diseases of roses john & mitchie moe ars master rosarians pacific northwest district revised...
TRANSCRIPT
![Page 1: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/1.jpg)
Diseases of Roses
John & Mitchie MoeARS Master Rosarians
Pacific Northwest District
Revised March 2015May 25, 2012
![Page 2: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/2.jpg)
This program is eligible for one CR Credit if pre-approved by the District and National CR Chairs
An American Rose Society Presentation © 2015
![Page 3: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/3.jpg)
Acknowledgements
• Most photos used in this program are copyrighted.
• Permission was received to use the copyrighted
photos for this educational program! Please do not
copy or reproduce for any other uses.
• An excellent source – the ARS Consulting Rosarian
Manual
• Another excellent source - http://www.sactorose.org
Baldo’s Bugs & Roses, the website of Baldo
Villegas, known to rosarians as “The Bugman”• Please – no commercial use of this program!
![Page 4: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/4.jpg)
Introduction
• There are many diseases of roses that have described in various books, but there are three that seem to afflict the rose garden at one time or another:
• Mildew• Blackspot• Rust
• If these three can be controlled, the rose garden will be generally disease free. They can often be managed by following these recommendations:
• Buy certified stock free of diseases• Keep free of weeds, fallen leaves, and disease-infested plants or
canes• Use regular spray programs, and practice good cultural methods
Note: This program deals primarily with identification of diseases, and does not get into specific chemical controls, which is a subject by itself.
![Page 5: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/5.jpg)
Powdery Mildew
• A very common disease of
roses – some roses more
susceptible than others!
• Starts on leaves, but spreads
to buds and young shoots
• Common in crowded plantings
where air circulation is poor
• Optimum conditions for spore
germination are 71°F and 98
percent relative humidity
Sphaerotheca pannosa
Photo by Jack Kelly Clark
Warm days and cool nights makes any climate just right for this!
Jack Kelly Clark
![Page 6: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/6.jpg)
Powdery Mildew Control
• Over-winters on infected canes, spores move to new leaves in spring to begin disease cycle
• Aggressive spring pruning will remove a large source of this fungus
• Fungicides work best at onset of disease, not after massive infection has occurred
• A regular fungicide spray program is generally necessary to prevent it
David Hughes, Gardenseeker.com
This is why the first fungicide spray is so important!
![Page 7: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/7.jpg)
Black Spot
• Small 2 mm black spots enlarging to 12 mm with generally circular appearance, but having a feathery edge found on the upper leaf surfaces as well as immature canes
• One of the most common diseases of roses
• Disease cycle typically begins on canes and leaves infected the previous season
• Leaves less than two weeks old are the most susceptible
Photo by Jack Kelly Clark
Diplocarpon rosae
![Page 8: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/8.jpg)
Blackspot (cont.)• Lower areas are more likely
to be infected as spores are
splashed up on new foliage
during rains or irrigation– will
continue up the stem - as
disease spreads, leaves go
from green to yellow and then
drop
• Becomes very active in a wet
environment with temps
around 70°F – needs about 7
hours to produce new spores
to infect additional leaves and
canes within a few days
Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org
![Page 9: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/9.jpg)
Blackspot Control• Good sanitation will help –
remove diseased leaves
• Spores can over winter on canes, and the entire cycle will repeat next year if a fungicide spray program is not started early and maintained!
• Aggressive spring pruning will remove a large source of fungus
• Prune to allow air circulation, and water without wetting the foliage
• Buy disease resistant varieties of roses
Photo by Jack Kelly Clark
![Page 10: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/10.jpg)
Rust• A fungal disease common in
many areas, easily identified
• Appears on the underside of the foliage as red-orange spots
• Thrives in cool, moist weather
• The summer stage is cyclic, and may repeat every 10 to 14 days in favorable weather
• Fungus overwinters on infected leaves and canes
• Spores are wind borne
• Can defoliate the plant
Clair Martin
Phragmidium spp
![Page 11: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/11.jpg)
Rust Control• Good sanitation will
help to prevent early season infections
• Remove affected leaves and dispose in trash
• Don’t water in the evening so that the leaf surface is wet over night
• Fungicide you use for powdery mildew or black spot is usually effective Univ of GA
![Page 12: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/12.jpg)
Downy Mildew
• A very serious disease that
can affect all roses!
• May appear when favorable
conditions of humidity over
85% and temps of 65 - 75° F
• Under cool and moist spring
conditions, young leaves,
stems and flowers may show
purple to red or brown
irregular blotches that tend to
follow the leaf veins
• Advanced infections will have
yellowing of leaves
Peronospora sparsa
Gail Trimble
![Page 13: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/13.jpg)
Downy Mildew (cont.)• White to grayish
fungal threads containing spores coat the undersides of leaves
• Spores may germinate in as little as 4 hours, and appear on leaf surfaces in 3 days
• Can defoliate a plant in a day or so
• Fungus can winter-over as spores in or on plant parts
Photo by Jack Kelly Clark
![Page 14: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/14.jpg)
Treating Downy Mildew• Once seen, it is
generally too late to prevent severe leaf drop, which begins at the top!
• Before treating, severely prune heavily infected and defoliated plants to encourage new growth
• Destroy all cut material, spores can live for a month
• Treating generally requires using some very potent and costly fungicides Gail Trimble
![Page 15: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/15.jpg)
Anthracnose
• Initially spots are small and black - easily confused with blackspot
• Spores believed to be carried by water or rain to new leaves and stems
• As disease progresses, spots become purple to brown and centers turn gray or white with dark margin
• This light-colored center best defines the difference with blackspot
• Can be severe under cool, moist spring conditions
Baldo Villegas
Sphaceloma rosarum
![Page 16: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/16.jpg)
Anthracnose (cont.)
• Tissue may drop out of the
center of the spots, giving
infected leaves its other
name of “Shot Hole Fungus”
• Fungus overwinters as spores
mainly in old lesions on
canes
• Can cause leaf drop that
weakens the plant
• In extreme cases, it can
result in complete defoliationGail Trimble
![Page 17: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/17.jpg)
Anthracnose Control
• Sanitation is best means of control – remove diseased leaves, and dispose in trash
• Plant spacing, use of drip lines or soaker hoses rather than sprinklers should help
• Prune out canes that have infections in fall – dispose in trash, not in compost pile
• Fungicide used for black spot is usually effective
Paul Bachi
![Page 18: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/18.jpg)
Botrytis Blight
• When the weather is cool and wet,
the conditions are right for this
fungus
• Most common symptom - young
flower buds droop, turn black at
the base
• Later produce
the cottony
grey-black
mycelium of
the fungus
Botrytis cinerea
Gail Trimble
Gail Trimble
• Can affect any part of the plant except roots
![Page 19: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/19.jpg)
Botrytis Blight (cont.)• Spores are moved to other
plants by wind or blowing rain
• Note the grayish fuzzy growth on the cane that indicates botrytis
• Good ventilation is also essential in reducing disease incidence
• Fungus may overwinter in dead plant material
• Remove blighted flowers, leaves, or entire plants if infected at the base – discard in trash!
• Fungus becomes quickly resistant, so alternate fungicides
Univ of GA
![Page 20: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/20.jpg)
Rose Canker• A fungal disease that
can affect any part of the plant, but most common on stems and canes
• After a cold wet winter, pruned stems provide wound sites for canker causing fungi
• Canker can also enter thru leaf scars – do NOT tear off leaves during fall pruning!
Coniothyrium spp
John Moe
![Page 21: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/21.jpg)
Rose Canker (cont.)
• Tissue within the canker begins to dry out and shrink, giving it a shriveled look
• Stems will yellow, often have red spots and later become a dark brown or black
• Can be acute on old roses that have lost vigor, and on new bare root roses coming from cold storage
John Moe
![Page 22: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/22.jpg)
Rose Canker Control• Time fall prune so tips
can callus before winter
• Dormant spray can protect pruning cuts
• Disinfect pruners before moving to another bush
• In spring, remove infected canes and spray for fungal disease
• Fungicides that control black spot will also help to control canker
John Moe
![Page 23: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/23.jpg)
Bacterial Crown Gall
• Bacterial disease usually seen on bud union, or on the trunk
• Thrives in warm, sunny weather; not active in cold weather
• Cork-like substance that will turn brown and harden as it ages
• Plants will usually be stunted in their growth habits
Agrobacterium tumefaciens
John Moe
![Page 24: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/24.jpg)
Bacterial Crown Gall (cont.)
• Can persist in the soil in a dormant state for years
• The growth can be removed, however, chances are it will eventually return
• If you do cut out galls, use a sharp knife or pruning shears, brush on full strength bleach
• Destroy the galls; disinfect cutting tools with Lysol® after each cut
John Moe
This cut was most likely made with infected pruners!
![Page 25: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/25.jpg)
Bacterial Crown Gall Control
• Avoid injury to canes and stems when planting or cultivating
• Maintain good garden sanitation and cultural practices
• If heavily infected, remove and discard the plant
• If you can, replace soil where rose was growing with new soil, or saturate the soil well with a 10% bleach solution before replanting
• Disease is un-treatable
![Page 26: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/26.jpg)
Rose Mosaic
• Probably the most commonly found virus in roses
• Mosaic is primarily transmitted by propagation
• Usually appears in spring as a distortion of growing tips and leaves
• Symptoms include coloration patterns (shown), distorted leaf growth, slow to develop, and fewer quality blooms
Univ of Georgia
Prunus Necrotic Ringspot Virus
![Page 27: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/27.jpg)
Rose Mosaic (cont.)• No cure – buy quality
plants showing no symptoms of the disease
• Commercial rose growers purchase rootstock that has been “virus indexed”, which means it has been lab tested to confirm the absence of the virus in the plants tissue
• Overall damage from the disease may be mostly cosmetic with some reduction of plant vigor
Univ of GA
Jack Kelly Clark
![Page 28: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/28.jpg)
Rose Rosette Disease (RRD)• Exact cause unknown
• The distinctive red stems, distorted and wrinkled leaves are symptoms
• The main host is R. multiflora
• New growth appears unusually soft and pliable
• RRD is suspected to be carried from plant to plant by the tiny eriophyid mite
• Can be confused with plant damage from chemicals like Roundup®
Photo by James W. Amrine Jr.
![Page 29: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/29.jpg)
Rose Rosette Disease
• The stems grow slowly and produce excessive thorns
• There may be so many thorns that the stem may be non-visible!
• Thorns are often red-tinged
Photo byJohn Hartman
![Page 30: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/30.jpg)
Rose Rosette Disease
• If you are sure that it is this disease, you need to act fast!
• Very serious disease – no cure, fatal to plant!
• Remove the diseased plant as soon as possible (including the entire root system) and destroy it!
• Considered to be one of the most damaging problems of roses!
Photo by James W. Amrine Jr.
![Page 31: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/31.jpg)
Questions?
Thank You
![Page 32: Diseases of Roses John & Mitchie Moe ARS Master Rosarians Pacific Northwest District Revised March 2015 May 25, 2012](https://reader030.vdocument.in/reader030/viewer/2022032709/56649eb55503460f94bbd6af/html5/thumbnails/32.jpg)
Program Services
Power Point programs on roses are available for download from the ARS website, “members only” section.
They are offered to our members for use by a local or district rose society or an ARS judging or consulting rosarian school.
These programs are copyright © ARS 2015.
Commercial use is strictly forbidden.