damage, Kleim’s hardy gardenia dead, many azaleas showing winter damage and dying, many Buxus showing signs of damage and or dying and nandina severely damaged but resprouting. We are hearing these complaints from customers everyday.
Kyle Marsh, Homestead Gardens in DavidsonvilleWe have been getting countless numbers of people reporting damage to Ligustrum foliage, heavy dieback on hydrangeas, and fig trees that have died completely.
Beth ProppsI live on the MD/PA border in Frederick County. Our buddleia is cut back to roughly 10 inches above the ground every fall, and this spring we have mostly dead stems, with only a few very small leaves on a few stems starting to show. This is the first time it’s ever had any dead stems in the spring. We also had almost complete leaf drop on our honeysuckle, which has never happened before. However, they seem to be leafing out well.
Vincent Verweij, Arlington County Forester, Department of Parks and Natural ResourcesOne thing I’ve noticed, throughout the region, is the dieback of pretty much every fig tree I’ve seen. There is a need to protect these trees over the winter. The few I have seen doing ok were clearly netted and protected over the winter.
Matt Mitcheltree, North Hill Tree ExpertsSo far I have seen consistent damage and quite a few deaths in cherry laurels, hydrangeas, and butterfly bushes. There has also been a few dead and heavily damaged crape myrtles. American hollies, leyland cypress, and southern magnolias are showing damage as well as spotty damage in some taxus. All these are in and around the Baltimore area.
Bob & Wilma Muir, Deer Creek Valley Tree Farm, StreetJust writing, per your request in the latest IPM report, to say that we lost our nandina bushes and our butterfly bush due to the harsh winter. Crape myrtle is a late bloomer, so we’re still waiting to see if that survived!
Mary Revell, St. Michaels, Talbot County Master GardenerThis is what I see on my property: I was lucky: my nandinas and bayberries are ok, with no dieback, while I have seen dead ones or severely browned ones on other properties. My fig ‘Celeste’ is very slowly leafing out, but I think some branches may be dead. Some figs in my neighborhood appear to be dead to the roots, but sending out shoots from the roots. My camellia died. Liriope died down to the root but is now growing. Mondo grass may be dead in spots and was severely browned.
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Winter damage on viburnum and rhododendronPhotos: Karen Rane, UMD
More Winter InjuryFrom: Karen RaneWe continue to receive reports of winter damage on a number of woody ornamentals. Just a few weeks ago, this viburnum branch looked completely dead – the terminal bud was brown along with all of the foliage. However, this week new foliage has developed along the branch. Moral of the story – wait a bit before pruning out what looks like dead growth – there may still be some life in those “dead” branches!
Here’s another manifestation of winter injury – the flower buds on this rhododendron were damaged but not completely killed (one floret has developed from the brown central flower bud). The vegetative (leaf-producing) buds were not damaged, so they are elongating normally.
Connier Bowers, Garden Makeover CompanyHere are plants that notably had performed magnificently for many years, until this brutal winter.
1. Viburnum awabuki ‘Chindo’ (Chindo Sweet Viburnum), is an evergreen that has increased in popularity in recent years. It is not surprising how it fared this winter, as its northern zone limit is 7. Most are showing new tip growth, but they look very bad, in numerous locations from Silver Spring to Baltimore.
2. Brown Turkey Fig -- does not appear viable. Also not surprising as it is also just hardy to zone 7, but is one of the most commonly used figs around here. Many do not appear to have survived.
3. Crapemyrtle -- a dwarf Pocomoke does not appear viable. Some crapemyrtles are leafing out nicely. A ‘Sioux’ I just saw has some basal leaf growth, but nothing on the branches.
Viburnum awabuki ‘Chindo’Photo: Connie Bowers, Garden Makeover Company
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4. Camellia -- ‘Camellia ‘Arctic Dawn’ is a spring flowering Dr. Ackerman introduction and has flowered prolifically in recent years. The plants are alive (in different locations in northern Silver Spring), but the buds appear to have been killed off (winter burn or frost damage) and no flowering this spring.
5. Holly -- I have seen some yellowing leaves on Koehne and Nellie Stevens, but nothing dramatic.
6. Hydrangea -- Hydrangea macrophylla seems to have been subject to bud kill nearly universally around here. The plants all show basal leaf growth, but would not flower this year. Other hydrangeas (Oakleaf -- and Endless Summer are looking good).
Cameliia ‘Arctic Dawn’Photo: Connie Bowers, Garden Makeover Company
Boxwood PsyllidsSue Randall, Baltimore County Master Gardener, and Brian Scheck, Maxalea, are reporting activity of boxwood psyllids on boxwood in the Baltimore area. The damage (cupping of terminal leaves) by boxwood psyllid tends not to be aesthetically displeasing enough to warrant control measures in most cases. If you absolutely must control them, then you can apply a systemic insecticide as a foliar spray.
European Pine Sawfly HatchNormally we see European pine sawfly eggs hatch in April, but in 2014 they are just hatching on May 12 in central Maryland. The eggs were laid in the foliage in September through October. The larvae feed en masse on pine foliage.Control: Spinosad (Conserve), synthetic pyrethoids, or Acephate (Orthene) will provide control.
A close-up of a European pine sawflyPhoto: Steven Katovich, USDA Forest Service, Bugwood.org
European pine sawflies defoliating a pine branchPhoto: Forest Bowen, Wood Acres Tree Specialists
Azatin for Emerald Ash BorerWe received an email from Jeff Picher on the Azatin article. Jeff noted that Rainbow Treecare is no longer distributing this product. He suggested anyone looking for this product directly contact Paul Bolan at Bioforest for product information.
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Emerald Ash BorerMDA has published a map of the areas in which emerald ash borer has been found. They suggest that if you are within 15 miles of the area of known infestation (buffer zone) that valuable trees should be treated to prevent emerald ash borer from killing the ash trees.
For a larger view of this map, get the pdf file at: http://mda.maryland.gov/plants-pests/Documents/15_Mile_Buf-fer_Complete.pdf
Black locusts (Robinia pseudoacaia)are coming into bloom throughout the area. Emerald ash borer adults are active when black locusts are in full bloom.
Looking for Something Positive about Emerald Ash Borer?By: Stanton Gill
To find out if there is a glimmer of light with the emerald ash borer I asked for advice from parts of the country that have had this pest the longest. This week, I spoke with entomologist David Smitley, Michigan State University, about how the green and white ash trees are doing in the southern part of Michigan. From 2004 to 2013, southern Michigan suffered heavy losses of ash trees to the emerald ash borer. Valuable trees that were treated with insecticides and survived are now doing fairly well. David attributes this improving situation to the fact that all of the untreated trees are dead and have been removed from landscapes. There is less food for which the emerald ash borers can feed and thus less population pressure on surviving trees. Dr. Smitley commented that they are finding surviving trees treated with imidacloprid can now often go 2 – 3 years before another treatment is needed. Trees treated with the systemic insecticide emamectin benzoate can often go 3 – 5 years before needing retreating with this lower emerald ash borer population pressure.
Also on the positive side many of the alternatives to ash tree species that were planted are filling in well and providing shade again in neighborhoods. In East Lansing the city decided to use at least 3 different tree species on street plantings, alternating different species next to each other in the city blocks. So far, it appears to be working well with this plant diversity.
An Emerald Ash Borer Look-a-likeFrank Fogle, The Davey Tree Expert Co, found a metallic green beetle in Hunt Valley. It is the six spotted green tiger beetle which is a predator. This fast-flying beetle is often found along open paths in wooded areas.
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Scale Updates* Pine Needle Scale, Chionaspis pinifoliae (armored scale)Monitoring pine needle scale on Pinus mugo in Bowie on Monday, May 12 found the beginning of the first generation CRAWLERS! The Degree Days in Bowie were 255 DD. If degree day accumulations in your area are close or above 255 DD, you should closely monitor plants infested with pine needle scale. If crawlers are active and populations are high enough to warrant control, it is time to treat. Crawlers will seek feeding sites on the previous year’s foliage. Once they have inserted their mouth parts through a stoma, they remain at the site for the rest of their lives. Settled crawlers are flattened and yellow. Cast skins are retained and become part of the scale’s cover Control: Many lady beetles and parasitic wasps feed on this pest; therefore, careful monitoring of predators and parasitoids, as well as using pesticides with little effect on beneficials, can allow biological control to suppress the population. However if control is warranted, use a summer rate of horticultural oil or an insect growth regulator (IGR) such as Distance or Talus to target crawlers. White Prunicola Scale (WPS), Pseudaulacaspis prunicola (armored scale)Monitoring white prunicola scale on Prunus × yedoensis (Yoshino cherry) in Laytonsville on Tuesday,May 13 found females with eggs but NO crawlers. Degree Days in Laytonsville on Tuesday were 338 DD. We will continue to monitor this scale and let you know when crawlers are active. Pine Oystershell Scale, Lepidosaphes pini (armored scale)Monitoring pine oystershell scale (also called Oriental pine scale) on Pinus densiflora (Japanese red pine) in Laytonsville found females with eggs but NO crawlers. As of Tuesday May13 the Degree Days in Laytonsville were 338 DD. We will continue to monitor this scale and report when crawlers are active. Oak Lecanium Scale, Parthenolecanium quercifex (soft scale)Monitoring of oak lecanium scale on Quercus phellos (willow oak) on Monday May 12 in College Park found 80% of all females were loaded with eggs. There was NO crawler activity at this time. Degree days in College Park as of Monday were 255 DD. Rob Meier, brought in a honeylocust sample from Anne Arundle County with lecanium scale. The females were humping up and a few eggs found, but no crawlers yet. We will continue to monitor and let you know when crawlers are active. Cottony Camellia Taxus Scale, Pulvinaria floccifera (soft scale)Marie Rojas, IPM Scout, reported that this scale is starting to produce cottony egg sacs in Annandale, VA on May 15. Tony Murdock, Fine Pruning, sent in a sample from Ijamsville with a population that was of overwintering females starting to hump up to produce wax. Monitor this scale closely for egg sacs followed by the crawlers.
*Degree data totals as per Weather Channel website (http://www.weather.com/outdoors/agriculture/growing-degree-days/USMD0045)
Cottony camellia taxus scale with females producing egg sacs
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Fourlined Plant BugMarie Rojas, IPM Scout, found fourlined plants bugs damaging herbs in Cabin John on May 15. This bug feeds on over 250 species of herbaceous and woody plants. There is only one generation of this insect per year. Damage occurs early and plants grow out of it through the season. Monitoring: Look for white to dark colored spots on the foliage with plant damage concentrated on the upper foliage of the plant. The fourlined plant bug is a sucking insect that injects a toxin that discolors the foliage.Control: If necessary, this pest is easily controlled by insecticidal soap or neem products. Acephate (Orthene) is also effective.
Fourlined plant bug adult and heavy damage on foliage
Ambrosia Beetle UpdateOn May 13, we heard from a grower who was finding frass tubes on paperbark maple (Acer griseum). We have not recorded it on this species in Maryland before. Also, a grower treated trees with frass tubes with Onyx and found that beetles backed out of the holes and fell to the ground.
From Chris Ranger, PhD, Research Entomologist USDA-Agricultural Research ServiceWooster, OH: This past Sunday a grower reported attacks on trees he suspected may have been winter injured. I examined the trees yesterday. Only certain species/cultivars were attacked, and the attacked trees were often clustered, which we have seen before. Several of the attacked trees exhibited cracking, but not all of the cracked trunks were attacked. Below are the details of the attacked trees in Ohio.
Acer rubrum ‘Columnare’, Acer saccharum ‘Bailsta’, Acer saccharum ‘Green Mountain’, Celtis occidentalis ‘Chicagoland’, C canadensis ‘Applachian Red’, Quercus x Kindred Spirit® ‘Nadler’, and Tilia ‘Sterling Silver’.
Crape Myrtles – Attacked by Ambrosia BeetlesChris Erb, Complete Lawn Care, sent in these pictures of a crape myrtle in Laytonsville infested with ambrosia beetles. When we put out the ambrosia beetle alert on Friday we ended up receiving several reports of activity on several species of plants including Carpinus, European beech, Japanese maples and now – crape myrtle.
Frass tubes (left) and weeping (right) caused by ambrosia beetles infesting a crape myrtlePhotos: Chris Erb, Complete Lawn Care
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Different larval stages of the imported willow leaf beetle
Black Walnut Twig Beetle and Thousand Cankers Disease From: Walnut twig beetle/Thousand cankers work group
It’s in Maryland: Black walnut twig beetle has been found in Maryland, bringing a high risk of thousand cankers disease, known to kill black walnuts. Information on the beetle and disease is at www.thousandcankers.com. The beetle has been found only in Cecil County, but may be moving into other parts of Maryland from known infestations in adjacent states.
Help track it: Arborists and landscapers can contact Stanton Gill at Central MD Research and Education Center- 301-596-9413, [email protected]. Homeowners and master gardeners can report suspected beetles or cankers to University of Maryland Home and Garden Information Center http://extension.umd.edu/hgic/invasives/invasive-diseases 800-342-2507 or use the reporting app. Locations can be reported on MAEDN (MidAtlantic Early Detection Network iphone or android app on www.eddmaps.org/midatlantic).
Slow the spread: Do not move ANY wood (boles, chips, or trimmings) away from suspected diseased trees. Dispose of debris by burning according to local rules for air quality (contact local health department) and open air burning regulations (contact local Maryland Forest Service office). Chips can be hot composted if incorporated into the active, turned compost pile immediately. Beetles can emerge from a waiting chip pile for 2 months, so delays in disposal risk further spread of the beetle and disease.
Check state quarantines: If you are selling walnut products, be aware that many states now have quarantines; check state quarantines at state agriculture department websites before attempting to ship walnut to another state. Kiln dried or fumigated wood may be allowed; the measures used to control emerald ash borer (60 °C core temperature for 60 min.) will also control walnut twig beetles.
Imported Willow Leaf BeetleDamian Varga, Scientific Plant Service, found imported willow leaf beetles in Ellicott City on weeping willow on May 8. Feeding by the adults results in shothole type defoliation, and larvae feed in groups and cause skeletonization. These beetles commonly feed on willow and cottonwood species.Control: Depends – if the willow is in a highly visible location in the landscape you may choose to spray the tree. If it is in a natural setting and your customer can live with skeletonized leaves then the tree will not die from the damage, but it will be unattractive. Doing nothing is ok if the plant is not a specimen in the landscape.
Lace Bugs on Serviceberry and LindenMarie Rojas, IPM Scout, found lace bug adults on May 8 on Amelanchier ‘Autumn Brilliance’ and Tilia tomentosa ‘Sterling Silver’. The adults overwinter in leaf litter.Monitorng: Look for stippling damage on foliage of old growth. Damage on new growth indicates eggs havehatched and the new generation has started to feed.Control: Monitor for predators to help determine if treatment is necesssary. Lace bugs can be controlled by treating with horticultural oil but thorough coverage of underside of the foliage is necessary. Since it is finished blooming, another option is a soil drench or basal bark spray of dinotefuran which will be used up in 6 - 8 months so it won’t be in the plant when it blooms next year.
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Scab and Rust By: Karen RaneThe weather pattern this week was very favorable for a number of fungal diseases, including apple scab and Gymnosporangium rust. Both diseases were described in the April 25 issue of this newsletter. If fungicides have not yet been applied to scab-susceptible crabapple cultivars, expect to see significant infection and symptom development in the days ahead. Of course, the best way to manage these diseases in the landscape is to plant resistant cultivars – something to recommend if clients are considering new plantings. A list of cultivars resistant to scab can be found in Penn State University’s fact sheet on crabapple diseases.
Woolly Aphids on HawthornCraig Greco, Yardbirds, Inc., Marie Rojas, IPM Scout, and Nancy Harding, UMD Lab Technician, are finding woolly aphids on hawthorns this week. The aphids cause the foliage to curl and turn purplish red.
Maple Eyespot GallKatie Grant, a landscaper on the Eastern Shore, found maple eyespot gall caused by the midge Acericeris ocelliaris. The midge causes a raised area on the leaf where the insect larva feeds. A disease causes similar spotting, but there will not be a raised area present. No control is necessary.
Damage and different stages of the woolly aphidsPhotos: Nancy Harding, UMD
Early stage of maple eyespot gallPhoto: Katie Grant
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This adult two-spotted stink bug is feasting on a Colorado potato beetle larvae. That beetle will not be eating any more potatoes. Photo: M. Raupp, UMD
Beneficial of the Week By: Paula ShrewsburyThis colorful stink bug is also a predator Last week I discussed the predatory spined soldier bug making the point that not all stink bugs are bad and that some feed on pest insects. This week I want to mention another predatory stink bug, and a beautiful one at that, the two-spotted stink bug, Perillus bioculatus (Hemiptera: Heteroptera). This colorful bug is orange and black with two black spots on its pronotum just behind the head. Predatory stink bugs slowly approach unsuspecting victims and quickly stab them with their sharp beaks. The predator then injects digestive enzymes into its prey which liquefies the prey’s insides allowing the stink bug to slurp-up its meal. The two-spotted stink bug is thought to be native to the Southeastern U.S. and to have moved eastward following the dispersal of the Colorado potato beetle. The insect is presently found from Mexico into Canada. So remember when you come across stink bugs be sure to determine if it is a predator or pest.
Oakleaf blister on red oakPhoto: Karen Rane, UMD
Oak Leaf BlisterBy: Karen Rane Our first case of oak leaf blister, caused by the fungus Taphrinacaerulescens, was observed this week on red oaks in College Park. Infection occurs in early spring as buds open, causing light green, blister-like areas to develop on leaves as they expand. As they mature, the blisters develop a whitish layer on the underside of the leaf containing the spores of the fungus. Spores are splashed to the bark and bud scales, where they remain until next spring. As the growing season progresses, the blistered areas become brown. Impact on tree health is minimal, and control is usually not warranted for landscape oaks with leaf blister. In nurseries with a history of leaf blister problems, an application of a protectant fungicide such as mancozeb prior to bud break (late dormancy) may help reduce disease. Always follow label instructions when applying pesticides. Once symptoms are observed, fungicides are ineffective.
Weed of the WeekBy: Chuck Schuster, UMEBamboos are a member of the grass family. They are perennial and have about 1,200 different species. There are two basic forms of bamboo, the clumping type and the running type. Bamboos are sold in garden centers and many will purchase these plants for use as screens not realizing that some can overtake the site.
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Bamboo photos by Chuck Schuster, UME
Clumping bamboos grow in large clumps and are slower to spread. Clumping bamboo have a large root sys-tem that will compete with other plants in the landscape. Removal by digging to remove the root system is one potential method of stopping clumping bamboo. This takes time but it is a successful method. Spreading or running bamboo is much more difficult to control. This form of bamboo spreads by way of a rhizome. This form of bamboo will travel up to one hundred feet from the initial plant. Digging to remove this form of bamboo is extremely difficult if not impossible.
Control of either form of bamboo includes stressing the plant by cutting or mowing all of the plants. Bamboo is a grass and continual mowing will eventually deplete the rhizomes and will help keep it under control. Mow-ing will not totally eliminate bamboo. Mow regularly starting in the early spring; allow the plant to re-grow in late July and early August. By allowing the bamboo to regrow, valuable blade surface area for an herbicide treatment is provided. In mid to late August use glyphosate herbicide treatment. One treatment will not control bamboo. Follow-up in the next year is required. Remember that glyphosate is a non-selective herbicide and it will injure or kill all plant material on which it is used. In grassy areas where the desire is to not destroy the grass consider that bamboo can be suppressed with selective grass herbicides such as fluazifop-p (Fusilade II, Ornamec, or Grass-B-Gon) or clethodim (Envoy).
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Degree Days (As of May 15) 2014 2013 2012 2014 2013 2012Baltimore, MD (BWI) 372 342 616 Dulles Airport 361 383 620Frostburg, MD 176 182 336 Martinsburg, WV 383 340 587National Arboretum 570 486 799 Reagan National 570 486 799Salisbury 515 451 684 St. Mary’s City 426 409 717
To check degree day (DD) accumulations in your local area go to: http://www.weather.com/outdoors/agriculture/growing-degree-days/USMD0100
Note: degree days reported in this newsletter for various pests use the Weather.com web site, a base temperature of 50 °F, a start date of January 1st, and the date of monitoring as the end date.
PLANT PLANT STAGE (Bud with color, First bloom, Full bloom, First leaf)
LOCATION
Baptisia australis First bloom Ellicott City (May 15)Chrysogonum virginianum Full bloom Ellicott City (May 11)Cornus kousa Bud Ellicott City (May 15)Rhododendron atlanticum First bloom Silver Run (May 16)Rhododendron austrinum Full bloom Silver Run (May 16)Rhododendron minus var Chapmanii First bloom Silver Run (May 16)Rhododendron prinophyllum First bloom Silver Run (May 16)Rhododendron ‘Buzzard’ Bud with color Silver Run (May 16)Rhododendron ‘Klondyke’ Bud with color Silver Run (May 16)Rhododendron ‘Snowbird’ First bloom Silver Run (May 16)
Plant of the WeekBy: Ginny Rosenkranz, UMERhododendron ‘Roseum Elegans’ is a beautiful evergreen shrub that grows 6-8 feet tall and is cold hardy from USDA zone 4-8. The evergreen leaves are glossy dark olive-green, but the main attraction is the 20 large flowers that form a bouquet or truss that cover the plant from top to bottom. The flowers themselves are funnel-shaped and about 2-3 inches across, clear rose lavender in color with a few reddish brown spots. As the flowers mature they fade to a soft pink and can last up to 2 weeks. Like most of the larger rhododendrons, ‘Roseum Elegans’ blooms after azaleas in late spring to early summer. The growth habit is dense and spreading and the plant is very tolerant of cold temperatures, heat and humidity. ‘Roseum Elegans’ should be planted in a shady or woodland setting with filtered light and out of direct wind. They prefer to grow in moist, but well drained acidic soils that are high in organic matter with at least 1-2 inches of mulch to retain moisture. During periods of drought, rhododendrons, with their shallow root systems, need to be watered at least once a week with soaker hoses. Providing adequate water during the growing season and especially in very hot weather will decrease the slow decline to which older rhododendrons are often subjected. Disease problems include root rot, blight and dieback and insect pests include lace bug, mites, scale and borers.
Rhododendron ‘Roseum Elegans’Photo: Ginny Rosenkranz, UME
Stanton GillExtension Specialist
Paula Shrewsbury Extension [email protected]
Ginny RosenkranzExtension [email protected]
Chuck SchusterExtension Educator
Karen Rane Plant [email protected]
Andrew RistveyExtension [email protected]
David ClementPlant Pathologist
hgic.umd.edu
The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied.
CONTRIBUTORS:
University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.
Thank you to the Maryland Arborist Association, the Landscape Contractors Association of MD, D.C. and VA, the Maryland Nursery and Landscape Association, Professional Grounds Management Society, and FALCAN for your
financial support in making these weekly reports possible.
Photos are by Suzanne Klick or Stanton Gill unless stated otherwise.
Upcoming ConferencesMaryland Arborist Assocation Pest WalkMay 28, 2014 (afternoon to early evening)Location: Stevenson UniversityContact: MAA, 410-321-8082, [email protected]
Procrastinators’ Pesticide Applicators ProgramJune 6, 2014Location: Montgomery County Extension Office, DerwoodContact: Chuck Schuster, 301-590-2807, [email protected]
Procrastinators’ Pesticide Applicators Program - Eastern ShoreJune 13, 2014Location: Wye Research and Education Center, Queenstown, MDContact: Ginny Rosenkranz, 410-849-6141, [email protected]
MGGA Field DayJune 19, 2014 (afternoon through early evening)Location: Tidal Creek Growers, Davidsonville, MD
MNLA Field DayJune 26, 2014Location: Roseland Nurseries, Sudlersville, MD
Maryland Christmas Tree Association Summer MeetingJune 28, 2014Location: Gaver Tree Farm, 5501 Detrick Road, Mt. Airy, MD 21771Contact:301-865-3515 or [email protected]
Greenhouse Biocontrol ConferenceAugust 6, 2014 Location: Maritime Institute, Linthicum, MD
Stormwater Management ProgramAugust 20 and 21, 2014
TWO Locations: August 20 - Montgomery County Extension Office, Derwood, MDAugust 21 - Robinson Nature Center, Columbia, MD
