Entomosporium Leaf and Berry Spot

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