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Entomosporium Leaf and Berry Spot
Dr. Philip Ronald
Riverbend Orchards Inc.
Alberta Farm Fresh School 2013
OVERVIEW
PART I. INTRODUCTION TO ELBSPART II. DISEASE CYCLEPART III. INFECTION PROCESSPART IV. MEASURES OF DISEASE RESPONSEPART V. CULTIVAR DISEASE RESPONSEPART VI. CHEMICAL CONTROLPART VII. CULTURAL CONTROL
The Saskatoon Industry
first orchards established in 1970’s
today: 500 - 800 ha in the prairies
average yield: 3,300 - 4,500 kg per ha
challenges:
production information
demand for fruit exceeds supply
fungal diseases
Disease Triangle
I. INTRODUCTION
Entomosporium leaf and berry spot
distributed throughout temperate zones worldwide
affects genera of the subfamily Pomoideae (Rosaceae)
most serious disease facing the saskatoon industry
The Pathogen
imperfect stage:
Entomosporium mespili
causal organism
acervuli on leaves/fruit
5-celled conidiospores
perfect stage:
Fabraea maculata
rarely seen
Discomycete
2
The Host
Saskatoon –Amelanchier alnifolia
Numerous cvs
Selected from the wild
No breeding program
No disease screening
Other factors:
Suckering habit = hedge
Growing out of range
Foliar Symptoms
first evidence
starts at plant base basal shoots/suckers
moves up canopy
source of 2o inoculum splashed onto fruit
symptoms: brown spots (1-3 mm)
yellow halo -> leaf
defoliation
Fruit Symptoms
greatest concern to growers
symptoms:
angular, brown spots
watery, grey lesions
cracking, shriveling
stalks may also be infected
fruit quality:
downgraded
unusable when >6% FAA
Twig Symptoms
twigs:
cankers on 1 yr wood
may be a source of 1o
inoculum
rarely persist
II. DISEASE CYCLE Disease Pathway
fungus overwinters: diseased twigs
fallen leaves
retained fruit
primary infection: conidiospores are
splashed onto new leaves
secondary infection: disease moves upwards
bounces from leaf to leaf
then leaf to fruit
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The Acervulus
site of spore production
upper leaf surface
rapid cell division 1000’s of conidiospores
leaf surface erupts
disease spread:
conidiospores 1o and 2o inoculum
splash dispersal rain / irrigation
Ideal Conditions
ELBS will flourish when weather conditions include
high relative humidity or rainfall
temperatures between 20 and 26 C
ELBS “explodes” in wet and warm weather
need for proactive control
Protect the Flowers
flowers seem to be an important stage
source of nutrition for fungus until leaves emerge?
e.g. Sclerotinia
III. INFECTION PROCESS
characterize host-pathogen interaction detached leaves of 17
saskatoon cultivars inoculated with spore
suspension of ELBS SEM microscopy
steps in infection: germination penetration invasion sporulation
Unique Spores
Unique 5 celled conidiospore with tiny bristles
Mouse-like appearance
Easy to distinguish from other spores on the leaf surface
A. Conidiospore Germination
2 dpi
2 dpi
Cell extension
using energy reserves, spore produces germ tube
seeks entry point on leaf
Germ-tube extrusion
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B. Leaf Penetration
2 dpi
Sub-spore appressorium
2 dpi
Germ-tube appressorium
using host energy, fungus moves into leaf
produces infection peg and haustorium
feeds on epidermal cells
C. Hyphal Colonization
fungus moves deeper into leaf mesophyll
sufficient network of hyphae to begin reproduction
D. Sporulation
Leaf acervulus – cross section
Conidiospore production results in an eruption on the leaf surface
Splash dispersal to other leave or developing fruit
Spore Dispersal
Mechanisms of disease resistance?
types of resistance:
passive (pre-infectional)
active (post-infectional)
resistant host may restrict:
germination (G)
penetration (P)
colonization (C)
sporulation (S)
G
P
C
S
Pre-infectional Defenses
compared Buffalo and Success
differ in severity of leaf infection
pre-penetration response
spore germination/penetration restricted on Success
possible explanations:
leaf surface properties
stimulatory / inhibitory compounds
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Conidiospore Germination/Penetration
Buffalo - S Success - R
2 dpi
5 dpi
Conidiospore Germination/Penetration
Cultivar 2 dpi 5 dpi
Germination
Penetration
Germination
Penetration
Buffalo 72% 43% 41% 54%
Success 53% 12% 45% 22%
Leaf Surface Properties
cut
Success – SEM Success - FLUOR
tri
III. MEASURING DISEASE
reliable / repeatable measures of ELBS
disease incidence qualitative – yes or no
% plants / % leaves / % fruit
sporulation / infection
disease severity quantitative – numerical measure
infection: area affected, lesion size / number
sporulation: fruiting bodies, acervuli
A. Leaf Infection
necrosis
fungal penetration
cell damage / death
variables:
percentage of leaves infected (I)
percent leaf area affected (S)
leaf lesion number/size (S)
SigmaScan software
B. Leaf Sporulation
leaf acervuli
sites of conidiogenesis
2o inoculum production
variables:
percentage leaves sporulating (I)
leaf acervuli number (S)
visual counts
dissecting microscope
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C. Fruit Infection/Sporulation
fruit infection
result of leaf inoculum
further sporulation
variables:
percentage fruit infected / sporulating (I)
fruit acervuli number (S)
visual counts
dissecting microscope
IV. CULTIVAR RESPONSE
resistance: active host response to infection
possible outcomes of inoculation:
immunity – no infection
infection leads to: complete resistance
partial resistance
complete susceptibility
Methodology
identify saskatoons with resistance to ELBS
17 saskatoon cultivars originating in AB., SK. and U.S.
replicated trials
reported resistance to ELBS Parkhill, Regent, Success
disease screening:
natural infection: leaf / fruit disease
detached leaf assay
A. Leaf Response - Natural Infection
Edmonton, 1997 10 cultivars in four replicate RCBD
sample: 50 leaves per plant
leaf infection
Hudson Bay, 1998 & 1999 15 cultivars in three replicate RCBD
sample: 40 leaves per plant
leaf infection / sporulation
Incidence of Leaf Infection (two locations)
010
20
30
4050
60
70
8090
100
% L
eaf
Infe
ctio
n
For Hon Nor Pea Pem Prk Reg Smo Suc The
ED97
HB98
HB99
Severity of Leaf Infection (two locations)
01
2
3
45
6
7
89
10
PL
AA
For Hon Nor Pea Pem Prk Reg Smo Suc The
ED97
HB98
HB99
7
Incidence of Leaf Sporulation (Hudson Bay)
0
10
20
30
4050
60
70
80
90
100
% L
eaf
Sp
oru
lati
on
Blu Buf For Hon Mar Nor Par Pea Pem Prk Reg Smo Suc The
1998
1999
Severity of Leaf Sporulation (Hudson Bay)
0
20
40
60
80
100
120
140
160
Lea
f ac
ervu
li n
um
ber
Blu Buf For Hon Mar Nor Par Pea Pem Prk Reg Smo Suc The
1998
1999
B. Detached Leaf Assay
inoculate leaves of 17 cultivars
two experiments
four replicates
five leaf ages
evaluation:
infection
sporulation
Disease on Detached Leaves
Susceptible: Buffalo
Resistant: Success
Lf 1 Lf 2 Lf 3 Lf 4 Lf 5
Severity of Leaf Sporulation
0
20
40
60
80
100
120
140
160
180
Le
af
ac
erv
uli
nu
mb
er
Blu Buf For Hon Mar Nor Par Pea Pem Prk Reg Smo Suc The
Det Lf
Nat Inf
C. Fruit - Natural Infection
Edmonton, 1997 10 cultivars in four replicate RCBD
sample: 10 racemes per plant
fruit infection
Hudson Bay & Moonlake, 1999 15 cultivars in three replicate RCBD
sample: 6 racemes per plant
fruit infection and sporulation
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Incidence of Fruit Infection (two locations)
010
203040
5060
7080
90100
% F
ruit
In
fect
ion
For Hon Nor Pea Pem Prk Reg Smo Suc The
ED-97
HB-99
Incidence of Fruit Sporulation (1999)
0
10
20
30
40
50
60
70
80
90
100
% F
ruit
Sp
oru
lati
on
Blu Buf For Hon Mar Nel Nor Par Pea Pem Prk Reg Smo Suc The
HB-JN
HB-JL
ML
Fru
it a
cerv
uli
nu
mb
er
Blu Buf For Hon Mar Nel Nor Par Pea Pem Prk Reg Smo Suc The
HB-JN
HB-JL
ML
Severity of Fruit Sporulation (1999)
0 1 2 3Distances
Bluff
Buffalo
Forestburg
Honeywood
Martin
Nelson
Northline
PAR90
Pearson II
Pembina
Parkhill
Regent
Smoky
Success
Thiessen
Cluster Analysis - Disease Response
IV. CHEMICAL CONTROL
Need varies with site
South MB = “banana belt”
Heat, humidity, rainfall
Protect your investment
$500 for $50,000
Apply at flower stage
White tip
Petal fall
Green fruit
New short PHI chemicals
Green tip
White tip
Saskatoon Berry Bloom and Bud Stages - Pests and Pest Management Hort Snacks - April 2012
Protect the flowers from rain showers
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Keep the foliage clean until harvest
Choices for Disease Control
Product name
Registration number
Common name GroupPreharvest
intervalMinimum re-entry
Maximum # applications per season
Funginex DC 27686 triforine 3 60 days 48 hours 1
Jade 24030 propiconazole 3 38 days 72 hours 3
Kumulus DF 18836 sulphur M 1 day 24 hours 8
Microthioll Disperss
29487 sulphur M 1 day 24 hours 8
Mission 418 EC
28016 propiconazole 3 38 days 72 hours 3
Nova 40 W 22399 myclobutanil 3 14 days 3
Pristine WG 27985boscalid +
pyraclostrobin7+11 0 days
When dry/29 days2
4
Switch 62.5 WG
28189cyprodinil + fludioxonil
9+12 1 day12
hours/10 days3
3
Topas 250E 30163 propiconazole 3 38 days 72 hours 3
OMAFRA Publication 360, Guide to Fruit Production: Table 5-18. Products Used on Saskatoon Berries
propiconazole
propiconazole – group 3 older chemistry more economical the “glyphosate” of fungicides
systemic fungicide fast uptake and penetration strong translocation. long-lasting preventative and
curative activity
acts on the fungal pathogen leaf penetration haustoria formation
apply early enough to avoid irreversible crop damage and build up of the disease
cyprodinil + fludioxonil
contains two active ingredients; unique and new modes of action cyprodinil - group 9 fludioxonil - group 12
SWITCH® attacks the pathogen at four different sites: inhibits germination of the spore the growth of the germ tube the penetration into the plant growth of the inter and intracellular mycelium
It protects the leaves and fruits from outside and inside
pyraclostrobin + boscalid
two active ingredients that are both highly effective for control pyraclostrobin - group 11
boscalid - group 7
Both ingredients are systemic; move throughout leaf/plant
Pristine inhibits: spore germination
mycelial growth
sporulation of the fungus
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Topaz 250E (also Jade, Mission) relatively cheap
use for initial applications
White tip / petal drop
38 day pre-harvest interval
Switch 62.5 WG expensive, new chemistry
use for final applications
Green fruit / late stage
Based on disease pressure
1 day pre-harvest interval
Pristine WG an alternative to Switch
Pattern of Application V. CULTURAL CONTROL
Organic grower?
Options for chemical-free disease control
May be possible in certain environments
Dryer, cooler regions
Combine with chemical applications as part of an integrated approach
Air Circulation
practices that reduce the duration of surface wetness
less spore germination
achieved by:
controlling weeds
pruning excess suckers
thinning plants
watering at the soil surface
Bio-fungicides
SERENADE MAX unique, patented strain of
Bacillus subtilis (strain QST 713)
30 different lipopeptides that work synergistically to destroy disease pathogens and provide superior antimicrobial activity
Sulfur Kumulus DF (80% sulphur) Microthiol Disperse (80%
sulphur) Residue may impact sales
Sanitation
Break the disease cycle in spring
Remove source of initial inoculum for the following year
Vacuum up leaf litter in the fall
Ensure that all fruit has been picked
X
Disease Forecasting
Use weather data and computer model
Apply fungicide only as needed Reduced cost Less environmental impact
Canadian Journal of Plant PathologyVolume 26, Issue 3, 2004 The development of a dynamic
disease forecasting model to control Entomosporium mespili on Amelanchier alnifolia
Q.A. Holtslag, W.R. Remphrey, W.G.D. Fernando, R.G. St-Pierre & G.H.B. Ash
pages 304-313
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THANKS FOR LISTENING!
QUESTIONS?