apple scab presentation
DESCRIPTION
TRANSCRIPT
Apple ScabDisease
aPlant
Pathology Presentation
byLisa K. Schlag30 November 2006
Apple Scab: IntroductionFor centuries, apple scab has been a disease problem plaguing
susceptible species and cultivars in the Malus genus.
A painting by Italian artist Michelangelo Merisi Caravaggio, Basket of Fruit, 1596, depicts scab-infected apples.
Apple Scab: Introduction
A painting by American artist James Peale, Fruit Still Life with Chinese Export Basket, 1824, depicts scab-infected apples.
Apple Scab: IntroductionApple scab, caused by the fungus Venturia inaequalis, is still
one of the most serious and economically important diseases of susceptible species and cultivars in the Malus genus that
exists worldwide.
In the United States, it is especially severe in the northeastern and north central states where cool, moist spring and summer weather favors the causal fungal pathogen.
significant defoliation for 2-3 years causes a general weakening or loss of vigor that could result in:
♦ increased winter injury; and
♦ susceptibility to secondary diseases and insects.
Disease losses attributable to apple scab if scab control measures are not taken
reduction in amount and quality of marketable appleharvest.poor fruit bud development for next year.
Apple Scab: Introduction
http://ohioline.osu.edu/hyg-fact/3000/3003.html
Est. Production Value losses if control measures are not taken
Apple Scab: Introduction
0
5
10
15
20
25
OH Ttl PV of Apple Crop (inmillions)
14.858 no data 20.296 18.76 24.66 27.4
Ttl PV less 70% disease loss (inmillions)
4.457 no data 6.088 5.628 7.398 7.289
1999 2000 2001 2002 2003 2004(est.)
OH
Tot
al P
rodu
ctio
n:
ww
w.e
rs.u
sda.
gov/
publ
icat
ions
/fts
/sep
04/F
TS3
12.p
df
70%
cro
p lo
ss: (
Vol
k, 2
002)
Disease losses attributable to apple scab if scab control measures are not taken
reduction in crabapples aesthetic appeal and wildlife valuecaused by premature defoliation and fruit drop.
Apple Scab: Introduction
www.apsnet..org
V. inaequalis is an Ascomycetes sac fungus producing both sexual and asexual spores
ascospores are sexual spores that initiate one primary cycle of apple scab disease annually♦inaequalis named for unequal-
sized brown “footprint”shapedtwo-celled sporesconidia are asexual spores that initiate one or more secondary cycle(s) of apple scab disease annually♦ cycle name Spilocaea pomi
www.caf.wvu.edu/kearneysville/disease_descriptions/disease_images/F7a.jpg
Apple Scab: Disease CyclePathogen
ww
w.a
psne
t.or
g
V. inaequalis belongs to the group of pathogenic fungi known as hemitrophes
parasitic phase is spent as mycelium and spores onliving tissue penetrating only the cuticle and staying between cuticle and epidermal cells.
Apple Scab: Disease CyclePathogen
www.agf.gov.bc.ca/cropprot/tflpm/applescb.htm
V. inaequalis belongs to the group of pathogenic fungi known as hemitrophes
saprophytic phase overwinters as psuedothecia initialpenetrating dead leaf tissue of fallen debris.
Apple Scab: Disease CyclePathogen
(Wilcox, 2001)
♦ Dormant ◊ before growth starts in spring
♦ Green Tip (Early April)◊ when buds start to break, showing green color of new
leaves♦ Tight Cluster - buds short-stem’d & closely pack’d (End of April)♦ Pink (Early May)
◊ when flower buds start showing color of petals♦ Bloom (Mid-May)
◊ when flower buds open♦ Petal Fall (Mid- to Late May)
◊ when flowers drop their petals♦ First, second, and third cover
◊ 10-14 days after petal fall (End of May)◊ 10-14 days after first cover (Early June)◊ 10-14 days after second cover (End of June)
Apple Scab: Disease CycleGrowth Stages of Northern Ohio Malus sp.
ww
w.ip
mce
nter
s.or
g/cr
oppr
ofile
s/do
cs/o
happ
les.
htm
l
Movement of fungal pathogen V. inaequalis is passivemoisture must be present to induce expulsion of ascospores from psuedothecia
♦ ascospores disseminated by splashing rain and wind
♦ few spores mature at green tip with maturity progressing slowly until tight cluster
♦ discharge usually peaks between stages pink through bloom, and nearly all discharged within 2-4 weeks after petal fall
conidia disseminated by rain, washed or splashed, and/or wind
Apple Scab: Disease CycleDissemination
Primary inoculum♦ ascospores forcibly released by asci into air
when mature pseudothecia become thoroughly wet during spring rain
♦ discharged over a 5-9 week period◊ starting at bud break (green tip) and peaking
from pink to petal fall stages
Secondary inoculum♦ conidia arise from primary and secondary lesions
when humidity levels are at least 60-70%♦ discharged over growing season
◊ throughout remainder of growing season
Apple Scab: Disease CycleInoculation
V. inaequalis is a nonobligate hemitrophe
direct penetration
♦ascospores and conidia develop fine hyphae which directly pierces cuticle and grows in a subcuticular position between cuticle and epidermal cells
◊ fungus may degrade and use cuticle as well as some host cell wall and pectic materials for nutrients
◊ once leaves fall to ground, mycelium penetrates tissue below existing lesions
does not always lead to infection
Apple Scab: Disease CyclePenetration
V. inaequalis spores require a film of water on plant tissue for a specific period of temperature-dependent time to germinate
and infect susceptible Malus sp. hosts
infections affected by age of leaves and fruit
♦ leaves most susceptible 1-5 days after unfolding
♦ fruit most susceptible until 3-4 weeks after petal fall
♦ leaves and fruit become less susceptible with maturity
Primary scab infection
♦ occurs from bud break until 2-4 weeks past petal fall
Secondary scab infection(s)
♦ can occur several times during growing season when suitable conditions prevail
Apple Scab: Disease CycleInfection
Apple Scab: Disease CycleInfection -- Revised Mills Table
ww
w.n
ysae
s.co
rnel
l.edu
/pp/
exte
nsio
n/tf
abp/
com
pone
nts
/rev
mill
s.ht
ml
1A
vera
ge te
mpe
ratu
re d
urin
g th
e w
etti
ng p
erio
d in
Fah
renh
eit o
r C
elsi
us2 M
inim
um w
etti
ng p
erio
d ne
eded
to a
chie
ve in
fect
ion
3 Tim
e in
day
s un
til v
isib
le s
ympt
oms
appe
arAverage Temperature1
Fº Cº Wetting Period (hr)2
79 26 11.3 --
77 25 8 --
75 24 6.1 --
73-63 23-17 6 9-10
61 16 6.1 9-10
59-57 14-15 7 12-13
55 13 8 14
54 12 8.3 14
52 11 9 15
50 10 11 16
48 9 12.2 17
46 8 13.4 17
44 7 15.4 17
43 6 18 17
40 5 21.2 --
39 4 27.8 --
37 3 29.6 --
35 2 34.7 --
34 1 40.5 --
IncubationPeriod (days)3
Apple Scab: Disease CycleInfection -- Revised Mills Table
Mills Curves
♦ 1944, first attempt at using forecasting to help growers time applications of sulphur dusts
♦ relates hours of leaf wetting and temperature during wetting period to scab infection
Revised Mills Table – reflects most up to date information♦ shorter times for infection by ascospores and conidia♦does not rate severity of infection periods◊ rating severity on wetness duration misleading◊ other factors important – suceptibility; inoculum level
♦ day vs night ascospores◊ over 95% of ascospores not released until after sunrise◊ conidia not affected by light or darkness
www.nysaes.cornell.edu/pp/extension/tfabp/mills.shtml
Primary scab cycle♦ by late winter or early spring, each
mature, flask-shaped pseudothecia produces 50-100 asci with each ascicontaining 8 ascospores
◊ first ascospores become mature about bud break
♦ within 9-17 days of primary infection, ascospore lesions produce conidiophores which bear 10,000’s+ of potentially infectious secondary scab spores called conidia
These produce, produce, produce… additional conidiaphores and conidia in fall, V. inaequalis colonizes tissues beneath former scab lesions producing pseudothecia during dormant season
Apple Scab: Disease CycleGrowth & Reproduction
ww
w.c
af.w
vu.e
du/k
earn
eysv
ille/
wvu
farm
8.ht
ml
Secondary scab cycle♦ conidia form olive-green to
brown, velvety textured scab lesions that push up through the cuticle
♦ can continue throughout the spring, summer, and autumn
♦ in autumn, V. inaequaliscolonizes tissues beneath former scab lesions producing pseudothecia initial during dormant season
Apple Scab: Disease CycleGrowth & Reproduction
ww
w.a
psne
t.or
g(c
ited
: slid
e 8)
Apple Scab: Disease CyclePrimary scab cycle
Secondary scab cycle
Polycycl
ic
Disease
(Agrios, 2005)
In Spring, symptomatic spots (lesions) are most noticeable on leaves and fruit; however, symptoms of V. inaequalis infection can also appear on:
♦ petioles;
♦ pedicels;
♦ apple blossoms;
♦ bud scales; and
♦ young twigs/shoots
Apple Scab: SymptomsSusceptible Plant Parts
In spring, first spots (lesions) usually located on lower surface of expanding leaves
Apple Scab: SymptomsLower Leaf Surface
(Wilcox, 2001)
Lesions progress to olive-green to brown coloration and velvety texture. As fungal growth stops the lesion margins
change from feathery, indistinct to distinct
Apple Scab: SymptomsUpper Leaf Surface
www.uni-kl.de/FB-Biologie/AG-Hahn/Research/venturia%20engl.html
Scab sheet is a condition whereentire leaf surface is coveredwith apple scab disease
Apple Scab: SymptomsUpper Leaf Surface
later yellowing stage
www.ppdl.purdue.edu/ppdl/weeklypics/Weekly_Picture6-10-02-1.html, Gail Ruhl
circular, necrotic olive-green or brown colored warty lesions with distinct margins on fruit infected early in development
Apple Scab: SymptomsFruit
fruit infected late in season small black spots of “pinpoint” scab noticeable after harvest apples in storage
www.caf.wvu.edu/kearneysville/disease_descriptions/disease_images/photo2-9.jpg
Small, dark green lesions on pedicel before, during, or after bloom
www.caf.wvu.edu/kearneysville/disease_descriptions/disease_images/AppleScabPedicel.jpg
Apple Scab: SymptomsPedicel just after Petal Fall
Natural♦ disease-resistant Malus sp. cultivars ♦ biological♦ environment
Cultural♦ sanitation♦ pruning♦ growing practices
Chemical♦ protectant (protective) fungicides♦ post-infection (suppressant) fungicides
Integrated Pest Management
Apple Scab: Disease ControlTreatments
create environment unfavorable for pathogen
Apple Scab: Disease ControlTreatments
Flail mower chopping leaf debris Airblast sprayer applying fungicides
ww
w.a
psne
t.or
g
ww
w.a
psne
t.or
g
Leaf wetness monitor Mills Table-based weather monitoring systemorch
ard.
uvm
.edu
/uvm
appl
e/pe
st/b
ackt
obas
ics/
dise
ases
/sca
b.ht
m
Plant disease-resistant Malus sp.cultivars♦ best means of managing apple scab on crabapples♦ fresh market apples not as popular♦ disease resistancy may be temporary
◊ through sexual reproduction, V. inaequalis can overcome resistance
biological♦ New Zealand -- yucca extract prevents germination of
fungus and had curative effect ♦ antagonistic fungi may decrease ascospore
production -- viable option in futureenvironment♦ humidity < 60% and drier weather conditions
Apple Scab: Disease ControlNatural
top varieties of fresh market apples grown in Ohio1 vary intheir susceptibility to apple scab disease:
Very susceptible Moderately susceptible
♦ Red Delicious ♦ Golden Delicious
♦ Rome Beauty ♦ Jonathan♦ McIntosh
while some are highly resistant and immune to scab and well suited to organic commercial & backyard growers:
♦ Enterprise ♦ Liberty ♦Priscilla
♦ Freedom ♦ Macfree ♦ Redfree
♦ Gold Rush ♦ Nova Easy ♦ Sir Prize♦ Jonafree ♦ Prima ♦ William’s Pride
1www.ipmcenters.org/cropprofiles/docs/ohapples.html
Apple Scab: Disease ControlNatural
All require fungicide
usage
ohioline.osu.edu/hyg-fact/3000/3003.html
crabapple cultivars with excellent scab resistance and
superior horticultural characteristics for Ohio, including
being small-fruited for wildlife:
♦ Malus baccara ‘Jackii’ ♦ Red Jewel ♦ Silver Moon
♦ Bob White ♦ Royal Splendor ♦ Strawberry Parfait♦ Ormiston Roy ♦ Malus sargentii ♦ Sugar Tyme
♦ Prairifire ♦ Sentinel ♦ Malus x zumi‘Calocarpa’
crabapples initiate buds for next season mid-June to early July
Apple Scab: Disease ControlNatural
Create unfavorable environment for pathogenreduce occurrence of primary innoculum♦ collect & destroy all fallen leaves♦ dolomitic lime or 5% urea applied to ground of fallen
leaves hastens leaf decomposition♦ flail mowing to chop leaf litter in autumn decrease drying time of plant tissues during growth♦ prune to increase sunlight penetration into and
improve air movement through tree canopy♦ avoid overhead irrigation
◊ irrigate soil around treesplant right tree in right location♦ plant new trees in well-drained, sunny locations♦ pathogens can attack healthy plants
Apple Scab: Disease ControlCultural
no chemical treatments were employed until the
late 1800’s
♦ at that time, cooper- and sulphur- based fungicides
were used as pre-infection protection.
◊ these treatments caused substantial foliar damage
cultural practices influence fungicide usage
♦ fungicides are not an alternative to the use of sound cultural practices
standard Malus sp. cultivars vary widely in their susceptibility to scab
♦ influences intensity of control program
Apple Scab: Disease ControlChemical
Apple Scab: Disease ControlChemical -- Fungicides
Protectant -- 5-7 day spraying schedule in early season
♦ prevent spores from germinating or penetrating leaf tissue
♦ must apply to susceptible tissue before infection occurs
◊ green tip & 1 week past petal fall critical time
Post-infection – every 7-10 days later in season
♦ penetrates tissue to eliminate/inhibit lesion development
♦ effectiveness limited to few hours/days depending on
fungicide
monitor rainfall in orchard
♦ 1/2”-1” rain needed to deplete half fungicide residue on
fruit and foliage
Apple Scab: Disease ControlChemical -- Fungicides
www.ipmcenters.org/cropprofiles/docs/ohapples.html
green tip x x xtight cluster x x x xpink x x xbloom x x x xpetal fall x x
3d cover x xremaining x x
1st & 2d cover x x x x
dormant x x
capt
an
ferba
m
lime
sulp
hur
man
coze
b
thio
phan
ate
-meth
yl
myc
lobutan
il
Fungicide selection should be based on:♦ other diseases that must be managed♦ scab fungus resistance♦ history of disease in orchard or property landscape♦ final market for fruit♦ other social and economic factors
Multi-purpose sprays containing insecticides andfungicides are convenient , but have disadvantages
♦ none controls all insects and diseases ♦ lack flexibility◊ only use after bloom period to prevent lethal harm
to bees; fungicides alone are not harmful to bees♦ more expensive than chemicals you prepare
Apple Scab: Disease ControlChemical -- Fungicides
Integration of all available control methodsEffective disease management program should emphasize integrated use of:
♦ knowledge of pathogen and disease;
♦ disease resistant plants;
♦ specific cultural practices; and
♦ timely application of chemicals when needed.
◊ weather monitoring equipment and disease forecasting computer programs can predict scab infection periods
▪ Envirocaster ; Metros
Apple Scab: Disease ControlIntegrated Pest Management (IPM)
Agrios, G.N. (2005). Plant Pathology (5th ed.) Burlington, MA:Elsevier Academic Press.
Cloyd, R.A., Nixon, P.L., & Pataky, N.R. (2004). IPM for Gardeners:A Guide to Integrated Pest Management. Portland, OR: Timber
Press.
Dirr, M.A. (1998). Manual of Woody Landscape Plants (5th ed.)(pp. 630-660). Champaign, IL: Stipes Publishing.
Sinclair, W.A., & Lyon, H.H. (2005). Diseases of Trees and Shrubs (2nd
ed.)(pp. 86-87). Ithaca, NY: Cornell University Press.
Apple Scab: ReferencesBooks
Apple Scab (April 2006). Retrieved 2 Nov. 2006, from Cornell University, Plant Disease Diagnostic Clinic Web site:http://plantclinic.cornell.edu/FactSheets/apple_scab_factsheets/apple_scab.htm
Apple Scab. Retrieved 17 Nov. 2006, from New York State IPM Program, from Cornell Cooperative Extension Web site:www.nysipm.cornell.edu/factsheets/treefruit/diseases/as/as.asp
Apple Scab of Flowering Crabapples (March 2002). Retrieved 20 Nov. 2006,Bull.BP-39-W,from Purdue University Cooperative Extension Service Web site.
Biggs A.R. & Hickey K.D. Apple Scab. Retreived 20 Nov. 2006, from NYS IPM TreeFruit Factsheet, New York State Agricultural Experiment Station Web site:http://www.nysaes.cornell.edu/pp/extension/tfabp/apscpm.shtml
Chatfield J.A., Draper E.A., Cochran K.C., Bristol P.W., & Tubesing C.F. (1999).Ornamental Plants – Annual Reports and Research Reviews 1999. Retrieved 7 Nov. 2006,from Ohio State University, Ohioline Web site:http://ohioline.osu.edu/sc173/sc173_16.html
Chatfield J.A., Rose M.A., Ellett C.W.,et al.(1996). Disease Control in the Landscape.Retrieved 10 Nov. 2006,Bull.614, from Ohio State University Ohioline Web site:http://ohioline.osu.edu/b614/b614.html
Apple Scab: ReferencesElectronic
Ellis M.A., Chatfield J., & Draper E. (1994). Scab of Apple and Crabapple. Retrieved 7 Nov. 2006, from Ohio State University, Ohioline Web site:http://ohioline.osu.edu/hyg-fact/3000/3003.html
EU researches promise disease-free apples (July 2006). Retrieved 21 Nov. 2006, fromFood navigator Web site:http://www.foodnavigator.com/news/printNewsBis.asp?id=69114
Grove G., & Xiao, C-L (2005). Apple Scab. Retrieved 2 Nov. 2006, from WashingtonState University Extension Web site:http://cru.cahe.wsu.edu/CEPublications/pnw0582/pnw0582.pdf
Hartman J.R.(June 1996). Apple Scab. Retrieved 2 Nov. 2006, from University of Kentucky, Cooperative Extension Service Web site:http://www.ca.uky.edu/agc/pubs/ppa/ppa24/ppa24.pdf
Schroeder D.B. Marrotte E.L. (Ed.), Apple Scab (February 2003). Retrieved 7 Nov. 2006, from University of Connecticut, Integrated Pest Management Web site:http://www.hort.uconn.edu/ipm/homegrnd/htms/19apscab.htm
Turechek J. & Carroll J., The Mill’s Table. Retrieved 27 Nov. 2006, from New York State Agricultural Experiment Station Web site:http://www.nysaes.cornell.edu/pp/extension/tfabp/mills.shtml
Apple Scab: ReferencesElectronic
Volk, T. (2002). Tom Volk’s Fungus of the Month for September 2002. Retrieved 7 Nov. 2006, from University of Wisconsin-La Crosse, Tom Volk Fungi Web site:http://botit.botany.wisc.edu/toms_fungi/sep2002.html
Wilcox W.F. Apple Scab. Retrieved 17 Nov. 2006, from New York State Integrated Pest Management Web site:
www.nysipm.cornell.edu/factsheets/treefruit/diseases/as/as.asp
Wilcox W.(2001). Apple Scab. Retrieved 20 Nov. 2006, from NYS IPM Tree Fruit Factsheet, New York State Agricultural Experiment Station Web site:
http://www.nysaes.cornell.edu/pp/extension/tfabp/apscpm.shtml
The American Phytopathological Society web site presents information on many plant diseases and their control. Retrieved 31 October 2006.
www.apsnet.org
Apple Scab: ReferencesElectronic